shell - Checking for the correct number of arguments -

how check correct number of arguments (one argument). if tries invoke script without passing in correct number of arguments, , checking make sure command line argument exists , directory.

#!/bin/sh if [ "$#" -ne 1 ] || ! [ -d "$1" ];   echo "usage: $0 directory" >&2   exit 1 fi 

translation: if number of arguments not (numerically) equal 1 or first argument not directory, output usage stderr , exit failure status code.

more friendly error reporting:

#!/bin/sh if [ "$#" -ne 1 ];   echo "usage: $0 directory" >&2   exit 1 fi if ! [ -e "$1" ];   echo "$1 not found" >&2   exit 1 fi if ! [ -d "$1" ];   echo "$1 not directory" >&2   exit 1 fi