Using sed command in variable

Question

I have the following variable TABLES with multiple lines

TABLES="foobar
test
bar
foo
"

I have a variable SKIP with this sed command

$ echo $SKIP
/bar/d;/foo/d;

I want to use it on sed, like this

echo $TABLES | sed "$SKIP"

But this returns nothing! If I replace the variable with the current content it works

What I am doing wrong?

You just needed to quote your shell variables so `echo "$TABLES" | sed "$SKIP"` would have worked as well — anubhava, Jun 28 '22 at 16:17
Does this answer your question? [sed with literal string--not input file](https://stackoverflow.com/questions/13055889/sed-with-literal-string-not-input-file) — Wiktor Stribiżew, Jun 28 '22 at 17:03

score -3 · Answer 1 · answered Jun 28 '22 at 20:48

What I am doing wrong?

You are not quoting variable expansion. Unquoted variable expansion undergo word splitting, which splits the result of expansion also on newlines, changing it into words. You are doing:

echo foobar test bar foo | ...

Because echo joins the arguments with space, this is effectively one line. /bar/d removes that line.

Quote variable expansion to prevent word splitting. Check your scripts with shellcheck.

echo "$TABLES" | sed "$SKIP"

Using sed command in variable

1 Answers1