Issue
I have a script variable which is multi-line. How do i traverse this variable to read it line by line and process each line the way I want?
Solution
Consider the following multi-line variable
x=$(echo -e "a\nb\nc d e")
and a simple process for each line: just echo it with a prefix=LINE: and with single quotes around the line. Either of the following codes will satisfy that requirement:
while read line; do echo "LINE: '${line}'"; done <<< "$x"
or
while read line; do echo "LINE: '${line}'"; done < <(echo "$x")
Neither creates a subshell (so you can, e.g., set variables in the loop and access them outside of it), and both output
LINE: 'a'
LINE: 'b'
LINE: 'c d e'
But suppose instead you have
x=$(echo -e "a \n b\nc d e")
# note--------^--^
and that leading and trailing whitespace matter for your application (e.g., parsing Git porcelain). Both the above codes will give exactly the same output for the latter variable/data as for the former, which is not what you want. To preserve leading and trailing whitespace, replace while read line with while IFS= read -r line . I.e., either of the following codes
while IFS= read -r line; do echo "LINE: '${line}'"; done <<< "$x"
or
while IFS= read -r line; do echo "LINE: '${line}'"; done < <(echo "$x")
will produce
LINE: 'a '
LINE: ' b'
LINE: 'c d e'
See Greg Wooledge's excellent Bash FAQ for details.
Answered By - Karoly Horvath