C Shell maintains a set of variables that can be assigned
values by the set
command. Shell variables are useful for storing values for later
use in commands. The most commonly referenced shell variables are,
however, those which the shell itself refers to. By changing the
values of these variables, you can directly affect the shell behavior.
The following variables are supported by C Shell on HP-UX.
argv |
 |
This variable contains the command line arguments from the
calling shell.
autologout |
|
This variable is used to automatically log you off the system
if you do not use the system for a specified amount of time. For
example,
will automatically log you off the system if you do not use
the system for an hour (60 minutes).
To disable autologout, set it to zero (0) time. For example:
or
cwd |
|
The cwd
variable contains the path name to your current working directory.
This variable is automatically changed with each cd
(Change Directory) command. At logon, the default for this variable
is the directory in the system variable HOME.
home |
|
The home
variable contains the path name to your home directory. The default
value for this variable is specified in the system file /etc/passwd.
(See passwd(5).)
Boolean ignoreeof |
|
The boolean variable ignoreeof
determines whether CTRL-D
is allowed to log you off the system. If set,
logout must be used to terminate
a session. If ignoreeof
is unset,
you can also use CTRL-D
to log off. The default is set.
cdpath |
|
Use this variable to specify alternate directories to be searched
by the system when locating subdirectory arguments used with pushd,
cd, and chdir
commands.
Boolean noclobber |
|
Suppose you use the following command sequence to send keyboard
input to a file called newfile.
If newfile
exists before this command sequence is executed, the old copy of
newfile will
be overwritten and thus destroyed. To prevent accidental overwriting
of a file containing valuable information, set the boolean noclobber
variable so that C Shell cannot overwrite files by including the
command line:
in your .login file. To demonstrate its
effectiveness, type the following C Shell commands:
% cat > newfile
This is a test message.
EOT
%set noclobber
cat > newfile
newfile: File Exists.
% |
When you try to cat
to an existing file with noclobber
set, the system tells you the File Exists
and aborts the command. To override the noclobber,
use the exclamation point metacharacter. For example:
%cat > newfile
newfile: File Exists.
%cat >! newfile
This is an override test.
EOT
% |
Boolean notify |
|
If the notify variable is
set, you are immediately notified when a background process finishes.
If unset, notification
messages related to background process completion occur with the
next presentation of the C Shell prompt. Use the set
command to set notify.
path |
|
The path variable is one
of the most important variables in C Shell operation. This variable
contains a sequence of directory names C Shell searches for commands.
For example:
set path=(/bin/posix /bin /usr/bin /usr/local/bin /usr/bin /etc .) |
or
setenv PATH /bin/posix:/bin:/usr/bin:/usr/local/bin:/etc:. |
PATH is a system variable,
and path is a
C Shell variable that serves the same purpose. The first is global,
while the second is local to the running shell.
When C Shell is first executed, a hash table of command locations
is created. This table is created by looking through the directories
specified in PATH (except for the
current working directory) in the order specified by PATH.
Suppose you were to write one or more new commands and store them
in one of the directories in your path other than your current working
directory. The system has no way of knowing they are there until
you notify it of their presence by using the rehash
command. The hash table never gets built from commands in .,
your current working directory, so new commands put into .
don't affect the hash table. But, if your path contained $HOME/tools/bin
and you put a new command in there, then rehash
would add it to hash table. The hash table also gets rebuilt whenever
your PATH is changed.
prompt |
|
This variable is used to customize your C Shell prompt. For
example,
% set prompt = "[\!] % "
[22] % _ |
sets the prompt to indicate the command (event) number of
the current command. This is very useful when using the History
mechanism.
shell |
|
Some HP-UX commands, such as mailx
and vi, spawn
a new shell when they begin execution, while others may spawn one
or more new shells during normal operation. If the program or command
is written so that it recognizes the shell
variable, you can set the variable to define the type of shell to
be spawned by the program. For example:
selects C Shell, while
set shell = /bin/posix/sh |
selects POSIX Shell.
This technique is valid only if the command or program recognizes
that uses the variable when spawning new shells. Be careful when
using the shell variable. The result
may or may not be what you intended.
status |
|
This variable returns 0 if the most recently executed command
was completed without error. A nonzero value means an error was
detected.
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