How to ensure only one file is returned by checking for newline

Question

What is the simplest way to check if a string contains newline?

For example, after

FILE=$(find . -name "pattern_*.sh")

I'd like to check for newline to ensure only one file matched.

score 17 · Answer 1 · answered Jan 27 '12 at 12:23

17

You can use pattern matching:

[[ $FILE == *$'\n'* ]] && echo More than one line

answered Jan 27 '12 at 12:23

choroba

1

This is better without the dollar sign, in my situation. – Master James Nov 03 '16 at 11:56
I came here to answer "check if string contains newline bash", and in my case, I needed `'\r'`, instead of `'\n'`. – gsamaras Dec 17 '18 at 08:55
`\r` is not a newline, see https://stackoverflow.com/q/1761051/1030675. – choroba Dec 17 '18 at 10:30

score 12 · Answer 2 · edited Aug 08 '18 at 19:31

12

If $str contains new line you can check it by,

if [ $(echo "$str" | wc -l) -gt 1 ];
then
     // perform operation if it has new lines
else
     // no new lines.
fi

edited Aug 08 '18 at 19:31

Evgeni Sergeev

answered Jan 27 '12 at 12:18

Shiplu Mokaddim

score 3 · Accepted Answer · answered Jan 27 '12 at 12:25

3

To refer to your example: Note that filenames could contain newlines, too.

A safe way to count files would be

find -name "pattern_*.sh" -printf '\n' | wc -c

This avoids printing the filename and prints only a newline instead.

answered Jan 27 '12 at 12:25

Jo So

Or even `-printf 'x'` to save a character. No need to print newlines. – l0b0 Jan 27 '12 at 15:58
No need - true, but where do you save a character? Choose whatever you feel comfortable with... – Jo So Jan 28 '12 at 11:32

3 Answers3