Parameters Set by the Shell

Bash shell set several special parameters. For example $? (see return values section) holds the return value of the executed command.

• All command line parameters or arguments can be accessed via $1, $2, $3,..., $9.
• $* holds all command line parameters or arguments.
• $# holds the number of positional parameters.
• $- holds flags supplied to the shell.
• $? holds the return value set by the previously executed command.
• $$ holds the process number of the shell (current shell).
• $! hold the process number of the last background command.
• $@ holds all command line parameters or arguments.

Use echo command to display special shell parameters:

echo $#

You can store them to a shell variables as follows:

status=$?
[ $status -eq 0 ] && echo "Lighttpd ... [Ok]" || echo "Lighttpd ... [Failed]"

• Assignment to special parameter is not allowed:

# okay
status=$?
# noop not allowed
$?=-1