gno/doc/refs/gsh/commands.sgml
gdr-ftp 5eed4a4a87 gsh user's manual:
- initial checkin.  Only minor changes from the v2.0.4 version.
	  It still needs to be reviewed as to currency.
1999-02-21 18:46:51 +00:00

1196 lines
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<!--
;; $Id: commands.sgml,v 1.1 1999/02/21 18:46:50 gdr-ftp Exp $
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<chapter id="gsh-commands">
<title>Builtin Command Reference</title>
<sect1>
<title>Builtin vs External Commands</title>
<para>
The term "built-ins" is used to
describe commands that exist within the shell itself. These
utilities run faster than external commands because the code is
already loaded into memory. Files of type "EXE", on the
other hand, must be loaded into memory by gsh and
executed. If an EXE command is executed again, it might, again,
have to be loaded into memory. This results in longer execution
time for the program.
</para>
<para>
gsh has a number of built-in commands which allow you to work with the
shell, the GNO kernel, and the shell environment.
</para>
<para>
The following section describes the
commands that are built-in to gsh. The "[..]"
character sequence represents an optional argument to a command.
The term "SIGNAL" is used to represent one of the signal names
or numbers listed in Appendix D Signals. The sequence
"..." means the command accepts multiple arguments of
the same type as the argument before the "..."
sequence. The sequence "{..}" is used to represent a
set, which is a list of possible arguments to choose from.
</para>
</sect1>
<sect1 id="gsh-commands-builtin">
<title>Builtin Shell Commands</title>
<variablelist>
<varlistentry>
<term>
bindkey [-l]
<replaceable>function</replaceable> <replaceable>string</replaceable>
</term>
<listitem>
<para>
Bindkey is used to customize the shell's
command-line editor. Any key on the keyboard can be mapped to any
of a number of functions. The various functions are as follows:
</para>
<para>
<table colsep="1" frame="all" rowsep="1" tocentry="1" shortentry="0"
orient="land" pgwide="0">
<title>bindkey Functions</title>
<tgroup cols="2">
<colspec align="left">
<thead>
<row>
<entry align="center">Function</entry>
<entry align="center">Meaning</entry>
</row>
</thead>
<tbody>
<row>
<entry>
backward-char
</entry>
<entry>
move cursor left
</entry>
</row>
<row>
<entry>
backward-delete-char
</entry>
<entry>
delete character to the left
</entry>
</row>
<row>
<entry>
backward-word
</entry>
<entry>
move cursor left one word
</entry>
</row>
<row>
<entry>
beginning-of-line
</entry>
<entry>
move cursor to beginning of line
</entry>
</row>
<row>
<entry>
clear-screen
</entry>
<entry>
clear screen and redraw prompt
</entry>
</row>
<row>
<entry>
complete-word
</entry>
<entry>
perform filename completion
</entry>
</row>
<row>
<entry>
delete-char
</entry>
<entry>
delete character under cursor
</entry>
</row>
<row>
<entry>
down-history
</entry>
<entry>
replace command line with next history
</entry>
</row>
<row>
<entry>
end-of-line
</entry>
<entry>
move cursor to end of line
</entry>
</row>
<row>
<entry>
forward-char
</entry>
<entry>
move cursor to the right
</entry>
</row>
<row>
<entry>
forward-word
</entry>
<entry>
mvoe cursor one word to the right
</entry>
</row>
<row>
<entry>
kill-end-of-line
</entry>
<entry>
delete line from the cursor to end of line
</entry>
</row>
<row>
<entry>
kill-whole-line
</entry>
<entry>
delete the entire command line
</entry>
</row>
<row>
<entry>
list-choices
</entry>
<entry>
list file completion matches
</entry>
</row>
<row>
<entry>
newline
</entry>
<entry>
finished editing, accept command line
</entry>
</row>
<row>
<entry>
raw-char
</entry>
<entry>
character as-is
</entry>
</row>
<row>
<entry>
redisplay
</entry>
<entry>
redisplay the command line
</entry>
</row>
<row>
<entry>
toggle-cursor
</entry>
<entry>
toggle between insert and overwrite cursor
</entry>
</row>
<row>
<entry>
undefined-char
</entry>
<entry>
this key does nothing
</entry>
</row>
<row>
<entry>
up-history
</entry>
<entry>
replace command line with previous history
</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
<para>
Keys are bound to functions, not
vice-versa. This means that you can have any number of commands
refer to the same function. For example, the default bindings
have <userinput>CTRL-A</userinput> and <userinput>OA-&lt;</userinput>
both bound to <userinput>beginning-of-line</userinput>.
</para>
<para>
Most of the function names are
self-explanatory, and are explained in Chapter 2, but a few
deserve discussion.
<userinput>raw-char</userinput>
is what you should bind a key that should be
inserted into the command-line as-is. The regular printable ASCII
set, such as the letters a-z, numbers, etc. are bound to
<userinput>raw-char</userinput>.
Control characters should not be bound to
<userinput>raw-char</userinput>
because the command-line editor will become confused (most control characters
act as special GNO/ME console feature codes - see the
<ulink url="http://www.gno.org/~gno/kern.html">GNO Kernel Reference
Manual</ulink>).
</para>
<para>
Any keystroke that should be rejected by
the editor should be bound to
<userinput>undefined-char</userinput>.
By default, this includes control characters and OA-sequences that
are not assigned to any editing features. Any key bound to
<userinput>undefined-char</userinput>
will cause gsh to beep and ignore the key.
</para>
<para>
You can actually bind key sequences, not
just keystrokes, to functions. There is no limit other than
memory to how many characters are in a command sequence.
</para>
<para>
Because terminals do not have the OA (Open Apple) key, OA is actually
mapped by the kernel to a two-character sequence consisting of
<userinput>ESC</userinput>
and the key. For example, OA-Y would actually produce
<userinput>ESC-Y</userinput>.
</para>
<para>
Control characters in the
<replaceable>string</replaceable>
are represented in ^X format; e.g. CTRL-A is represented by ^A.
ESC (and OA) is represented by ^[.
</para>
<informalexample id="ex-bindkey">
<screen id="sc-bindkey">
<prompt>gno% </prompt> <userinput>bindkey kill-end-of-line ^K</userinput>
map Ctrl-K to kill-end-of-line (like Emacs)
<prompt>gno% </prompt> <userinput>bindkey clear-screen ^[^X</userinput>
map OA-Clear to clear-screen
</screen>
</informalexample>
</listitem>
</varlistentry>
<varlistentry>
<term>
commands
</term>
<listitem>
<para>
Displays a list of all built-in shell commands.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
cd [<replaceable>pathname</replaceable>]
</term>
<term>
chdir [<replaceable>pathname</replaceable>]
</term>
<listitem>
<para>
Changes the current working directory to
<replaceable>pathname</replaceable>.
If <replaceable>pathname</replaceable>
is not given, the default home directory (i.e. the value of the HOME
environment variable) is used. This makes it easy
to move back to your home directory. Under gsh, unlike
most UNIX shells, the cd is not necessary, except to change
automatically to your HOME directory. If the first word on the command line
is neither a builtin nor an external command, but is instead the name of
a directory, a cd is implied and performed on the directory unless the
NODIREXEC variable has been set.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
clear
</term>
<listitem>
<para>
This command takes no arguments. When invoked, the screen will be cleared.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
dirs
</term>
<listitem>
<para>
See <userinput>pushd</userinput>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
echo [-n] [<replaceable>arg</replaceable> ...]
</term>
<listitem>
<para>
Expands the "<replaceable>arg</replaceable>"
expression(s) and outputs them to the screen. If the -n flag is specified,
a newline character is <emphasis>not</emphasis> output after the last
<replaceable>arg</replaceable> expression.
Special escape sequences may also be included in the
arguments, similar to those used in C strings:
</para>
<INFORMALTABLE COLSEP="1" FRAME="all" ROWSEP="1"
SHORTENTRY="0" TOCENTRY="0" ORIENT="land" PGWIDE="0">
<TGROUP COLS="2">
<COLSPEC ALIGN="left">
<TBODY>
<ROW>
<ENTRY>\b</ENTRY>
<ENTRY>backspace</ENTRY>
</ROW>
<ROW>
<ENTRY>\f</ENTRY>
<ENTRY>form feed (clears screen)</ENTRY>
</ROW>
<ROW>
<ENTRY>\n</ENTRY>
<ENTRY>newline</ENTRY>
</ROW>
<ROW>
<ENTRY>\r</ENTRY>
<ENTRY>carridge return</ENTRY>
</ROW>
<ROW>
<ENTRY>\t</ENTRY>
<ENTRY>tab</ENTRY>
</ROW>
<ROW>
<ENTRY>\<replaceable>nnn</replaceable></ENTRY>
<ENTRY>a decimal ASCII code</ENTRY>
</ROW>
</TBODY>
</TGROUP>
</INFORMALTABLE>
</listitem>
</varlistentry>
<varlistentry>
<term>
exit
</term>
<listitem>
<para>
Exits the shell or terminates a shell script.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
history
</term>
<listitem>
<para>
This command displays the list of previous
command-line entries. The number of entries saved is set in the
HISTORY variable.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
pushd [<replaceable>newdir</replaceable> | +<replaceable>n</replaceable>]
</term>
<term>
popd [+<replaceable>n</replaceable>]
</term>
<term>
dirs
</term>
<listitem>
<para>
These three commands maintain the shell's directory stack.
Let's say you're working in a directory
/src/myprogs/class/program.1/,
and you want to temporarily go to another directory. Instead of having to
<userinput>cd</userinput>
there and
<userinput>cd</userinput>
back to a very long directory name (i.e., lots of typing), you can use
the pushd command, like so:
</para>
<screen id="sc-pushd">
<prompt>gno% </prompt> <userinput>pwd</userinput>
/src/myprogs/class/program.1
<prompt>gno% </prompt> <userinput>pushd /etc</userinput>
<prompt>gno% </prompt> <userinput>pwd</userinput>
/etc
<prompt>gno% </prompt> <userinput>popd</userinput>
<prompt>gno% </prompt> <userinput>pwd</userinput>
/src/myprogs/class/program.1
</screen>
<para>
The
<userinput>pushd</userinput>
command stores the current directory on a stack,
and then changes the current directory to the argument
<replaceable>newdir</replaceable>.
When you want to go back to the original directory, type popd. The shell
will pull the last directory off the stack and make that directory
the current directory.
If no argument is given, then the current directory is swapped with the
directory that is currently on the top of the directory stack.
If a digit argument, +<replaceable>n</replaceable>, is given, then
the current directory will be swapped with the directory in the
<replaceable>n</replaceable>th position on the directory stack.
</para>
<para>
The <userinput>popd</userinput>
command, when given without an argument, will pop the directory that
is on top of the directory stack, and make that directory the current
directory. When given an argument of +<replaceable>n</replaceable>,
<userinput>popd</userinput>
will remove the
<replaceable>n</replaceable>th
directory from the stack. It does not change
to that directory.
</para>
<para>
The <userinput>dirs</userinput>
command displays the current directory stack.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
pwd
</term>
<listitem>
<para>
Displays the current working directory.
This is useful if you have not configured the PROMPT string
to print your current working directory.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
source
</term>
<listitem>
<para>
When a script is executed, gsh
creates a new process to run the script. As a result, scripts
cannot change the parent shell's environment.
Instead of executing the script directly, you may use the
<userinput>source</userinput>
command which does not create a new process to execute the script. Thus, the
<userinput>source</userinput>
command is effectively exactly like typing all the
commands in the script from the keyboard.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
tset
</term>
<listitem>
<para>
The
<userinput>tset</userinput>
command causes the shell to reread the /etc/termcap
file and reset its output system to use the terminal type
specified in the TERM environment variable. On startup, after reading the
gshrc file, gsh
automatically does a
<userinput>tset</userinput>.
gsh also automatically does a tset whenever
the TERM variable is changed with the
<userinput>set</userinput>
command. You would
use tset manually if, for example, a utility changed the value of
TERM.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
which <replaceable>command</replaceable> [...]
</term>
<listitem>
<para>
Let's say that you are working on a new
version of the venerable shell utility
<userinput>ls</userinput>.
Since a search of the hash table is done before searching the current
directory, you might accidentally be using the wrong version of the command.
You make changes and run the new program, but your changes don't
seem to appear! Use the
<userinput>which</userinput>
command to check your sanity. Which also comes in
handy in locating duplicate program names in the PATH
directories (for example, an
<userinput>ls</userinput>
in both /bin and /usr/bin.)
</para>
<para>
The way to access a utility in the current
directory which has the same name as a program in the PATH is to
prefix the command name with
'<userinput>.</userinput>', as in
'<userinput>./ls</userinput>'.
See also
<userinput>rehash</userinput> and
<userinput>unhash</userinput>.
</para>
</listitem>
</varlistentry>
</variablelist>
</sect1>
<sect1 id="gsh-commands-kern">
<title>Kernel Commands</title>
<para>
gsh provides a set of commands to control the GNO kernel. These commands
mainly deal with job control. See the chapter on
<emphasis>Process Management</emphasis> in the
<ulink url="http://www.gno.org/~gno/kern.html">GNO Kernel Reference
Manual</ulink>.
</para>
<variablelist>
<varlistentry>
<term>
bg (%<replaceable>job</replaceable> | <replaceable>pid</replaceable>)
</term>
<listitem>
<para>
Starts the specified job, if stopped, and places it in the background.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
fg (%<replaceable>job</replaceable> | <replaceable>pid</replaceable>)
</term>
<listitem>
<para>
Starts the specified job, if stopped, and places it in the foreground.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
jobs [-l]
</term>
<listitem>
<para>
Displays a list of the shell's jobs. If the <command>-l</command>
switch is specified, the process id is
included in the job list.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
kill {[-<replaceable>SIGNAL</replaceable>] | %<replaceable>job</replaceable> | <replaceable>pid</replaceable> | [-l] }
</term>
<listitem>
<para>
The kill command will send the signal <replaceable>SIGNAL</replaceable>
to the process number <replaceable>pid</replaceable>.
The <command>ps</command> command documented below describes how
to list all process ID's currently executing.
</para>
<para>
<replaceable>SIGNAL</replaceable>
can be either a numeric value or string representing the signal
to be sent to the process. All signals are documented in
the chapter on <emphasis>Interprocess Communication</emphasis> in the
<ulink url="http://www.gno.org/~gno/kern.html">GNO Kernel Reference
Manual</ulink>.
Alternatively, specifying the <command>-l</command> option will list all
the signals and their names.
</para>
<para>
If the process number isn't known, but the
job number is, replace the pid with a '%' followed by the job
number.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
ps
</term>
<listitem>
<para>
This command takes no arguments. When
invoked, a list of all currently running processes is displayed:
</para>
<screen>
[2] 9:52pm root&gt; <command>ls -lR :hard:gno &gt; /ram5/dev &amp;</command>
[1] + 35 Running ls -lR :hard:gno &amp;
[3] 9:53pm root&gt; <command>ps</command>
ID STATE TT MMID UID TIME COMMAND
1 ready co 1002 0000 0:26 NullProcess
2 ready co 1005 0000 0:02 gsh
35 ready co 100A 0000 0:01 ls -lR :hard:gno
36 running co 1007 0000 0:00 ps
[4] 9:53pm root&gt;
[1] + Done ls -lR :hard:gno
</screen>
<para>
The fields of the <command>ps</command> output are as shown below:
</para>
<!-- starting nested list level 2 -->
<variablelist>
<varlistentry>
<term>
ID
</term>
<listitem>
<para>
A unique process ID assigned to a command by GNO. Use this number
to reference any process.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
STATE
</term>
<listitem>
<para>
Current state of the process. Each process can be in any of the
following states:
</para>
<!-- starting nested list level 3 -->
<variablelist>
<varlistentry>
<term>
RUNNING
</term>
<listitem>
<para>
The process is currently in execution.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
READY
</term>
<listitem>
<para>
The process is not currently executing, but is ready to be
executed as soon as it is assigned a time slice.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
BLOCKED
</term>
<listitem>
<para>
The process is waiting for a slow I/O operation to
complete (for instance, a read from a TTY).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
NEW
</term>
<listitem>
<para>
The process has been created, but has not executed yet.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
SUSPENDED
</term>
<listitem>
<para>
The process was stopped with SIGSTOP, SIGTSTP, SIGTTIN, or SIGTTOU.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
WAITING
</term>
<listitem>
<para>
The process is waiting on a semaphore "signal" operation.
Programs waiting for data from a pipe have this state.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
WAITSIGCH
</term>
<listitem>
<para>
The process is waiting to receive a SIGCHLD signal.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
PAUSED
</term>
<listitem>
<para>
The process is waiting for any signal.
</para>
</listitem>
</varlistentry>
</variablelist>
<!-- done nested list level 3 -->
</listitem>
</varlistentry>
<varlistentry>
<term>
TTY
</term>
<listitem>
<para>
Terminal connected to the process.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
MMID
</term>
<listitem>
<para>
Memory Manager ID assigned to the process.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
UID
</term>
<listitem>
<para>
ID of the user who initiated the process.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
TIME
</term>
<listitem>
<para>
How much CPU time this process has used. This is not the elapsed
time of the process.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
COMMAND
</term>
<listitem>
<para>
Command-line string used to invoke process.
</para>
</listitem>
</varlistentry>
</variablelist>
<!-- done nested list level 2 -->
</listitem>
</varlistentry>
<varlistentry>
<term>
setdebug { <replaceable>val</replaceable> | {+|-}<replaceable>flag</replaceable> }
</term>
<listitem>
<para>
Turns GNO kernel debugging code on or off.
The value passed consists of a bit field, where each bit
specifies a different type of debugging code to activate. An
alternate method is to provide a list of debug flags, either
preceded by a '+' or a '-'. Those preceded by a '+' are
activated, and those preceeded with a '-' are deactivated. All
debugging is deactivated by passing a value of 0. Running
setdebug wtth no arguments returns a list of the debugging flags.
Legal flags include:
</para>
<!-- tribby: could you verify which calls gsh is making to the
kernel, and verify that the debug values listed in <gno/gno.h> are
in fact correct? That has not yet been checked. -->
<para>
<table colsep="1" frame="all" rowsep="1" tocentry="1" shortentry="0"
orient="land" pgwide="0">
<title>Kernel Debug Flags</title>
<tgroup cols="2">
<colspec align="left">
<thead>
<row>
<entry align="center">Flag</entry>
<entry align="center">Meaning</entry>
</row>
</thead>
<tbody>
<row>
<entry>
gsostrace
</entry>
<entry>
Trace GS/OS calls.
</entry>
</row>
<row>
<entry>
gsosblocks
</entry>
<entry>
Trace GS/OS parameter blocks.
</entry>
</row>
<row>
<entry>
gsoserrors
</entry>
<entry>
Trace GS/OS errors.
</entry>
</row>
<row>
<entry>
pathtrace
</entry>
<entry>
Trace GS/OS pathnames.
</entry>
</row>
<row>
<entry>
sigtrace
</entry>
<entry>
Trace signals.
</entry>
</row>
<row>
<entry>
systrace
</entry>
<entry>
Trace GNO Kernel system calls.
</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
stop { %<replaceable>job</replaceable> | <replaceable>pid</replaceable> }
</term>
<listitem>
<para>
Stops the execution of all processes in a specified job.
</para>
</listitem>
</varlistentry>
</variablelist>
<!-- done nested list level 1 -->
</sect1>
<sect1 id="gsh-commands-environ">
<title>Environment Commands</title>
<para>The last set of commands, environment
commands, modify the <command>gsh</command> environment. Many of these
commands have been used in other parts of this manual and,
therefore, should not be new.
</para>
<variablelist>
<varlistentry>
<term>
alias [<replaceable>name</replaceable>] [<replaceable>value</replaceable>]
</term>
<listitem>
<para>
Creates an alias for a string. When this
alias is referenced as a command, <replaceable>value</replaceable>
will be expanded
into the command line. For commands that require many arguments
or have several steps, you could set up an alias to save typing.
You can also use aliases to create new names for commands. To
obtain a list of all aliases, invoke <command>alias</command>
with no arguments.
To list the value of a specific alias, invoke <command>alias</command>
with <replaceable>name</replaceable> only.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
export [<replaceable>variable</replaceable> ...]
</term>
<listitem>
<para>
When a shell environment variable is marked
as exportable, any process that is created from within the
current process (most likely <command>gsh</command>), will be passed copies
of the exported variables.
See <command>setenv</command> and
<xref linkend="gsh-shellvars-scope">.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
hash
</term>
<listitem>
<para>
Displays a list of all commands currently
in the shell's hash table; i.e., a list of commands in the
various $PATH directories.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
prefix [<replaceable>prefixnum</replaceable>
[<replaceable>prefixname</replaceable>]]
</term>
<listitem>
<para>
GNO maintains a list of 32 'prefixes' for
each process. Prefixes allow the user to reference a directory
with a number. While <command>gsh</command> provides this ability with
environment variables, the prefix command exists to support the
ORCA compilers and other utilities that are dependent on certain
GS/OS prefixes.
<xref linkend="gsh-app-prefix"> contains a list of these prefixes and
their "default" meanings, as documented in the
"Apple IIgs GS/OS Reference".
</para>
<para>
If <replaceable>refixname</replaceable> is not given, then the value of
<replaceable>prefixnum</replaceable> is displayed.
If neither argument is given, a list of currently assigned
prefixes is displayed.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
rehash
</term>
<listitem>
<para>
To decrease the time spent searching for a
command, <command>gsh</command> builds a hash table of all commands which were
found in the pathnames set in the $PATH environment variable. When a
command is invoked, only this list is searched. When the $PATH environment
variable is changed, <command>gsh</command> must rebuild this list. The
<command>rehash</command> command tells <command>gsh</command> to rebuild
the list.
</para>
<para>
While the old list is still active, if $PATH is
changed and one of the previous search paths is no longer online,
<command>gsh</command> will try and execute the command from the offline
device, resulting in a command failure.
</para>
<!-- tribby: that last bit is perhaps misleading. It sounds like only
the directories are hashed, not the actual commands. I suspect that
it is really the commands - gdr -->
</listitem>
</varlistentry>
<varlistentry>
<term>
set [<replaceable>var</replaceable> [<replaceable>value</replaceable>]] [...]
</term>
<term>
set <replaceable>value</replaceable>=<replaceable>value</replaceable> [...]
</term>
<term>
setenv [<replaceable>var</replaceable> <replaceable>value</replaceable>] [...]
</term>
<listitem>
<para>
Use these command to create or modify environment variables. If
<command>set</command> is invoked with no arguments, a list of the current
environment variables is displayed. If only <replaceable>var</replaceable>
is given as an argument, the value of <replaceable>var</replaceable>
is displayed. To set or reset a variable, use both the
<replaceable>var</replaceable> and <replaceable>value</replaceable>
arguments. There are two ways to set a variable, either by
"<replaceable>var</replaceable> <replaceable>value</replaceable>", or by
"<replaceable>var</replaceable>=<replaceable>value</replaceable>".
To set multiple variables at once, simply
list them all on the command line as shown above.
</para>
<para>
<command>setenv</command> works just like <command>set</command>,
but automatically exports the variable(s) or lists
only exported variables.
</para>
<para>
When using <command>set</command> or <command>setenv</command> to view
a list of variables, exported variable names appear in all capital letters.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
unalias <replaceable>name</replaceable> [...]
</term>
<listitem>
<para>
To remove an alias from the alias list, use
this command. To remove multiple aliases with one command,
specify all the aliases on the command line.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
unhash
</term>
<listitem>
<para>
To disable the internal hash table created
with the <command>rehash</command>
command, use this command. This is useful if you
wish to use only utilities in the current working directory
(during testing, for example).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
unset <replaceable>var</replaceable> [...]
</term>
<listitem>
<para>
To remove a variable from the environment, use <command>unset</command>.
<command>unset</command> accepts multiple names if more than one variable is
to be deleted. Future attempts to access the variable
<replaceable>var</replaceable> will result
in an error or a NULL string, depending on the circumstances.
</para>
</listitem>
</varlistentry>
</variablelist>
</sect1>
</chapter>