Pattern matching in filenames

Asked Mar 28 '21 at 00:15

Active Mar 28 '21 at 00:15

Viewed 46 times

I'm trying to refresh my bash scripting skills. I got stuck on the dumbest thing:

for f in "$(ls)"; do
    [[ $f == *.txt ]] && printf "%s\n" "$f"
done

What is wrong with this loop? I'm simply trying to print all the .txt files in the current dir. It seems that pattern match is wrong..

asked Mar 28 '21 at 00:15

alfredopacino

5

First read Why not parse ls (and what to do instead)?. Then you don't need a loop for that, ls *.txt will do. Also this. – schrodingerscatcuriosity Mar 28 '21 at 00:28
2

Also, in this case, using set -x to see the command being executed after expansions will likely be revealing. – fra-san Mar 28 '21 at 00:59
@schrodigerscatcuriosity I'll read that, but this just a toy script I've made and I'm curious about why it doesn't work. – alfredopacino Mar 28 '21 at 18:21
@fra-san In this case the debug mode doesn't help I think, it just prints out the whole list I'm iterating over, and the list contains both .txt and not .txt files – alfredopacino Mar 28 '21 at 18:23
@alfredopacino that's waht fra-san was pointing out. The double-quotes in the command substitution causes the list of files to be printed as one line, remove the dqs. – schrodingerscatcuriosity Mar 28 '21 at 18:57
1

...and it will make clear that 1) the loop body is executed just once, no matter how many files are listed by ls; 2) the whole list of files matches the pattern *.txt if the last file name ends in .txt, no matter what the other file names are. – fra-san Mar 28 '21 at 20:30

0 Answers0