9 SC2144

Vidar Holen edited this page 2022-02-25 20:03:17 -08:00

Table of Contents

• -e doesn't work with globs. Use a for loop.
• Problematic code:
• Correct code:
• Rationale:
• Exceptions
• Related resources:

-e doesn't work with globs. Use a for loop.

Problematic code:

if [ -e dir/*.mp3 ]
then
  echo "There are mp3 files."
fi

Correct code:

for file in dir/*.mp3
do
  if [ -e "$file" ]
  then
    echo "There are mp3 files"
    break
  fi
done

Rationale:

[ -e file* ] only works if there's 0 or 1 matches. If there are multiple, it becomes [ -e file1 file2 ], and the test fails.

[[ -e file* ]] doesn't work at all.

Instead, use a for loop to expand the glob and check each result individually.

If you are looking for the existence of a directory, do:

for f in /path/to/your/files*; do

    ## Check if the glob gets expanded to existing files.
    ## If not, f here will be exactly the pattern above
    ## and the exists test will evaluate to false.
    [ -e "$f" ] && echo "files do exist" || echo "files do not exist"

    ## This is all we needed to know, so we can break after the first iteration
    break
done

Exceptions

If you are sure there will only ever be exactly 0 or 1 matches -- and nullglob is not enabled -- then the test happens to work.

You may still want to consider making this assumption explicit and failing fast if it's ever violated:

files=( dir/file* )
[ "${#files[@]}" -ge 2 ] && exit 1
if [ -e "${files[0]}" ]
then 
  echo "The file exists"
else
  echo "No such file"
fi

Related resources:

• BashFaq: How can I check whether a directory is empty or not? How do I check for any *.mpg files, or count how many there are?
• sh - Check if a file exists with wildcard in shell script - Stack Overflow

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