Why is read hanging my bash script?

Question

I had a similar problem to this with Python using readlines() but I'm not sure if it's the same here.

The read command is hanging my bash script.

generate_email()
{
    # --- Arguments
    oldrev=$(git rev-parse $1)
    newrev=$(git rev-parse $2)
    refname="$3"

    # ... some code ...
}

# ... more code ...

while read oldrev newrev refname
do
    generate_email $oldrev $newrev $refname
done

Any ideas on how to fix this?

Answer 1

You're not telling read to read from anything. So it's just waiting for input from stdin.

If you're wanting to read from a file, you need to use read like so:

while read -r oldrev newrev refname; do
  generate_email "$oldrev" "$newrev" "$refname"
done < /path/to/file

Note the < /path/to/file. That's where you're actually telling read to read from the file.

If you're wanting to read from an input stream, you can use while read like so:

grep 'stuffInFile' /path/to/file |
while read -r oldrev newrev refname; do
  generate_email "$oldrev" "$newrev" "$refname"
done

Answer 2

I'd say it's not hanging, but just waiting for input.

Watch out though and make sure that generate_email does not read from the same input stream.