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.

Answer 1

您可以使用模式匹配：

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

Answer 2

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 

Answer 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.