CODEWITHSUNDEEP
shellargumentsflags
user1508893
user1508893

Reputation: 9793

script with simple flag

Suppose I have this simple script

#! /bin/sh

if [ $# -ne 2 ]
then
        echo "Usage: $0 arg1 arg2"
        exit 1
fi

head $1 $2

## But this is supposed to be:
## if -f flag is set, 
##      call [tail $1 $2]
## else if the flag is not set
##      call [head $1 $2]

So what's the simplest way to add a 'flag' checking to my script?

Thanks

Upvotes: 0

Views: 218

Answers (2)

sti
sti

Reputation: 11075

I usually go for the "case" statement when parsing options:

case "$1" in
    -f) call=tail ; shift ;;
    *)  call=head ;;
esac

$call "$1" "$2"

Remember to quote the positional parameters. They might contain file names or directory names with spaces.

If you can use e.g. bash instead of Bourne shell, you can use e.g. the getopts built-in command. For more information see the bash man page.

Upvotes: 1

Jo So
Jo So

Reputation: 26501

fflag=no
for arg in "$@"
do
    test "$arg" = -f && fflag=yes
done

if test "$fflag" = yes
then
    tail "$1" "$2"
else
    head "$1" "$2"
fi

This simpler approach might also be viable:

prog=head
for i in "$@"
do
    test "$i" = -f && prog=tail
done

$prog "$1" "$2"

Upvotes: 1

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