Question

I am making a bash script where I want to find files that are equal to a variable. The equals will then be used.

I want to use “mogrify” to shrink a couple of image files that have the same name as the ones i gather from a list (similar to “dpkg -l”). It is not “dpkg -l” I am using but it is similar. My problem is that it prints all the files not just the equals. I am pretty sure this could be done with awk instead of a for-loop but I do not know how.

prog="`dpkg -l | awk '{print $1}'`"

for file in $dirone* $dirtwo*
do
     if [ "basename ${file}" = "${prog}" ]; then
         echo ${file} are equal
     else
         echo ${file} are not equal
     fi
done

Could you please help me get this working?

Answer 1

First, I think there’s a small typo. if [ "basename ${file}" =... should have backticks inside the double quotes, just like the prog=... line at the top does.

Second, if $prog is a multi-line string (like dpkg -l) you can’t really compare a filename to the entire list. Instead you have to compare one item at a time to the filename.

Here’s an example using dpkg and /usr/bin

#!/bin/bash
progs="`dpkg -l | awk '{print $2}'`"

for file in /usr/bin/*
do
    base=`basename ${file}`

    for prog in ${progs}
    do
        if [ "${base}" = "${prog}" ]; then
            echo "${file}" matches "${prog}"
        fi
    done
done