Reputation: 1667
I know how to give default values to arguments in bash or exit with an error message if one is unset. (from here)
I want to make check if an argument was set, execute some code if it wasn't and the exit.
if [$1 is not set]; then
execute command
fi
I am writing a wrapper around another command. It has it's own usage message if no first argument is set (it is actually an input filename). It has other inputs that I am hardcoding for now. The actual command in the bash script is something like :
command $1 12 3124 534
I want to invoke it's own help message if no $1 was sent to the script.
Upvotes: 0
Views: 141
Reputation: 77197
Just check the length of arguments:
if (( $# < 1 )); then
echo 'There are no arguments, so you can bet that $1 was not set.'
fi
It's usually trivial to check if a variable has a non-empty value in shell:
[ -n "$val" ]
However, if you want to determine if a name has been declared I'll refer you to BashFAQ 83
Upvotes: 4