Ngtjyty

I want to delete multiple images having resolution less then 228x228.
For that, I wrote this shell script:

#!/bin/bash



for i in $( ls ); do

    if [$(identify -format "%w" $i) < 228] && [$(identify -format "%h" $i) < 228];

    then

        rm $i

    fi

done

For some reasons, I got this output when I run it:

./del.sh: line 4: [640: command not found

./del.sh: line 4: [550: command not found

./del.sh: line 4: [315: command not found

...

Could you please tell me what's wrong in this script and how to fix it.

Thank you.

Some issues here: Firstly, the expression in a […] test needs spaces around it (pitfall #10), and secondly
the comparison < doesn't work with […] tests (pitfall #7). You either need -lt (less than)
or use [[…]] instead, which is a bashism. Also, the for loop should be replaced (pitfall #1).

So:

for i in ./*; do

    if [ -e "$i" ]; then

        if [ $(identify -format "%w" "$i") -lt 228 ] && [ $(identify -format "%h" "$i") -lt 228 ];

        then

            rm -- "$i"

        fi

    fi

done

You may also want to avoid calling identify twice to get the two dimensions (pitfall #58) but call
it just once instead and let it print a string ready to be used as variable assignments in shell syntax.

If we write

identify -format "width=%w height=%h" "$i"

it will print something like width=50 heigth=250. When we evaluate that string then we have set two variables with just one call and the condition can be written as:

eval "$(identify -format "width=%w height=%h" "$i")"

if [ $width -lt 228 ] && [ $height -lt 228 ];

then

    rm -- "$i"

fi

See also: common bash pitfalls.

Instead of a loop, I'd use find with -exec and -delete:

find . -maxdepth 1 -type f  

   -exec sh -c '

       [ $(identify -format "%w" "$1") -lt 228 ] &&

       [ $(identify -format "%h" "$1") -lt 228 ]' _ {} ; 

   -delete -print

This will also print the files that get deleted, you can remove -print if you don't want that.

Not intended to answer but to give a useful tip that helped me much doing bash scripting.

There's a shell script linter called shellcheck that might trap some common errors in bash scripts and also avoid some pitfalls. It can be installed like any package in ubuntu -> https://launchpad.net/ubuntu/+source/shellcheck is in universe for current stable.

This is the output for your script

shellcheck del.sh



In del.sh line 4:

    if [$(identify -format "%w" $i) < 228] && [$(identify -format "%h" $i) < 228];

    ^-- SC1009: The mentioned parser error was in this if expression.

       ^-- SC1073: Couldn't parse this test expression.

        ^-- SC1035: You need a space after the [ and before the ].

                                          ^-- SC1020: You need a space before the ].

                                          ^-- SC1072: Missing space before ]. Fix any mentioned problems and try again.

If you fix and apply again you'll get some other recommendations and fixes already mentioned in the accepted answer.