Question

I need a good reference on unix shell special variables (csh, ksh and bash).

e.g. $1, $*, $#, etc.

Answer 1

Here: http://sillydog.org/unix/scrpt/scrpt2.2.2.php

$1 – $9 these variables are the
positional parameters.

$0 the name of the command
currently being executed.

$# the number of positional
arguments given to this
invocation of the shell.

$? the exit status of the
last command executed is
given as a decimal string. When a command
completes successfully, it returns the exit status
of 0 (zero), otherwise it returns a non-zero exit
status.

$$ the process number of
this shell – useful for
including in filenames, to make them unique.

$! the process id of the
last command run in
the background.

$- the current options
supplied to this invocation
of the shell.

$* a string containing all
the arguments to the
shell, starting at $1.

$@ same as above, except
when quoted.

More resources :

• http://linuxshellaccount.blogspot.com/2008/04/shell-special-variables-in-bash.html
• http://www.tutorialspoint.com/unix/unix-special-variables.htm