5. Basic System Commands

5.1 Online Documentation

The man Command

Unix does not have an online help facility like VMS; instead, it has a man command which will display a section from the Unix manuals on your screen. Since each command has its own manual page(s), the effect is very similar to that of HELP on VMS - except that you must know the name of the command before you can ask for the manual page for it! Also, note that when you display the manual page you get the full documentation for the command; thus, you can learn all about the system without having access to printed documentation. On the other hand, this also means that there are no subtopics you can ask for individually - you get everything there is to know about the command.

For example:

man cd

will display documentation on the cd command,

man man

will display documentation on man itself.

The man command will display one screen full of text, and then pause with the following message appearing at the bottom of the screen:

        -- More --

At this point, you may type any of the following:

RETURN:

displays one more line and pauses again,

SPACE:

displays one more screen full and pauses again,

CTRL-C:

exits man and returns you to the command interpreter (shell),

CTRL-D:

moves forward half a screen full and pauses again.

SGI help

Silicon Graphics workstations running IRIX have a complete set of documentation on line. This can be found by selecting Help in the Toolchest and further selecting one of the items listed there.

5.2 Common VMS Commands and their Unix Equivalents

The following table shows some of the commands VMS users use frequently, together with the Unix equivalent. In all cases, full information about the Unix command can be obtained by using man. Boldface is used for actual Unix commands you type; normal typeface for parameters you must supply following the command. Some parameters are optional; these are enclosed in brackets. Numbers in parentheses after the Unix command refer to notes below:

VMS Command                             Unix equivalent
--- -------                             ---- ----------

COPY fromfile tofile                    cp fromfile tofile

CREATE/DIRECTORY directory              mkdir directory

DELETE file                             rm file

DELETE directory                        rmdir directory

DELETE [...]*.*;*                       rm -r directory         (1)
(Delete all files in a directory,
 including subdirectories and their
 files.)

DIRECTORY [directory or file]           ls [path]               (2)

DIRECTORY/FULL [directory or file]      ls -l [path]            (2)

PRINT filename                          lp filename             (3)

RENAME oldname newname                  mv oldname newname

RUN program                             program                 (4)

SET DEFAULT directory                   cd path

SHOW DEFAULT                            pwd

SET PASSWORD                            passwd

SET PROTECTION=protection file          chmod protection file   (5)

SET PROTECTION=protection/default       umask protection        (5)

SHOW PROTECTION                         umask                   (5)

SHOW USERS                              who

SHOW SYSTEM/SUBPROCESSES                ps                      (6)

TYPE file                               cat file

Notes on the above:

1. The Unix command also deletes the directory - not just all the subdirectories and files.

2. The Unix path may name either a directory or a file. If it is a directory, its contents are listed; if a file, just information on that file is listed. If no path is specified, the contents of the current default directory are listed.

3. There are two different printing systems in the Unix world. The version used by IRIX was originally supplied with the AT&T version of Unix uses the lp command to print files. The other system, supplied with Berkeley Unix systems (and used in Linux) uses the "lpr" command to print.

4. Note that almost all Unix commands do, in fact, run a program of the name specified by the command - e.g. ls runs the program /bin/ls; cat runs /bin/cat etc. The shell maintains a list of directories it searches to try to find a file with the name specified on the command line in order to run it. This list includes a number of system directories, plus the bin sub-directory of your home directory - which is where you should put all of your private executable programs to facilitate access to them regardless of what your current default directory is.

5. See the documentation for chmod for the format for specifying protections. Note that umask always shows a protection in numeric form, and requires you to specify it in this form as well. See the manual page for chmod for details, and note that there is no manual page for umask as a command (though there is one for the umask system service.) since it is built in to bash (the command interpreter), see the manual page for bash for more information.

6. By default, the ps command lists only sub-processes belonging to you; this can be overridden by command switches described on the manual page for ps.