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From Bash Manual, for filename expansion:

If the nullglob option is set, and no matches are found, the word is removed.

My following script will return exit status 1.

• Can filename expansion failing to match any jpg file in my current directory cause my script to exit with 1?




• How can I rule out other possibility for exit status 1?

Thanks.

shopt -s nullglob

for i in *.png,jpg;
do
 filename=$i##*/
 basename=$filename%.*
 [ ! -e $basename.pdf ] && convert "$i" $basename.pdf ;
done

No, setting the nullglob shell option and failing to expand a glob pattern will not cause the script to exit with a non-zero exit status (and matching filenames with glob patterns in general does not change the $? shell variable).

Not setting nullglob will make convert fail (unless there are files with the literal names *.jpg and *.png in the current directory), and it will exit with an exit status of 1.

Since this is the last executed command in the script, the script will exit with this exit status.

After update to script in question:

The script now exits with a non-zero exit status if a PDF file exists for the last image file processed, due to the [ ! -e ... ] test (this is the last command executed in the script in that case).

If this is unwanted, use

[ ! -e "$basename.pdf" ] && convert "$i" "$basename.pdf" || true

(note also the added quoting)