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 $i fi
doneFor some reasons, I got this output when I run it:
./del.sh: line 4: [640: command not found
./del.sh: line 4: [550: command not found
./del.sh: line 4: [315: command not found
...Could you please tell me what's wrong in this script and how to fix it.
Thank you.
EDIT: Even after I added spaces after the brackets, I still got an error. It was due to the usage of < instead of -lt and has been fixed. Now there is no error.
3 Answers
Some issues here: Firstly, the expression in a […] test needs spaces around it (pitfall #10), and secondly
the comparison < doesn't work with […] tests (pitfall #7). You either need -lt (less than)
or use [[…]] instead, which is a bashism. Also, the for loop should be replaced (pitfall #1).
So:
for i in ./*; do if [ -e "$i" ]; then if [ $(identify -format "%w" "$i") -lt 228 ] && [ $(identify -format "%h" "$i") -lt 228 ]; then rm -- "$i" fi fi
doneYou may also want to avoid calling identify twice to get the two dimensions (pitfall #58) but call
it just once instead and let it print a string ready to be used as variable assignments in shell syntax.
If we write
identify -format "width=%w height=%h" "$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"
fiSee also: common bash pitfalls.
0Instead 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" "$1") -lt 228 ]' _ {} \; \ -delete -printThis will also print the files that get deleted, you can remove -print if you don't want that.
Not intended to answer but to give a useful tip that helped me much doing bash scripting.
There's a shell script linter called shellcheck that might trap some common errors in bash scripts and also avoid some pitfalls. It can be installed like any package in ubuntu -> is in universe for current stable.
This is the output for your script
shellcheck del.sh
In del.sh line 4: if [$(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.
