So now you have installed FreeBSD, and it successfully boots from the hard disk. If you're new to FreeBSD, your first encounter with it can be rather puzzling. You probably didn't expect to see the same things you know from other platforms, but you might not have expected what you see either:
FreeBSD (freebie.example.org) (ttyvO) login:
If you have installed xdm, you'll at least get a
There isn't space in this book to explain everything there is about working with FreeBSD, but in the following few chapters I'd like to make the transition easier for people who have
If you've come from Microsoft, you will notice a large number of differences between UNIX and Microsoft, but in fact the two systems have more in common than meets the eye. Indeed, back in the mid-80s, one of the stated goals of MS-DOS 2.0 was to make it more UNIX-like. You be the judge of how successful that attempt was, but if you know The MS-DOS command-line interface, you'll notice some similarities in the following sections.
In this chapter, we'll look at FreeBSD from the perspective of somebody with computer experience, but with no UNIX background. If you do have a UNIX background, you may still find it interesting.
If you're coming from a Microsoft platform, you'll be used to doing just about everything with a
As a result, the two most important tools you will use with FreeBSD are the shell and the editor. Use the shell to issue direct commands to the system, and the editor to prepare texts. We'll look at these issues in more detail in this chapter. In Chapter 8, Taking control, we'll look at other aspects of the system. First, though, we need to get access to the system.
Probably the biggest difference between most PC operating systems and FreeBSD also takes the longest to get used to: FreeBSD is a multi-user, multi-tasking system. This means that many people can use the system at once, and each can do several things at the same time. You may think "Why would I want to do that?" Once you've got used to this idea, though, you'll never want to do without it again. If you use the X Window System, you'll find that all windows can be active at the same time—you don't have to select them. You can monitor some activity in the background in another window while writing a letter, testing a program, or playing a game.
Before you can access a FreeBSD system, you must be registered as a user. The registration defines a number of parameters:
user name, also often called user ID. This is a name that you use to identify yourself to the systcode.password, a security device to ensure that other people don't abuse your user ID. To log in, you need to specify both your user ID and the correct password. When you type in the password, nothing appears on the screen, so that people looking over your It might seem strange to go to such security measures on a system that you alone use. The
shell, a program that reads in your commands and executes them. MS-DOS uses the program COMMAND.COM to perform this function. UNIX has a large choice of shells: the traditional UNIX shells are the Bourne shell sh and the C shell csh, but FreeBSD also supplies bash, tcsh, zsh and others. I personally use the bash shell, and the examples in this book are based on it.home directory.The system can have multiple users, so each one needs a separate directory in which to store his private files. Typically, users have a directory /home/username, where username is the name they use to login. When you login to the system, the shell sets the ~(tilde) to represent the name of the home directory.group number. UNIX collects users into groups who have specific common Group numbers generally have names associated with them. The group names and numbers are stored in the file /etc/group. In addition, this file may contain user IDs of users who belong to another group, but who are allowed to belong to this group as well.
If you find the concept of groups confusing, don't worry about them. You can get by quite happily without using them at all. You'll just see references to them when we come to discuss file permissions. For further information, look at the man page for Group (5).
By the time you get here, you should have defined a user name, as recommended on page 94. If you haven't, you'll have to login as root and create one as described there.
Once you have a user name, you can log in to the system. Already you have a choice: FreeBSD offers both virtual terminals and the X WindowSystem. The former displays plain text on the monitor, whereas the latter uses the system's graphics capabilities. Once running, you can switch from one to the other, but you have the choice of which interface you use first. If you don't do anything, you get a
It's still relatively uncommon to use xdm, and in many instances you may not want X at all, for example if you're running the system as a server. As a result, we'll look at the "conventional" login first.
If you're logging in on a
login: grog
Password: password doesn't show on the screen
Last login: Fri Apr 11 16:30:04 from canberra
Copyright (c) 1980, 1983, 1986, 1988, 1990, 1991, 1993, 1994
The Regents of the University of California. All rights reserved.
FreeBSD 5.0-RELEASE (FREEBIE) #0: Tue Dec 31 19:08:24 CST 2002
Welcome to FreeBSD!
You have mail.
erase ^H, kill ^U, intr ^C, status ^T
Niklaus Wirth has lamented that, whereas Europeans pronounce his name
correctly (Ni-klows Virt), Americans invariably mangle it into
(Nick-les Worth). Which is to say that Europeans call him by name, but
Americans call him by value.
=== grog@freebie (/dev/ttyv0) ~ 1 ->
There's a lot of stuff here. It's worth looking at it in more detail:
"erase ^H, kill ^U, intr ^C, status ^T" looks strange. It's telling you the current editing The prompt illustrates a number of things about the UNIX environment. By default, sh and friends prompt with a $, and csh and friends prompt with a %. You can change it to just about anything you want with the UNIX shells. You don't have to like my particular version, but it's worth understanding what it's trying to say.
The first part, ===, is just to make it easier to find in a large list on an X display. An xterm window on a
Next, grog@freebie is my user ID and the name of system on which I am working, in the RFC 2822 format used for mail IDs. Multiple systems and multiple users can all be present on a single X display. This way, I can figure out which user I am and what system I am running on.
/dev/ttyv0 is the name of the terminal device. This can sometimes be useful.
~ is the name of the home directory. Most shells, but not all of them, support this symbolism.
1 is the prompt number. Each time you enter a command, it is associated with this number, and the prompt number is incremented. One way to re-execute the command is to enter !!1 (two
To start X from a startx command:
$ startx
If you use xdm, you bypass the
(рис 7.1) KDE display
Either way, assuming that you've installed and configured kde, you'll get a display similar to that in Figure 7-1 . This example includes four windows that are not present on startup. On startup the central part of the screen is empty. We'll look at the windows further below.
KDE is a complicated system, and good documentation is available at http://www.kde.0rg/documentation/. Once you have KDE running, you can access the same information via the help icon on the panel at the bottom (the life ring icon). The following description gives a brief introduction.
The KDE display contains a number of distinct areas. At the top is an optional menu, at the bottom an almost optional panel, and the middle of the screen is reserved for windows.
The Desktop Menu is at the very top of the screen. It provides functionality that is not specific to a particular application. Select the individual categories with the mouse. For example, the New menu looks like this:
(рис 7.2) KDE desktop menu
As the menu indicates, you can use these menus to create new files.
At the bottom of the screen is the panel, which consists of a number of fields. The left-hand section is used for starting applications.
(рис 7.3)
The stylized letter K at the extreme left is the Application Starter. When you select it, a long vertical menu appears at the left of the screen and allows you to start programs ("applications") or access just about any other function.
Next comes an icon called "showdesktop." This is a
The remaining icons on this part of the panel represent various applications.
The next section of the panel contains some control buttons and information about the current desktop layout:
(рис 7.4)
The section at the left shows the current contents of four screens, numbered 1 to 4. Screen 1 is the currently displayed screen; you can select one of the others by moving the cursor in the corresponding direction, or by selecting the field with the mouse.
To the right of that are icons for the currently
The right part of the panel contains a further three fields:
(рис 7.5)
Probably the most useful part of this section of the panel is not very obvious: the right-pointing arrow allows you to remove the panel if you find it's in the way. The entire panel is replaced by a single left-pointing arrow at the extreme right of the display.
By default, kde only uses the left and the right mouse buttons. In general, the
You'll notice that each window has a frame around it with a number of features. In X
If you come from a conventional PC background, you shouldn't have much difficulty with KDE. It's a relatively complete,
UNIX has a very different approach to windows. There is no desktop; just a window manager. It takes up less
Like KDE, you install fvwm2 from the Ports Collection. It's not designed to work completely correctly out of the box, though it does work. As with KDE, the first thing you need to do is to create a .xsession or .xinitrc file, depending on whether you're running xdm. It must contain at least the line:
fvwm2
Start X the same way you did for KDE. This time you see, after starting the same applications as before:
(рис 7.6)
This picture shows both similarities with and differences from KDE. The similarities include:
Still, there are a number of differences as well:
(рис 7.7)
The menus above show one of the problems: look at those system names on the left
When you set up your XF86Config file, you may have specified more than one resolution. For example, on page 107 we selected the additional resolution 1024x768 pixels. When you start X, it automatically selects the first resolution, in this case 640x480. You can change to the previous resolution (the one to the left in the list) by pressing the Ctrl-Alt-Keypad - key, and to the following resolution (the one to the right in the list) with Ctrl-Alt-Keypad +.
You can configure most display boards to display a number of different pixel depths (a different number of bits per pixel, which translates to a different number of colours). When you start X, however, it defaults to 8 bits per pixel (256 colours), which is a very poor
$ Startx ---bpp 32
With older display boards, which had relatively limited
As we saw at the beginning of the chapter, your main tools are the shell and the editor, and that's what we saw on the sample screens. But when you start X, they're not there: you need to start them.
In KDE, you have two ways to start a terminal window:
Run or the Enter key.Obviously the first is the intended approach, and it's easier. Nevertheless, I recommend using xterm at least until you're sure you want to stick with kde: there are some subtle differences, and konsole is intended to work with kde only. If you do stick with KDE, you should change the configuration of the konsole button to start xterm instead; that's relatively straightforward.
In fvwm2, you start an xterm from the left mouse menu, as shown above.
The most basic thing you can do with the shell is to start a program. Consider program names to be commands: like you might ask somebody to "wash the dishes" or "mow the
$ rm filel file2 file3
This starts a program called rm (remove), and gives it a list of three file names to remove.
If you're removing a whole lot of files, this could take a while. Consider removing the entire directory hierarchy /usr/obj, which is created when building a new version of the system (see page 595). This directory hierarchy contains about 15,000 files and directories, and it'll take a while to remove it. You can do this with the following command:
# rm -rf /usr/obj
In this example, we have a couple of options led in by a (-) and also the character at the end of the line.
r option tells rm to recursively descend into f (force) option tells rm to continue on error; otherwise if anything goes wrong, it will stop.rm) to continue after starting the program. It can run for some time, and there's no need to wait for it.In the previous example, we saw a couple of options. By convention, they come between the command name and other parameters, and they're identified because they start with a (-). There's a lot of variation, though, is depending on the individual program.
tar and ps, don't insist on the # ps waux
This command could equally well be written:
# ps –waux
You may also come across programs that refuse to accept the
# tcpdump -i pppO host hub.freebsd.org
Here, ppp0 is an argument to the i option. In some cases, it must be written with a space; in others, it must be written without a space; and in others again, it can be written either way. Pay attention to this detail when reading man pages.
cc -O -pipe -Dinline=rpcgen_inline -Wall –Wno–format-y2K -Wno-uninitialized \-D_FBSDID=_RCSID -c /usr/src/usr.bin/rpcgen/rpc_main.c
With the exception of the last parameter, all of these texts are options, as the
v for verbose output, q for quiet output (i.e. less than normal).-rf? There are a number of solutions for this problem. In this example, you could write:
$ rm ./-rf
This is an alternative file naming convention.
When you invoke a program with the shell, it first parses the input line before passing it to the program: it turns the line into a number of parameters (called arguments in the C programming language). Normally the parameters are separated by white space, either a space or a
$ rm file1 file2 file3
the program receives four arguments, numbered 0 to 3:
| Argument | Value |
|---|---|
| 0 | rm |
| 1 | File1 |
| 2 | File2 |
| 3 | File3 |
What happens if you want to pass a name with a space? For example, you might want to look for the text
"Mail rejected" in a log file. UNIX has a standard program for looking for text, called grep.
The syntax is:
grep expression files
Argument 1 is the expression; all additional arguments are the names of files to search. We could write:
$ grep Mail rejected /var/log/maillog
But that would try to look for the text Mail in the files rejected (probably causing an error message that the file did not exist) and /var/log/maillog (where just about every line contains the text Mail). That's not what we want. Instead, we do pretty much what I wrote above:
$ grep "Mail rejected" /var/log/maillog
In other words, if we put quote characters "" around a group of words, the shell will interpret them as a single parameter. The first parameter that is passed to grep is Mail rejected, not "Mail rejected".
This All_files_updated_since_last_week.
It's even more interesting to see what happens when you pass a globbing character to a program, for example:
$ cc -o foo *.c
This invocation compiles all C source files (*.c) and creates a program foo. If you do this with Microsoft, the C compiler gets four parameters, and it has to find the C source files itself. In UNIX, the shell expands the text *.c and replaces it with the names of the source files. If there are thirty source files in the directory, it will pass a total of 33 parameters to the compiler.
The solution to the "Mail rejected" problem isn't ideal, but it works well enough as long as you don't have to handle fields with blanks in them too often. In many cases, though, particularly in configuration files, fields with blanks are relatively common. As a result, a number of system configuration files use a colon (:) as a delimiter. This looks very confusing at first, but it turns out not to be as bad as the alternatives. We'll see some examples in the PATH
Both UNIX and Microsoft environments store disk data in files, which in turn are placed in directories .A file may be a directory: that is, it may contain other files. The differences between UNIX and Microsoft start with file names. Traditional Microsoft file names are rigid: a file name consists of eight characters, possibly followed by a period and another three characters (the so-called file name extension). There are significant restrictions on which characters may be used to form a file name, and upper and \), which conflicts with other meanings in the C programming language—see page 138 for more details.
FreeBSD has a very fexible method of naming files. File names can contain any character except /, and they can be up to 255 characters long. They are case-sensitive: the names FOO, Foo and foo are three different names. This may seem silly at first, but any alternative means that the names must be associated with a specific character set. How do you upshift the German name $$ ungleichm\ddot\alpha\beta ig$$? What if the same characters appear in a Russian name? Do they still shift the same? The exception is because the / character represents directories. For example, the name /home/fred/longtext-with-a-long-name represent:
First character is a /, representing the root file system.
home is the name of a directory in the root file system.
fred is the name of a directory in /home.
The name suggests that longtext-with-a-long-name is probably a file, not a directory, though you can't tell from the name.
As a result, you can't use / in a file name. In addition, binary 0s (the ASCII NUL character) can confuse a lot of programs. It's almost impossible to get a binary 0 into a file name anyway: that character is used to represent the end of a string in the C programming language, and it's difficult to input it from the keyboard.
Case sensitivity no longer seems as strange as it once did: web browsers have made UNIX file names more popular with Uniform Resource Indicators or URIs, which are derived from UNIX names.
The Microsoft naming convention (name, period and extension) seems similar to that of UNIX. UNIX also uses extensions to represent specific kinds of files. The difference is that these extensions (and their lengths) are implemented by convention, not by the file system. In Microsoft, the period between the name and the extension is a typographical feature that only exists at the display level: it's not part of the name. In UNIX, the period is part of the name, and names like foo.bar.bazzot are perfectly valid file names. The system doesn't assign any particular meaning to file name extensions; instead, it looks for magic numbers, specific values in specific places in the file.
Every directory contains two . and .. (One and two periods). These are relative directory entries: . is an alternative way to refer to the .. refers to the . refers to /home/fred, and .. refers to /home. The .. refers to the same directory. We'll see a number of cases where this is
Most systems have a method of representing groups of file names and other names, usually by using special characters for representing an abstraction. The most common in UNIX are the characters *,? and the []. UNIX calls these characters globbing characters. The Microsoft usage comes from UNIX, but the underlying file name representation makes for big differences. Table 7-2 gives some examples.
| Name | Microsoft meaning | UNIX meaning |
|---|---|---|
| CONFIG.* | All files with the name CONFIG, no matter what their extension. | All files whose name starts with CONFIG., no matter what the rest is. Note that the name contains a period. |
| CONFIG.BA? | All files with the name CONFIG and an extension that starts with BA, no matter what the last character. | All files that start with CONFI.BA and have one more character in their name. |
| * | Depending on the Microsoft version, all files without an extension, or all files. | All files. |
| *.* | All files with an extension. | All files that have a period in the middle of their name. |
| foo[127] | In older versions, invalid. In newer versions with long file name support, the file with the name foo[127]. | The three files foo1, foo2 and foo7. |
Most programs either read
With an interactive shell (one that works on a terminal screen, like we're seeing here), all three files are the same device, in this case the terminal you're working on.
Why two
But of course, even if you're running an interactive shell, you don't want to back up your system to the screen. You need to change stdout to be a file. Many programs can do this themselves; for example, you might make a backup of your home directory like this:
$ tar -cf /var/tmp/backup-
This creates (option c) a file (option f) called /var/tmp/backup, and includes all the files in your home directory (~). Any error messages still appear on the terminal, as stderr hasn't been changed.
This syntax is specific to tar.The shell provides a more general syntax for redirecting input and
$ ls -l drwxr-xr-x 2 root wheel 512 Dec 20 14:36 CVS -rw-r--r-- 1 root wheel 7928 Oct 23 12:01 Makefile -rw-r--r-- 5 root wheel 209 Jul 26 07:11 amd.map -rw-r--r-- 5 root wheel 1163 Jan 31 2002 apmd.conf -rw-r--r-- 5 root wheel 271 Jan 31 2002 auth.conf -rw-r--r-- 1 root wheel 741 Feb 19 2001 crontab -rw-r--r-- 5 root wheel 108 Jan 31 2002 csh.cshrc -rw-r--r-- 5 root wheel 482 Jan 31 2002 csh.login (etc)
You can redirect this output to a file with the command:
$ ls -l > /var/tmp/etclist
This puts the list in the file /var/tmp/etclist. The symbol > tells the shell to redirect stdout to the file whose name follows. Similarly, you could use the < to redirect stdin to that file, for example when using grep to look for specific texts in the file:
$ grep csh < /var/tmp/etclist -rw-r--r-- 5 root wheel 108 Jan 31 2002 csh.cshrc -rw-r--r-- 5 root wheel 482 Jan 31 2002 csh.login -rw-r--r-- 5 grog lemis 110 Jan 31 2002 csh.logout
In fact, though, there's a better way to do that: what we're doing here is feeding the output of a program into the input of another program. That happens so often that there's a special method of doing it, called pipes:
| grep csh -rw-r--r-- 5 root wheel 108 Jan 31 2002 csh.cshrc -rw-r--r-- 5 root wheel 482 Jan 31 2002 csh.login -rw-r--r-- 5 grog lemis 110 Jan 31 2002 csh.logout
The | symbol causes the shell to start two programs. The first has a special file, a pipe, as the output, and the second has the same pipe as input. Nothing gets written to disk, and the result is much faster.
A typical use of pipes is to handle quantities of
$ ls -l | less
Another use is to sort
$ ps aux | sort -n +1
This command takes the output of the ps command and sorts it by the numerical (-n) value of its second column (+1). The first column is numbered 0.
The UNIX
$ export TERM=xterm
This sets the value of the TERM variable to xterm. The word export tells the shell to pass this information to any program it starts. Once it's exported, it stays exported. If the variable isn't exported, only the shell can use it.
Alternatively, if you want to set the variable only once when running a program, and then forget it, you can set it at the beginning of a command line:
$ TERM=xterm-color mutt
This starts the mutt mail reader (see page 474) with xterm's colour features enabled.
For csh and tcsh, set
% setenv TERM xterm
To start a process with these variables, enter:
% env xterm-color mutt
| Name | Purpose |
|---|---|
BLOCKSIZE | The size of blocks that programs like df count. The default is 512 bytes, but it’s often more |
DISPLAY | When running X, the name of the X server. For a local system, this is typically unix:0. For system-name: server-number.screen-number. For the system bumble.example.org, you would probably write bumble.example.org:0. |
EDITOR | The name of your favourite editor. Various programs that start editors look at this variable to know which editor to start. |
HOME | The name of your home directory. |
LANG | The locale that you use. This should be the name of a directory in /usr/share/locale. |
MAIL | Some programs use this variable to find your incoming mail file. |
MANPATH | A list of path names, separated by colons (:), that specifies where the man program should look for man pages. A typical string might be /usr/share/man:/usr/local/man, and specifies that there are many pages in each of the directories /usr/share/man and /usr/local/man. |
NTAPE | The name of the non- |
PATH | A list of path names, separated by colons (:), that specifies where the shell should look for |
PS1 | In Bourne-style shells, this is the prompt string. It’s usually set to $, but can be changed. See page 114 for a discussion of a possible prompt for bash. |
PS2 | In Bourne-style shells, this is the prompt string for continuation lines. It’s usually set to >. |
SHELL | The name of the shell. Some programs use this for starting a shell. |
TAPE | The name of the |
TERM | The type of |
TZ |
Note particularly the PATH variable. One of the most popular questions in the FreeBSD-questions "command not found." This is usually because PATH does not include the
PATH: if you do, you can be subject to security ps in the directory /var/tmp. Despite the name, the program might do something else, for example remove all files in your home directory. If you change directory to /var/tmp and run ps, you will remove all files in your home directory. Obviously much more subtle Instead, run the program like this:
$ ./program
You should set your PATH variable to point to the most common executable directories. Add something like this to your .profile file (for Bourne-style shells):
PATH=/usr/bin:/usr/local/bin:/usr/sbin:/bin:/sbin:/usr/X11R6/bin export PATH
This variable is of great importance: one of the leading problems that PATH variable.
So you can't start a program, and you're wondering whether your PATH echo command:
$ echo $PATH /bin:/usr/bin
The $ at the beginning of $PATH tells the shell to substitute the value of the PATH to echo, which just prints it out.
If you want to print out all the printenv command:
$ printenv | sort BLOCKSIZE=1048576 CLASSPATH=/usr/local/java/lib:/usr/local/java/lib/classes.zip:/hcme/grcg/netscape/ CVSROOT=/home/ncvs DISPLAY=freebie:0 EDITOR=emacs HOME=/home/grog PAGER=less PATH=.:/usr/bin:/usr/sbin:/bin:/sbin:/usr/X11R6/bin:/usr/local/bin:/usr/local/sbin XAUTHORITY=/home/grog/.Xauthority
This example sorts the variables to make it easier to find them. In all probability, you'll find many more variables.
Typing is a pain. If you're anything like me, you're continually making
$ groff -rex=7.5 -r$$ -rL -rW -rN2 -mpic tmac.M unixerf.nm troff: fatal error: can't open 'unixerf.mm': No such file or directory
This command should create the PostScript version of this chapter, but unfortunately I messed up the name of the chapter: it should have been unixref.mm, and I typed unixerf.mm.
Yes, I know this looks terrible. In fact, UNIX has ways to ensure you almost never need to write commands like this. The command I really use to format this chapter is "make unixref".
It would be particularly frustrating if I had to type the whole command in again. UNIX offers a number of ways to make life easier. The most obvious one is so obvious that you tend to take it for granted: the Backspace key erases the last character you entered. Well, most of the time. What if you're running on a machine without a Backspace key? You won't have that problem with a PC, of course, but a lot of workstations have a DEL key instead of a Backspace key. UNIX lets you specify what key to use to erase the last character entered. By default, the erase character really is DEL, but the shell startup changes it and prints out a message saying what it has done:
erase ^H, kill ^U, intr ^C, status ^T
in the example on page 113. ^H (Ctrl-H) is an alternative representation for Backspace.
The three other functions kill, status perform similar editing functions. Kill erases the whole line, and
intr signal called SIGINT to the process. This normally causes a program to stop.
You'll notice that it is set to Ctrl-C, so its function is very similar to that of the MS-DOS Break key. status is an oddball function: it doesn't change the input, it just displays a statistics message. bash doesn't in fact use it: it has a better use for Ctrl-T.
In fact, these
| Name | Default | Function |
|---|---|---|
| CR | \r | Go to beginning of line. Normally, this also terminates input (in other words, it returns the complete line to the program, which then acts on the input). |
| NL | \n | End line. Normally, this also terminates input. |
| Ctrl-C | Generate a SIGINT signal. This normally causes the process to terminate. | |
| QUIT | Ctrl-| | Generate a SIGQUIT signal. This normally causes the process to terminate and |
| ERASE | DEL | Erase last character. FreeBSD sets this to Backspace on login, but under some unusual circumstances you might find it still set to DEL. |
| KILL | Ctrl-U | Erase current input line. |
| EOF | Ctrl-D | Return end-of-file indication. Most programs stop when they receive an EOF. |
| STOP | Ctrl-S | Stop output. Use this to examine text that is scrolling faster than you can read. |
| START | Ctrl-Q | Resume output after stop. |
| SUSP | Ctrl-Z | Suspend process. This key generates a SIGTSTP signal when typed. This normally causes a program to be suspended. To restart, use the fg command |
| DSUSP | Ctrl-Y | Delayed suspend. Generate a SIGTSTP signal when the character is read. Otherwise, this is the same as SUSP. |
| REPRINT | Ctrl-R | Redisplay all characters in the |
| DISCARD | Ctrl-O | Discard all terminal output until another DISCARD character arrives, more input is typed or the program clears the condition. |
To set these characters, use the stty program. For example, if you're used to erasing the complete input line with Ctrl-X, and specifying an end-of-file condition with Ctrl-Z, you could enter:
$ stty susp \377 kill "X eof "Z
You need to set SUSP to something else first, because by default it is Ctrl-Z, so the system wouldn't know which function to perform if you press "Z.
\377 represents the character \0 for the same purpose.
In this particular case, ^X really does mean the character ^ followed by the letter X, and not Ctrl-X, the single character created by holding down the Control character and pressing X at the same time.
Nowadays, most shells supply a command history function and additional functionality for editing it. We'll take a brief look at these features here—for more details see the man pages for your shell.
Shell command line editing has been through a number of evolutionary phases. The original Bourne shell supplied no command line editing at all, though the version supplied with FreeBSD gives you many of the editing features of more modern shells. Still, it's unlikely that you'll want to use the Bourne shell as your shell: bash, ksh, and zsh are all compatible with the Bourne shell, but they also supply better command line editing.
The next phase of command line editing was introduced with the C shell, csh.By modern standards, it's also rather pitiful. It's described in the csh man page if you really want to know. About the only part that is still useful is the ability to repeat a previous command with the !! construct. Modern shells supply command line editing that resembles the editors vi or Emacs. In bash, sh, ksh, and zsh you can make the choice by entering:
$ set -o emacs for Emacs-style editing $ set -o vi for vi-style editing
In tcsh, the corresponding commands are:
% bind emacs % bind vi
Normally you put one of these commands in your startup file.
In Emacs mode, you enter the commands simply by typing them in. In vi mode, you have to press ESC first. Table 7-5 shows an overview of the more typical Emacs-style commands in bash. Many other shells supply similar editing support.
As the name suggests, the Emacs editor understands the same editing characters. It also understands many more commands than are shown here. In addition, many X-based commands, including web browsers, understand some of these characters.
| Key | Function |
|---|---|
| Ctrl-A | Move to the beginning of the line. |
| LeftArrow | Move to previous character on line. |
| Ctrl-B | Move to previous character on line (alternative). |
| Ctrl-D | Delete the character under the cursor. Be careful with this character: it’s also the shell’s end-of-file character, so if you enter it on an empty line, it stops your shell and logs you out. |
| Ctrl-E | Move to the end of the line. |
| RightArrow | Move to next character on line. |
| Ctrl-F | Move to next character on line (alternative). |
| Ctrl-K | Erase the rest of the line. The contents are saved to a ring buffer of erased text and can be restored, possibly elsewhere, with Ctrl-Y. |
| Ctrl-L | Erase screen contents (shell) or redraw window (Emacs). |
| DownArrow | Move to next input line. |
| Ctrl-N | Move to next input line (alternative). |
| UpArrow | Move to previous input line. |
| Ctrl-P | Move to previous input line (alternative). |
| Ctrl-R | Incremental search backward for text. |
| Ctrl-S | Incremental search forward for text. |
| Ctrl-T | Transpose the character under the cursor with the character before the cursor. |
| Ctrl-Y | Insert previously erased with Ctrl-K or Alt-D. |
| Ctrl-_ | Undo the last command. |
| Alt-C | Capitalize the following word. |
| Alt-D | Delete the following word. |
| Alt-F | Move forward one word |
| Alt-L | Convert the following word to |
| Alt-T | Transpose the word before the cursor with the one after it. |
| Alt-U | Convert the following word to |
| Ctrl-X Ctrl-S | Save file (Emacs only). |
| Ctrl-X Ctrl-C | Exit the Emacs editor. |
You'll note a number of alternatives to the cursor keys. There are two reasons for them: firstly, the shell and Emacs must work on systems without arrow keys on the keyboard. The second reason is not immediately obvious: if you're a touch-typer, it's easier to type Ctrl-P than take your hands away from the main keyboard and look for the arrow key. The arrows are good for
As we have seen, UNIX file names can be much longer than traditional Microsoft names, and it becomes a problem to type them correctly. To address this problem, newer shells provide file name completion. In Emacs mode, you typically type in part of the name, then press the Tab key. The shell checks which file names begin with the characters you typed. If there is only one, it puts in the missing characters for you. If there are none, it beeps (rings the "terminal bell"). If there are more than one, it puts in as many letters as are common to all the file names, and then beeps. For example, if I have a directory docco in my home directory, I might enter:
=== grog@freebie (/dev/ttyp4) ~ 14 -> cd docco/ === grog@freebie (/dev/ttyp4) "/docco 15 -> ls freebsd.faq freebsd.fbc freeware === grog@freebie (/dev/ttyp4) "/docco 16 -> emacs freebeepbsd.fbeepaq
Remember that my input is in constant width bold font, and the shell's output is in constant cd doc followed by a Tab character, and the shell completed with the text co/. On the last line, I entered the characters emacs f and a Tab. In this case, the shell determined that there was more than one file name that started like this, so it added the letters ree and rang the bell. I entered the letter b and pressed Tab again, and the shell added the letters sd.f and beeped again. Finally, aq to complete the file name freebsd.faq.
Command line completion in vi mode is similar: instead of pressing Tab, you press ESC twice.
As we saw above, there are a lot of ways to customize your shell. It would be inconvenient to have to set them every time, so all shells provide a means to set them automatically when you login. Nearly every shell has its own startup file. Table 7-6 gives an overview.
| Shell | startup file |
|---|---|
| bash | .profile, then .bashrc |
| csh | .login on login, always .cshrc |
| sh | .profile |
| tcsh | .login on login, always .tcshc, .cshrc if .tcshrc not found |
These files are shell scripts—in other words, straight shell commands. listing 7-1 shows a typical
.bashrc file to set the
umask 022 export BLOCKSIZE=1024 #for df export CVSROCT=/src/ncvs export EDITCR=/opt/bin/emacs export MANPATH=/usr/share/man:/usr/local/man export MCZILLA_HOME=/usr/local/netscape export PAGER=less export PATH=/usr/bin:/usr/local/bin:/usr/sbin:/bin:/sbin:/usr/X11R6/bin PS1="=== \u@\h rtty1) \w \# -> " PS2="\u@\h \w \! ++ " export SHELL=/usr/local/bin/bash export TAPE=/dev/nsa0 #note non-rewinding as standard if [ "$TERM" = "" ]; then export TERM=xterm fi if [ "$DISPLAY" = "" ]; then export DISPLAY=:0 fi /usr/games/fortune # print a fortune cookie
It would be tedious for every user to put settings in their private initialization files, so the shells also read a system-wide default file. For the Bourne shell family, it is /etc/profile, while the C shell family has three files: /etc/csh.login to be executed on login, /etc/csh.cshrc to be executed when a newshell is started after you login, and /etc/csh.logout to be executed when you stop a shell. The start files are executed before the corresponding individual files.
In addition, login classes (page 571) offer another method of setting
The FreeBSD installation gives root a C shell, csh.This is the traditional BSD shell, but it has a number of disadvantages: command line editing is very primitive, and the script language is significantly different from that of the Bourne shell, which is the de facto standard for shell scripts: if you stay with the C shell, you may still need to understand the Bourne shell. The latest version of the Bourne shell sh also includes some command line editing. See page 133 for details of how to enable it.
If you want to stay with a csh-like shell, you can get better command line editing with tcsh, which is also in the base system. You can get both better command line editing and Bourne shell syntax with bash, in the Ports Collection.
If you have root access, you can use vipw to change your shell, but there's a more general way: use chsh (ChangeShell). Simply run the program. It starts your favourite editor (as defined by the EDITOR
#Changing user database information for velte. Shell: /bin/csh Full Name: Jack Velte Location: Office Phone: Home Phone:
You can change anything after the colons. For example, you might change this to:
#Changing user database information for velte. Shell: /usr/local/bin/bash Full Name: Jack Velte Location: On the road Office Phone: +1-408-555-1999 Home Phone:
chsh checks and updates the password files when you save the modifications and exit the editor. The next time you login, you get the new shell. chsh tries to ensure you don't make any
bumble# su velte Password: su-2.00$ note the newprompt
You might hear objections to using bash as a root shell. The argument goes something like this: bash is installed in /usr/local/bin, so it's not available if you boot into single-user mode, where only the root file system is available. Even if you copy it to, say, /bin, you can't run it in single-user mode because it needs libraries in /usr/lib.
In fact, this isn't a problem. If you install the system the way I recommend in Chapter 5, /usr is on the root file system. Even if it isn't, though, you don't have to use bash in single-user mode. When you boot to single-user mode, you get a prompt asking you which shell to start, and suggesting /bin/sh.
If you're coming from a Microsoft background, there are a few got chas that you might trip over.
/ (slash) and \ (backslash) are confusing. As we've seen, UNIX uses / to delimit directories. The backslash \ is called an escape character. It has, several purposes:
Mail rejected to "Mail rejected" to stop the shell from interpreting it. We could also have written: Mail\ rejected.
A more common use for this quoting is to tell the shell to ignore the end of a line. If acommand line in a shell script gets too long, you might like to split it up into several lines; but the shell sees the end of a line as a go-ahead to perform the command. Stop it from doing so by putting a backslash immediately before the end of the line:
$ grep \ "Mail rejected" \ /var/log/maillog
Don't put any spaces between the \ and the end of the line; otherwise the shell will interpret the first space as a parameter by itself, and then it will interpret the end of line as the end of the command.
\n means "new line." This usage appears in many other places as well.\ as an escape character causes problems: how do we put a \ character on a line? The answer: quote it. Write \\ when you mean \. This causes particular problems when interfacing with Microsoft: if you give a Microsoft path name to a shell, it needs the doubled backslashes: C:\\WINDOWS.We've seen that the shell treats "white space," either spaces or tab characters, as the same. Unfortunately, some other programs do not. make, sendmail and syslogd make a distinction between the two kinds of characters, and they all require tabs (not spaces) in certain places. This is a real nuisance, because hardly any editor makes a distinction between them.
In the olden days, the standard computer terminal was a Teletype, a kind of computer-controlled electric type writer. When the carriage, which contained the print head, got to the end of a line, it required two mechanical operations to move to the beginning of the next line: the carriage return
Generations of computer systems emulated this \n.
This causes problems transferring data between FreeBSD and Microsoft, and also when printings to printers that still expect both characters. We'll look at the file transfer issues on page 260 and the printer issues on page 267.
A part from the shell, your second most important tool is the editor, a program that creates and changes texts. Another divergence of concept between UNIX and Microsoft environments is that UNIX gives you a choice of editors in just about anything you do. Microsoft products frequently try to redefine the whole environment, so if you change mailers, you may also have to change the editor you use to write mail. This has a profound effect on the way you work. In particular, the Microsoft way makes it uninteresting to write a really good editor, because you can't use it all the time.
The standard BSD editor is vi, about which people speak with a mixture of admiration, awe and horror. vi is one of the oldest parts of BSD. It is a very powerful editor, but nobody would say that it is easy to learn. There are two reasons to use vi:
If, on the other hand, you don't know vi, and you only work on systems whose software you can control, you probably shouldn't use vi. Emacs is much easier to learn, and it is more powerful than vi.
(рис 7.8) Emacs main menu
When running under X, Emacs displays its own window (v/' uses an xterm under these circumstances). As are sult, if you start Emacs from an xterm, you should use the character to start it in the background:
$ emacs
Figure 7-8 shows the resulting display. As you can see, the first thing that Emacs offers you is a tutorial. You should take it. You'll also notice the menu bars at the top. Although they look primitive compared to graphics toolbars, they offer all the functionality of graphics-oriented menus. In addition, they will tell you the keystrokes that you can use to invoke the same functions. Figure 7-9 gives an example of the Files menu.
There is a lot of documentation for Emacs, much of it on line. The complete Emacs
(рис 7.9) Emacs files menu
To stop X, press the key combination Ctrl-Alt-Backspace, which is deliberately chosen to resemble the key combination Ctrl-Alt-Delete used to reboot the machine. Ctrl-Alt-Backspace stops X and returns you to the
To stop the system, use the shutdown program. To do so, you need to be a member of group operator.
By default, KDE uses the halt program. Only root can use this program, so you should reconfigure KDE to use shutdown. After this, you can shut down from KDE with the
So now you have installed FreeBSD, and it successfully boots from the hard disk. If you're new to FreeBSD, your first encounter with it can be rather puzzling. You probably didn't expect to see the same things you know from other platforms, but you might not have expected what you see either:
FreeBSD (freebie.example.org) (ttyvO) login:
If you have installed xdm, you'll at least get a
There isn't space in this book to explain everything there is about working with FreeBSD, but in the following few chapters I'd like to make the transition easier for people who have
If you've come from Microsoft, you will notice a large number of differences between UNIX and Microsoft, but in fact the two systems have more in common than meets the eye. Indeed, back in the mid-80s, one of the stated goals of MS-DOS 2.0 was to make it more UNIX-like. You be the judge of how successful that attempt was, but if you know The MS-DOS command-line interface, you'll notice some similarities in the following sections.
In this chapter, we'll look at FreeBSD from the perspective of somebody with computer experience, but with no UNIX background. If you do have a UNIX background, you may still find it interesting.
If you're coming from a Microsoft platform, you'll be used to doing just about everything with a
As a result, the two most important tools you will use with FreeBSD are the shell and the editor. Use the shell to issue direct commands to the system, and the editor to prepare texts. We'll look at these issues in more detail in this chapter. In Chapter 8, Taking control, we'll look at other aspects of the system. First, though, we need to get access to the system.
Probably the biggest difference between most PC operating systems and FreeBSD also takes the longest to get used to: FreeBSD is a multi-user, multi-tasking system. This means that many people can use the system at once, and each can do several things at the same time. You may think "Why would I want to do that?" Once you've got used to this idea, though, you'll never want to do without it again. If you use the X Window System, you'll find that all windows can be active at the same time—you don't have to select them. You can monitor some activity in the background in another window while writing a letter, testing a program, or playing a game.
Before you can access a FreeBSD system, you must be registered as a user. The registration defines a number of parameters:
user name, also often called user ID. This is a name that you use to identify yourself to the systcode.password, a security device to ensure that other people don't abuse your user ID. To log in, you need to specify both your user ID and the correct password. When you type in the password, nothing appears on the screen, so that people looking over your It might seem strange to go to such security measures on a system that you alone use. The
shell, a program that reads in your commands and executes them. MS-DOS uses the program COMMAND.COM to perform this function. UNIX has a large choice of shells: the traditional UNIX shells are the Bourne shell sh and the C shell csh, but FreeBSD also supplies bash, tcsh, zsh and others. I personally use the bash shell, and the examples in this book are based on it.home directory.The system can have multiple users, so each one needs a separate directory in which to store his private files. Typically, users have a directory /home/username, where username is the name they use to login. When you login to the system, the shell sets the ~(tilde) to represent the name of the home directory.group number. UNIX collects users into groups who have specific common Group numbers generally have names associated with them. The group names and numbers are stored in the file /etc/group. In addition, this file may contain user IDs of users who belong to another group, but who are allowed to belong to this group as well.
If you find the concept of groups confusing, don't worry about them. You can get by quite happily without using them at all. You'll just see references to them when we come to discuss file permissions. For further information, look at the man page for Group (5).
By the time you get here, you should have defined a user name, as recommended on page 94. If you haven't, you'll have to login as root and create one as described there.
Once you have a user name, you can log in to the system. Already you have a choice: FreeBSD offers both virtual terminals and the X WindowSystem. The former displays plain text on the monitor, whereas the latter uses the system's graphics capabilities. Once running, you can switch from one to the other, but you have the choice of which interface you use first. If you don't do anything, you get a
It's still relatively uncommon to use xdm, and in many instances you may not want X at all, for example if you're running the system as a server. As a result, we'll look at the "conventional" login first.
If you're logging in on a
login: grog
Password: password doesn't show on the screen
Last login: Fri Apr 11 16:30:04 from canberra
Copyright (c) 1980, 1983, 1986, 1988, 1990, 1991, 1993, 1994
The Regents of the University of California. All rights reserved.
FreeBSD 5.0-RELEASE (FREEBIE) #0: Tue Dec 31 19:08:24 CST 2002
Welcome to FreeBSD!
You have mail.
erase ^H, kill ^U, intr ^C, status ^T
Niklaus Wirth has lamented that, whereas Europeans pronounce his name
correctly (Ni-klows Virt), Americans invariably mangle it into
(Nick-les Worth). Which is to say that Europeans call him by name, but
Americans call him by value.
=== grog@freebie (/dev/ttyv0) ~ 1 ->
There's a lot of stuff here. It's worth looking at it in more detail:
"erase ^H, kill ^U, intr ^C, status ^T" looks strange. It's telling you the current editing The prompt illustrates a number of things about the UNIX environment. By default, sh and friends prompt with a $, and csh and friends prompt with a %. You can change it to just about anything you want with the UNIX shells. You don't have to like my particular version, but it's worth understanding what it's trying to say.
The first part, ===, is just to make it easier to find in a large list on an X display. An xterm window on a
Next, grog@freebie is my user ID and the name of system on which I am working, in the RFC 2822 format used for mail IDs. Multiple systems and multiple users can all be present on a single X display. This way, I can figure out which user I am and what system I am running on.
/dev/ttyv0 is the name of the terminal device. This can sometimes be useful.
~ is the name of the home directory. Most shells, but not all of them, support this symbolism.
1 is the prompt number. Each time you enter a command, it is associated with this number, and the prompt number is incremented. One way to re-execute the command is to enter !!1 (two
To start X from a startx command:
$ startx
If you use xdm, you bypass the
(рис 7.1) KDE display
Either way, assuming that you've installed and configured kde, you'll get a display similar to that in Figure 7-1 . This example includes four windows that are not present on startup. On startup the central part of the screen is empty. We'll look at the windows further below.
KDE is a complicated system, and good documentation is available at http://www.kde.0rg/documentation/. Once you have KDE running, you can access the same information via the help icon on the panel at the bottom (the life ring icon). The following description gives a brief introduction.
The KDE display contains a number of distinct areas. At the top is an optional menu, at the bottom an almost optional panel, and the middle of the screen is reserved for windows.
The Desktop Menu is at the very top of the screen. It provides functionality that is not specific to a particular application. Select the individual categories with the mouse. For example, the New menu looks like this:
(рис 7.2) KDE desktop menu
As the menu indicates, you can use these menus to create new files.
At the bottom of the screen is the panel, which consists of a number of fields. The left-hand section is used for starting applications.
(рис 7.3)
The stylized letter K at the extreme left is the Application Starter. When you select it, a long vertical menu appears at the left of the screen and allows you to start programs ("applications") or access just about any other function.
Next comes an icon called "showdesktop." This is a
The remaining icons on this part of the panel represent various applications.
The next section of the panel contains some control buttons and information about the current desktop layout:
(рис 7.4)
The section at the left shows the current contents of four screens, numbered 1 to 4. Screen 1 is the currently displayed screen; you can select one of the others by moving the cursor in the corresponding direction, or by selecting the field with the mouse.
To the right of that are icons for the currently
The right part of the panel contains a further three fields:
(рис 7.5)
Probably the most useful part of this section of the panel is not very obvious: the right-pointing arrow allows you to remove the panel if you find it's in the way. The entire panel is replaced by a single left-pointing arrow at the extreme right of the display.
By default, kde only uses the left and the right mouse buttons. In general, the
You'll notice that each window has a frame around it with a number of features. In X
If you come from a conventional PC background, you shouldn't have much difficulty with KDE. It's a relatively complete,
UNIX has a very different approach to windows. There is no desktop; just a window manager. It takes up less
Like KDE, you install fvwm2 from the Ports Collection. It's not designed to work completely correctly out of the box, though it does work. As with KDE, the first thing you need to do is to create a .xsession or .xinitrc file, depending on whether you're running xdm. It must contain at least the line:
fvwm2
Start X the same way you did for KDE. This time you see, after starting the same applications as before:
(рис 7.6)
This picture shows both similarities with and differences from KDE. The similarities include:
Still, there are a number of differences as well:
(рис 7.7)
The menus above show one of the problems: look at those system names on the left
When you set up your XF86Config file, you may have specified more than one resolution. For example, on page 107 we selected the additional resolution 1024x768 pixels. When you start X, it automatically selects the first resolution, in this case 640x480. You can change to the previous resolution (the one to the left in the list) by pressing the Ctrl-Alt-Keypad - key, and to the following resolution (the one to the right in the list) with Ctrl-Alt-Keypad +.
You can configure most display boards to display a number of different pixel depths (a different number of bits per pixel, which translates to a different number of colours). When you start X, however, it defaults to 8 bits per pixel (256 colours), which is a very poor
$ Startx ---bpp 32
With older display boards, which had relatively limited
As we saw at the beginning of the chapter, your main tools are the shell and the editor, and that's what we saw on the sample screens. But when you start X, they're not there: you need to start them.
In KDE, you have two ways to start a terminal window:
Run or the Enter key.Obviously the first is the intended approach, and it's easier. Nevertheless, I recommend using xterm at least until you're sure you want to stick with kde: there are some subtle differences, and konsole is intended to work with kde only. If you do stick with KDE, you should change the configuration of the konsole button to start xterm instead; that's relatively straightforward.
In fvwm2, you start an xterm from the left mouse menu, as shown above.
The most basic thing you can do with the shell is to start a program. Consider program names to be commands: like you might ask somebody to "wash the dishes" or "mow the
$ rm filel file2 file3
This starts a program called rm (remove), and gives it a list of three file names to remove.
If you're removing a whole lot of files, this could take a while. Consider removing the entire directory hierarchy /usr/obj, which is created when building a new version of the system (see page 595). This directory hierarchy contains about 15,000 files and directories, and it'll take a while to remove it. You can do this with the following command:
# rm -rf /usr/obj
In this example, we have a couple of options led in by a (-) and also the character at the end of the line.
r option tells rm to recursively descend into f (force) option tells rm to continue on error; otherwise if anything goes wrong, it will stop.rm) to continue after starting the program. It can run for some time, and there's no need to wait for it.In the previous example, we saw a couple of options. By convention, they come between the command name and other parameters, and they're identified because they start with a (-). There's a lot of variation, though, is depending on the individual program.
tar and ps, don't insist on the # ps waux
This command could equally well be written:
# ps –waux
You may also come across programs that refuse to accept the
# tcpdump -i pppO host hub.freebsd.org
Here, ppp0 is an argument to the i option. In some cases, it must be written with a space; in others, it must be written without a space; and in others again, it can be written either way. Pay attention to this detail when reading man pages.
cc -O -pipe -Dinline=rpcgen_inline -Wall –Wno–format-y2K -Wno-uninitialized \-D_FBSDID=_RCSID -c /usr/src/usr.bin/rpcgen/rpc_main.c
With the exception of the last parameter, all of these texts are options, as the
v for verbose output, q for quiet output (i.e. less than normal).-rf? There are a number of solutions for this problem. In this example, you could write:
$ rm ./-rf
This is an alternative file naming convention.
When you invoke a program with the shell, it first parses the input line before passing it to the program: it turns the line into a number of parameters (called arguments in the C programming language). Normally the parameters are separated by white space, either a space or a
$ rm file1 file2 file3
the program receives four arguments, numbered 0 to 3:
| Argument | Value |
|---|---|
| 0 | rm |
| 1 | File1 |
| 2 | File2 |
| 3 | File3 |
What happens if you want to pass a name with a space? For example, you might want to look for the text
"Mail rejected" in a log file. UNIX has a standard program for looking for text, called grep.
The syntax is:
grep expression files
Argument 1 is the expression; all additional arguments are the names of files to search. We could write:
$ grep Mail rejected /var/log/maillog
But that would try to look for the text Mail in the files rejected (probably causing an error message that the file did not exist) and /var/log/maillog (where just about every line contains the text Mail). That's not what we want. Instead, we do pretty much what I wrote above:
$ grep "Mail rejected" /var/log/maillog
In other words, if we put quote characters "" around a group of words, the shell will interpret them as a single parameter. The first parameter that is passed to grep is Mail rejected, not "Mail rejected".
This All_files_updated_since_last_week.
It's even more interesting to see what happens when you pass a globbing character to a program, for example:
$ cc -o foo *.c
This invocation compiles all C source files (*.c) and creates a program foo. If you do this with Microsoft, the C compiler gets four parameters, and it has to find the C source files itself. In UNIX, the shell expands the text *.c and replaces it with the names of the source files. If there are thirty source files in the directory, it will pass a total of 33 parameters to the compiler.
The solution to the "Mail rejected" problem isn't ideal, but it works well enough as long as you don't have to handle fields with blanks in them too often. In many cases, though, particularly in configuration files, fields with blanks are relatively common. As a result, a number of system configuration files use a colon (:) as a delimiter. This looks very confusing at first, but it turns out not to be as bad as the alternatives. We'll see some examples in the PATH
Both UNIX and Microsoft environments store disk data in files, which in turn are placed in directories .A file may be a directory: that is, it may contain other files. The differences between UNIX and Microsoft start with file names. Traditional Microsoft file names are rigid: a file name consists of eight characters, possibly followed by a period and another three characters (the so-called file name extension). There are significant restrictions on which characters may be used to form a file name, and upper and \), which conflicts with other meanings in the C programming language—see page 138 for more details.
FreeBSD has a very fexible method of naming files. File names can contain any character except /, and they can be up to 255 characters long. They are case-sensitive: the names FOO, Foo and foo are three different names. This may seem silly at first, but any alternative means that the names must be associated with a specific character set. How do you upshift the German name $$ ungleichm\ddot\alpha\beta ig$$? What if the same characters appear in a Russian name? Do they still shift the same? The exception is because the / character represents directories. For example, the name /home/fred/longtext-with-a-long-name represent:
First character is a /, representing the root file system.
home is the name of a directory in the root file system.
fred is the name of a directory in /home.
The name suggests that longtext-with-a-long-name is probably a file, not a directory, though you can't tell from the name.
As a result, you can't use / in a file name. In addition, binary 0s (the ASCII NUL character) can confuse a lot of programs. It's almost impossible to get a binary 0 into a file name anyway: that character is used to represent the end of a string in the C programming language, and it's difficult to input it from the keyboard.
Case sensitivity no longer seems as strange as it once did: web browsers have made UNIX file names more popular with Uniform Resource Indicators or URIs, which are derived from UNIX names.
The Microsoft naming convention (name, period and extension) seems similar to that of UNIX. UNIX also uses extensions to represent specific kinds of files. The difference is that these extensions (and their lengths) are implemented by convention, not by the file system. In Microsoft, the period between the name and the extension is a typographical feature that only exists at the display level: it's not part of the name. In UNIX, the period is part of the name, and names like foo.bar.bazzot are perfectly valid file names. The system doesn't assign any particular meaning to file name extensions; instead, it looks for magic numbers, specific values in specific places in the file.
Every directory contains two . and .. (One and two periods). These are relative directory entries: . is an alternative way to refer to the .. refers to the . refers to /home/fred, and .. refers to /home. The .. refers to the same directory. We'll see a number of cases where this is
Most systems have a method of representing groups of file names and other names, usually by using special characters for representing an abstraction. The most common in UNIX are the characters *,? and the []. UNIX calls these characters globbing characters. The Microsoft usage comes from UNIX, but the underlying file name representation makes for big differences. Table 7-2 gives some examples.
| Name | Microsoft meaning | UNIX meaning |
|---|---|---|
| CONFIG.* | All files with the name CONFIG, no matter what their extension. | All files whose name starts with CONFIG., no matter what the rest is. Note that the name contains a period. |
| CONFIG.BA? | All files with the name CONFIG and an extension that starts with BA, no matter what the last character. | All files that start with CONFI.BA and have one more character in their name. |
| * | Depending on the Microsoft version, all files without an extension, or all files. | All files. |
| *.* | All files with an extension. | All files that have a period in the middle of their name. |
| foo[127] | In older versions, invalid. In newer versions with long file name support, the file with the name foo[127]. | The three files foo1, foo2 and foo7. |
Most programs either read
With an interactive shell (one that works on a terminal screen, like we're seeing here), all three files are the same device, in this case the terminal you're working on.
Why two
But of course, even if you're running an interactive shell, you don't want to back up your system to the screen. You need to change stdout to be a file. Many programs can do this themselves; for example, you might make a backup of your home directory like this:
$ tar -cf /var/tmp/backup-
This creates (option c) a file (option f) called /var/tmp/backup, and includes all the files in your home directory (~). Any error messages still appear on the terminal, as stderr hasn't been changed.
This syntax is specific to tar.The shell provides a more general syntax for redirecting input and
$ ls -l drwxr-xr-x 2 root wheel 512 Dec 20 14:36 CVS -rw-r--r-- 1 root wheel 7928 Oct 23 12:01 Makefile -rw-r--r-- 5 root wheel 209 Jul 26 07:11 amd.map -rw-r--r-- 5 root wheel 1163 Jan 31 2002 apmd.conf -rw-r--r-- 5 root wheel 271 Jan 31 2002 auth.conf -rw-r--r-- 1 root wheel 741 Feb 19 2001 crontab -rw-r--r-- 5 root wheel 108 Jan 31 2002 csh.cshrc -rw-r--r-- 5 root wheel 482 Jan 31 2002 csh.login (etc)
You can redirect this output to a file with the command:
$ ls -l > /var/tmp/etclist
This puts the list in the file /var/tmp/etclist. The symbol > tells the shell to redirect stdout to the file whose name follows. Similarly, you could use the < to redirect stdin to that file, for example when using grep to look for specific texts in the file:
$ grep csh < /var/tmp/etclist -rw-r--r-- 5 root wheel 108 Jan 31 2002 csh.cshrc -rw-r--r-- 5 root wheel 482 Jan 31 2002 csh.login -rw-r--r-- 5 grog lemis 110 Jan 31 2002 csh.logout
In fact, though, there's a better way to do that: what we're doing here is feeding the output of a program into the input of another program. That happens so often that there's a special method of doing it, called pipes:
| grep csh -rw-r--r-- 5 root wheel 108 Jan 31 2002 csh.cshrc -rw-r--r-- 5 root wheel 482 Jan 31 2002 csh.login -rw-r--r-- 5 grog lemis 110 Jan 31 2002 csh.logout
The | symbol causes the shell to start two programs. The first has a special file, a pipe, as the output, and the second has the same pipe as input. Nothing gets written to disk, and the result is much faster.
A typical use of pipes is to handle quantities of
$ ls -l | less
Another use is to sort
$ ps aux | sort -n +1
This command takes the output of the ps command and sorts it by the numerical (-n) value of its second column (+1). The first column is numbered 0.
The UNIX
$ export TERM=xterm
This sets the value of the TERM variable to xterm. The word export tells the shell to pass this information to any program it starts. Once it's exported, it stays exported. If the variable isn't exported, only the shell can use it.
Alternatively, if you want to set the variable only once when running a program, and then forget it, you can set it at the beginning of a command line:
$ TERM=xterm-color mutt
This starts the mutt mail reader (see page 474) with xterm's colour features enabled.
For csh and tcsh, set
% setenv TERM xterm
To start a process with these variables, enter:
% env xterm-color mutt
| Name | Purpose |
|---|---|
BLOCKSIZE | The size of blocks that programs like df count. The default is 512 bytes, but it’s often more |
DISPLAY | When running X, the name of the X server. For a local system, this is typically unix:0. For system-name: server-number.screen-number. For the system bumble.example.org, you would probably write bumble.example.org:0. |
EDITOR | The name of your favourite editor. Various programs that start editors look at this variable to know which editor to start. |
HOME | The name of your home directory. |
LANG | The locale that you use. This should be the name of a directory in /usr/share/locale. |
MAIL | Some programs use this variable to find your incoming mail file. |
MANPATH | A list of path names, separated by colons (:), that specifies where the man program should look for man pages. A typical string might be /usr/share/man:/usr/local/man, and specifies that there are many pages in each of the directories /usr/share/man and /usr/local/man. |
NTAPE | The name of the non- |
PATH | A list of path names, separated by colons (:), that specifies where the shell should look for |
PS1 | In Bourne-style shells, this is the prompt string. It’s usually set to $, but can be changed. See page 114 for a discussion of a possible prompt for bash. |
PS2 | In Bourne-style shells, this is the prompt string for continuation lines. It’s usually set to >. |
SHELL | The name of the shell. Some programs use this for starting a shell. |
TAPE | The name of the |
TERM | The type of |
TZ |
Note particularly the PATH variable. One of the most popular questions in the FreeBSD-questions "command not found." This is usually because PATH does not include the
PATH: if you do, you can be subject to security ps in the directory /var/tmp. Despite the name, the program might do something else, for example remove all files in your home directory. If you change directory to /var/tmp and run ps, you will remove all files in your home directory. Obviously much more subtle Instead, run the program like this:
$ ./program
You should set your PATH variable to point to the most common executable directories. Add something like this to your .profile file (for Bourne-style shells):
PATH=/usr/bin:/usr/local/bin:/usr/sbin:/bin:/sbin:/usr/X11R6/bin export PATH
This variable is of great importance: one of the leading problems that PATH variable.
So you can't start a program, and you're wondering whether your PATH echo command:
$ echo $PATH /bin:/usr/bin
The $ at the beginning of $PATH tells the shell to substitute the value of the PATH to echo, which just prints it out.
If you want to print out all the printenv command:
$ printenv | sort BLOCKSIZE=1048576 CLASSPATH=/usr/local/java/lib:/usr/local/java/lib/classes.zip:/hcme/grcg/netscape/ CVSROOT=/home/ncvs DISPLAY=freebie:0 EDITOR=emacs HOME=/home/grog PAGER=less PATH=.:/usr/bin:/usr/sbin:/bin:/sbin:/usr/X11R6/bin:/usr/local/bin:/usr/local/sbin XAUTHORITY=/home/grog/.Xauthority
This example sorts the variables to make it easier to find them. In all probability, you'll find many more variables.
Typing is a pain. If you're anything like me, you're continually making
$ groff -rex=7.5 -r$$ -rL -rW -rN2 -mpic tmac.M unixerf.nm troff: fatal error: can't open 'unixerf.mm': No such file or directory
This command should create the PostScript version of this chapter, but unfortunately I messed up the name of the chapter: it should have been unixref.mm, and I typed unixerf.mm.
Yes, I know this looks terrible. In fact, UNIX has ways to ensure you almost never need to write commands like this. The command I really use to format this chapter is "make unixref".
It would be particularly frustrating if I had to type the whole command in again. UNIX offers a number of ways to make life easier. The most obvious one is so obvious that you tend to take it for granted: the Backspace key erases the last character you entered. Well, most of the time. What if you're running on a machine without a Backspace key? You won't have that problem with a PC, of course, but a lot of workstations have a DEL key instead of a Backspace key. UNIX lets you specify what key to use to erase the last character entered. By default, the erase character really is DEL, but the shell startup changes it and prints out a message saying what it has done:
erase ^H, kill ^U, intr ^C, status ^T
in the example on page 113. ^H (Ctrl-H) is an alternative representation for Backspace.
The three other functions kill, status perform similar editing functions. Kill erases the whole line, and
intr signal called SIGINT to the process. This normally causes a program to stop.
You'll notice that it is set to Ctrl-C, so its function is very similar to that of the MS-DOS Break key. status is an oddball function: it doesn't change the input, it just displays a statistics message. bash doesn't in fact use it: it has a better use for Ctrl-T.
In fact, these
| Name | Default | Function |
|---|---|---|
| CR | \r | Go to beginning of line. Normally, this also terminates input (in other words, it returns the complete line to the program, which then acts on the input). |
| NL | \n | End line. Normally, this also terminates input. |
| Ctrl-C | Generate a SIGINT signal. This normally causes the process to terminate. | |
| QUIT | Ctrl-| | Generate a SIGQUIT signal. This normally causes the process to terminate and |
| ERASE | DEL | Erase last character. FreeBSD sets this to Backspace on login, but under some unusual circumstances you might find it still set to DEL. |
| KILL | Ctrl-U | Erase current input line. |
| EOF | Ctrl-D | Return end-of-file indication. Most programs stop when they receive an EOF. |
| STOP | Ctrl-S | Stop output. Use this to examine text that is scrolling faster than you can read. |
| START | Ctrl-Q | Resume output after stop. |
| SUSP | Ctrl-Z | Suspend process. This key generates a SIGTSTP signal when typed. This normally causes a program to be suspended. To restart, use the fg command |
| DSUSP | Ctrl-Y | Delayed suspend. Generate a SIGTSTP signal when the character is read. Otherwise, this is the same as SUSP. |
| REPRINT | Ctrl-R | Redisplay all characters in the |
| DISCARD | Ctrl-O | Discard all terminal output until another DISCARD character arrives, more input is typed or the program clears the condition. |
To set these characters, use the stty program. For example, if you're used to erasing the complete input line with Ctrl-X, and specifying an end-of-file condition with Ctrl-Z, you could enter:
$ stty susp \377 kill "X eof "Z
You need to set SUSP to something else first, because by default it is Ctrl-Z, so the system wouldn't know which function to perform if you press "Z.
\377 represents the character \0 for the same purpose.
In this particular case, ^X really does mean the character ^ followed by the letter X, and not Ctrl-X, the single character created by holding down the Control character and pressing X at the same time.
Nowadays, most shells supply a command history function and additional functionality for editing it. We'll take a brief look at these features here—for more details see the man pages for your shell.
Shell command line editing has been through a number of evolutionary phases. The original Bourne shell supplied no command line editing at all, though the version supplied with FreeBSD gives you many of the editing features of more modern shells. Still, it's unlikely that you'll want to use the Bourne shell as your shell: bash, ksh, and zsh are all compatible with the Bourne shell, but they also supply better command line editing.
The next phase of command line editing was introduced with the C shell, csh.By modern standards, it's also rather pitiful. It's described in the csh man page if you really want to know. About the only part that is still useful is the ability to repeat a previous command with the !! construct. Modern shells supply command line editing that resembles the editors vi or Emacs. In bash, sh, ksh, and zsh you can make the choice by entering:
$ set -o emacs for Emacs-style editing $ set -o vi for vi-style editing
In tcsh, the corresponding commands are:
% bind emacs % bind vi
Normally you put one of these commands in your startup file.
In Emacs mode, you enter the commands simply by typing them in. In vi mode, you have to press ESC first. Table 7-5 shows an overview of the more typical Emacs-style commands in bash. Many other shells supply similar editing support.
As the name suggests, the Emacs editor understands the same editing characters. It also understands many more commands than are shown here. In addition, many X-based commands, including web browsers, understand some of these characters.
| Key | Function |
|---|---|
| Ctrl-A | Move to the beginning of the line. |
| LeftArrow | Move to previous character on line. |
| Ctrl-B | Move to previous character on line (alternative). |
| Ctrl-D | Delete the character under the cursor. Be careful with this character: it’s also the shell’s end-of-file character, so if you enter it on an empty line, it stops your shell and logs you out. |
| Ctrl-E | Move to the end of the line. |
| RightArrow | Move to next character on line. |
| Ctrl-F | Move to next character on line (alternative). |
| Ctrl-K | Erase the rest of the line. The contents are saved to a ring buffer of erased text and can be restored, possibly elsewhere, with Ctrl-Y. |
| Ctrl-L | Erase screen contents (shell) or redraw window (Emacs). |
| DownArrow | Move to next input line. |
| Ctrl-N | Move to next input line (alternative). |
| UpArrow | Move to previous input line. |
| Ctrl-P | Move to previous input line (alternative). |
| Ctrl-R | Incremental search backward for text. |
| Ctrl-S | Incremental search forward for text. |
| Ctrl-T | Transpose the character under the cursor with the character before the cursor. |
| Ctrl-Y | Insert previously erased with Ctrl-K or Alt-D. |
| Ctrl-_ | Undo the last command. |
| Alt-C | Capitalize the following word. |
| Alt-D | Delete the following word. |
| Alt-F | Move forward one word |
| Alt-L | Convert the following word to |
| Alt-T | Transpose the word before the cursor with the one after it. |
| Alt-U | Convert the following word to |
| Ctrl-X Ctrl-S | Save file (Emacs only). |
| Ctrl-X Ctrl-C | Exit the Emacs editor. |
You'll note a number of alternatives to the cursor keys. There are two reasons for them: firstly, the shell and Emacs must work on systems without arrow keys on the keyboard. The second reason is not immediately obvious: if you're a touch-typer, it's easier to type Ctrl-P than take your hands away from the main keyboard and look for the arrow key. The arrows are good for
As we have seen, UNIX file names can be much longer than traditional Microsoft names, and it becomes a problem to type them correctly. To address this problem, newer shells provide file name completion. In Emacs mode, you typically type in part of the name, then press the Tab key. The shell checks which file names begin with the characters you typed. If there is only one, it puts in the missing characters for you. If there are none, it beeps (rings the "terminal bell"). If there are more than one, it puts in as many letters as are common to all the file names, and then beeps. For example, if I have a directory docco in my home directory, I might enter:
=== grog@freebie (/dev/ttyp4) ~ 14 -> cd docco/ === grog@freebie (/dev/ttyp4) "/docco 15 -> ls freebsd.faq freebsd.fbc freeware === grog@freebie (/dev/ttyp4) "/docco 16 -> emacs freebeepbsd.fbeepaq
Remember that my input is in constant width bold font, and the shell's output is in constant cd doc followed by a Tab character, and the shell completed with the text co/. On the last line, I entered the characters emacs f and a Tab. In this case, the shell determined that there was more than one file name that started like this, so it added the letters ree and rang the bell. I entered the letter b and pressed Tab again, and the shell added the letters sd.f and beeped again. Finally, aq to complete the file name freebsd.faq.
Command line completion in vi mode is similar: instead of pressing Tab, you press ESC twice.
As we saw above, there are a lot of ways to customize your shell. It would be inconvenient to have to set them every time, so all shells provide a means to set them automatically when you login. Nearly every shell has its own startup file. Table 7-6 gives an overview.
| Shell | startup file |
|---|---|
| bash | .profile, then .bashrc |
| csh | .login on login, always .cshrc |
| sh | .profile |
| tcsh | .login on login, always .tcshc, .cshrc if .tcshrc not found |
These files are shell scripts—in other words, straight shell commands. listing 7-1 shows a typical
.bashrc file to set the
umask 022 export BLOCKSIZE=1024 #for df export CVSROCT=/src/ncvs export EDITCR=/opt/bin/emacs export MANPATH=/usr/share/man:/usr/local/man export MCZILLA_HOME=/usr/local/netscape export PAGER=less export PATH=/usr/bin:/usr/local/bin:/usr/sbin:/bin:/sbin:/usr/X11R6/bin PS1="=== \u@\h rtty1) \w \# -> " PS2="\u@\h \w \! ++ " export SHELL=/usr/local/bin/bash export TAPE=/dev/nsa0 #note non-rewinding as standard if [ "$TERM" = "" ]; then export TERM=xterm fi if [ "$DISPLAY" = "" ]; then export DISPLAY=:0 fi /usr/games/fortune # print a fortune cookie
It would be tedious for every user to put settings in their private initialization files, so the shells also read a system-wide default file. For the Bourne shell family, it is /etc/profile, while the C shell family has three files: /etc/csh.login to be executed on login, /etc/csh.cshrc to be executed when a newshell is started after you login, and /etc/csh.logout to be executed when you stop a shell. The start files are executed before the corresponding individual files.
In addition, login classes (page 571) offer another method of setting
The FreeBSD installation gives root a C shell, csh.This is the traditional BSD shell, but it has a number of disadvantages: command line editing is very primitive, and the script language is significantly different from that of the Bourne shell, which is the de facto standard for shell scripts: if you stay with the C shell, you may still need to understand the Bourne shell. The latest version of the Bourne shell sh also includes some command line editing. See page 133 for details of how to enable it.
If you want to stay with a csh-like shell, you can get better command line editing with tcsh, which is also in the base system. You can get both better command line editing and Bourne shell syntax with bash, in the Ports Collection.
If you have root access, you can use vipw to change your shell, but there's a more general way: use chsh (ChangeShell). Simply run the program. It starts your favourite editor (as defined by the EDITOR
#Changing user database information for velte. Shell: /bin/csh Full Name: Jack Velte Location: Office Phone: Home Phone:
You can change anything after the colons. For example, you might change this to:
#Changing user database information for velte. Shell: /usr/local/bin/bash Full Name: Jack Velte Location: On the road Office Phone: +1-408-555-1999 Home Phone:
chsh checks and updates the password files when you save the modifications and exit the editor. The next time you login, you get the new shell. chsh tries to ensure you don't make any
bumble# su velte Password: su-2.00$ note the newprompt
You might hear objections to using bash as a root shell. The argument goes something like this: bash is installed in /usr/local/bin, so it's not available if you boot into single-user mode, where only the root file system is available. Even if you copy it to, say, /bin, you can't run it in single-user mode because it needs libraries in /usr/lib.
In fact, this isn't a problem. If you install the system the way I recommend in Chapter 5, /usr is on the root file system. Even if it isn't, though, you don't have to use bash in single-user mode. When you boot to single-user mode, you get a prompt asking you which shell to start, and suggesting /bin/sh.
If you're coming from a Microsoft background, there are a few got chas that you might trip over.
/ (slash) and \ (backslash) are confusing. As we've seen, UNIX uses / to delimit directories. The backslash \ is called an escape character. It has, several purposes:
Mail rejected to "Mail rejected" to stop the shell from interpreting it. We could also have written: Mail\ rejected.
A more common use for this quoting is to tell the shell to ignore the end of a line. If acommand line in a shell script gets too long, you might like to split it up into several lines; but the shell sees the end of a line as a go-ahead to perform the command. Stop it from doing so by putting a backslash immediately before the end of the line:
$ grep \ "Mail rejected" \ /var/log/maillog
Don't put any spaces between the \ and the end of the line; otherwise the shell will interpret the first space as a parameter by itself, and then it will interpret the end of line as the end of the command.
\n means "new line." This usage appears in many other places as well.\ as an escape character causes problems: how do we put a \ character on a line? The answer: quote it. Write \\ when you mean \. This causes particular problems when interfacing with Microsoft: if you give a Microsoft path name to a shell, it needs the doubled backslashes: C:\\WINDOWS.We've seen that the shell treats "white space," either spaces or tab characters, as the same. Unfortunately, some other programs do not. make, sendmail and syslogd make a distinction between the two kinds of characters, and they all require tabs (not spaces) in certain places. This is a real nuisance, because hardly any editor makes a distinction between them.
In the olden days, the standard computer terminal was a Teletype, a kind of computer-controlled electric type writer. When the carriage, which contained the print head, got to the end of a line, it required two mechanical operations to move to the beginning of the next line: the carriage return
Generations of computer systems emulated this \n.
This causes problems transferring data between FreeBSD and Microsoft, and also when printings to printers that still expect both characters. We'll look at the file transfer issues on page 260 and the printer issues on page 267.
A part from the shell, your second most important tool is the editor, a program that creates and changes texts. Another divergence of concept between UNIX and Microsoft environments is that UNIX gives you a choice of editors in just about anything you do. Microsoft products frequently try to redefine the whole environment, so if you change mailers, you may also have to change the editor you use to write mail. This has a profound effect on the way you work. In particular, the Microsoft way makes it uninteresting to write a really good editor, because you can't use it all the time.
The standard BSD editor is vi, about which people speak with a mixture of admiration, awe and horror. vi is one of the oldest parts of BSD. It is a very powerful editor, but nobody would say that it is easy to learn. There are two reasons to use vi:
If, on the other hand, you don't know vi, and you only work on systems whose software you can control, you probably shouldn't use vi. Emacs is much easier to learn, and it is more powerful than vi.
(рис 7.8) Emacs main menu
When running under X, Emacs displays its own window (v/' uses an xterm under these circumstances). As are sult, if you start Emacs from an xterm, you should use the character to start it in the background:
$ emacs
Figure 7-8 shows the resulting display. As you can see, the first thing that Emacs offers you is a tutorial. You should take it. You'll also notice the menu bars at the top. Although they look primitive compared to graphics toolbars, they offer all the functionality of graphics-oriented menus. In addition, they will tell you the keystrokes that you can use to invoke the same functions. Figure 7-9 gives an example of the Files menu.
There is a lot of documentation for Emacs, much of it on line. The complete Emacs
(рис 7.9) Emacs files menu
To stop X, press the key combination Ctrl-Alt-Backspace, which is deliberately chosen to resemble the key combination Ctrl-Alt-Delete used to reboot the machine. Ctrl-Alt-Backspace stops X and returns you to the
To stop the system, use the shutdown program. To do so, you need to be a member of group operator.
By default, KDE uses the halt program. Only root can use this program, so you should reconfigure KDE to use shutdown. After this, you can shut down from KDE with the
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