Subshell and sed

TaytoMan69

Hi all, I have a small piece of a script here that is supposed to remove prefixes from variables based on the contents of a table stored in a tmp file

The issue arises when I cat the table and pipe it into the while loop, as it creates a subshell the data won't be returned.

Searching online the advice to use 'here strings' is valid but still the output is blank.
<<< "$(echo "$line")"

************************************
cat $ZXDSA | while read line; do
p1=$(echo $n1 | sed "s|^\\$line ||g")
p2=$(echo $n2 | sed "s|^\\$line ||g")
done

echo $p1
echo $p2
************************************
Can anybody explain the process of how to return a value without losing the data within the loop.

Keplar240B

Are you aware of the shellcheck tool?

I don't have time to debug right now but Shellcheck offers some hints

https://www.shellcheck.net/

Line 2:
cat $ZXDSA | while read line; do
^-- SC2086: Double quote to prevent globbing and word splitting.
^-- SC2002: Useless cat. Consider 'cmd < file | ..' or 'cmd file | ..' instead.
^-- SC2162: read without -r will mangle backslashes.

Line 3:
p1=$(echo $n1 | sed "s|^\\$line ||g")
^-- SC2030: Modification of p1 is local (to subshell caused by pipeline).
^-- SC2001: See if you can use ${variable//search/replace} instead.
^-- SC2154: n1 is referenced but not assigned.
^-- SC2086: Double quote to prevent globbing and word splitting.

Line 4:
p2=$(echo $n2 | sed "s|^\\$line ||g")
^-- SC2030: Modification of p2 is local (to subshell caused by pipeline).
^-- SC2001: See if you can use ${variable//search/replace} instead.
^-- SC2154: n2 is referenced but not assigned.
^-- SC2086: Double quote to prevent globbing and word splitting.

Line 7:
echo $p1
^-- SC2031: p1 was modified in a subshell. That change might be lost.
^-- SC2086: Double quote to prevent globbing and word splitting.

Line 8:
echo $p2
^-- SC2031: p2 was modified in a subshell. That change might be lost.
^-- SC2086: Double quote to prevent globbing and word splitting.

Zab

If you use a redirect instead of a pipe it should work:

while read line; do
p1=$(echo $n1 | sed "s|^\\$line ||g")
p2=$(echo $n2 | sed "s|^\\$line ||g")
done < $ZXDSA

echo $p1

TaytoMan69

To get around the issue, I ended up using a here string. Success!

while read line; do
p1=$(sed "s|^\\$line ||g" <<< $s1)
p2=$(sed "s|^\\$line ||g" <<< $s2)
done <<< "$table"