Bash, no-arguments warning, and case decisions

Question

Hi,

I am learning bash.

I would like to do a simple script that, when not arguments given, shows some message. And when I give numers as argument,s depending on the value, it does one thing or another.

I would also like to know suggestions for the best online manuals for beginners in bash

Thanks

Answer 1

if [ $# -eq 0 ] ; then
    echo 'some message'
    exit 0
fi

case "$1" in
    1) echo 'you gave 1' ;;
    *) echo 'you gave something else' ;;
esac

The Advanced Bash-Scripting Guide is pretty good. In spite of its name, it does treat the basics.

Answer 2

Example

 if [ -z "$*" ]; then echo "No args"; fi

Result

No args

Details

-z is the unary operator for length of string is zero. $* is all arguments. The quotes are for safety and encapsulating multiple arguments if present.

Use man bash and search (/ key) for "unary" for more operators like this.

Answer 3

you might also want to look at getopts