Note: Please look further down about help facilities specific to SDF, like the FAQ!
While the UNIX shell may seem a bit daunting and cold with cryptic two-letter commands, dozens of command line switches, and no animated paper clips to show you the way, there are several different ways of getting help from the system.
The easiest and most comprehensive way of getting help is reading the manpage. You've probably heard RTFM (Read The Fscking Manual) somewhere throughout your computer use, well, this is that Manual. Manpages are the standard form of documentation for every UNIX. Learn to use them. Learn to love them.
Where can you find them? It's pretty simple. Think of a command. (ls, rm, chmod, kill, grep) or a program (vi, mutt, snarf, majordomo) So go ahead, type
% man command
command being the name of the command you want to learn about. As you can see, manpages are broken down into sections. We'll use mkdir as an example.
% man mkdir
MKDIR(1) NetBSD General Commands Manual MKDIR(1) NAME mkdir - make directories SYNOPSIS mkdir [-p] [-m mode] directory_name ... DESCRIPTION mkdir creates the directories named as operands, in the order specified, using mode rwxrwxrwx (0777) as modified by the current umask(2). The options are as follows: -m Set the file permission bits of the final created directory to the specified mode. The mode argument can be in any of the for- mats specified to the chmod(1) utility. If a symbolic mode is specified, the operation characters ``+'' and ``-'' are inter- preted relative to an initial mode of ``a=rwx''. -p Create intermediate directories as required. If this option is not specified, the full path prefix of each operand must already exist. Intermediate directories are created with permission bits of rwxrwxrwx (0777) as modified by the current umask, plus write and search permission for the owner. Do not consider it an error if the argument directory already exists. The user must have write permission in the parent directory. EXIT STATUS mkdir exits 0 if successful, and >0 if an error occurred. SEE ALSO chmod(1), rmdir(1), mkdir(2), umask(2) STANDARDS The mkdir utility is expected to be IEEE Std 1003.2 (``POSIX.2'') compat- ible. NetBSD 2.0.2 January 25, 1994 NetBSD 2.0.2
mkdir command, the man page displayed has six
sections: NAME, SYNOPSIS, DESCRIPTION, EXIT STATUS, SEE ALSO, and
STANDARDS. The NAME section simply shows the name of the command and a
terse description of its function. The SYNOPSIS gives a brief
outline of the command syntax, so you can see what the command you
enter should look like. Items in square brackets [ ] are optional. The
DESCRIPTION section provides a detailed description of how the command
works, including information on the various options or modes of the
command. The EXIT STATUS section describes what status codes are
generated by the command when it completes (successfully
or unsuccessfully). These codes can be read by programs (such as a shell
script) to determine how to react to the command's result. SEE ALSO
provides cross referencing information for related commands or others
which may be helpful. And finally, the STANDARDS section lists
information on which standards this particular command complies with.
The manual is divided up into nine sections:
In some cases, the same topic will appear on more than one section of the manual. For example, there is a chmod user command and a chmod() system call. How would you find the appropriate manpage? You can tell man which section you'd like to look under. If you wanted to find the user command you would type:
% man 1 chmod
This would display the manpage for the user command chmod. References to the specific sections are traditionally placed in parenthesis after the command name like so: chmod(1)
Well, this is all fine and good if you know the name of the command, but what if you can't remember the name? 'man -k' can be used to search for keywords in the command descriptions. So, if you want to find a mail program you would type:
% man -k editor
A list of commands with the keyword "editor" in their descriptions will be presented on the screen.
For programs of the GNU Project, you may
also use the
info command. If you know the name of a program,
give it as an argument (like with
In fact, you can use
info as an alias to
because the info reader will simply display the man page if it cannot find an
info entry (but you cannot specify the manpage section).
However, navigation is different in the standard info reader, as it is
based on the
emacs text editor.
Quick key help (for more, consult
There are also a number of tools at SDF that you can use to get more help. Type the following commands at a shell prompt.