correct use of delimiter in sed regex

Question

New to sed, so trying to figure out following problem.

sed -e "s/menuentry \"test.*(/menuentry \"test image ${VERSION} (/" \
    -e "s/menuentry \"Lost password change.*(/menuentry \"Lost password change ${VERSION} (/" \
    -e "sX/boot/[A-Za-z0-9\.\-\@_]*X/boot/${VERSION}Xg" \
    < test.txt

Above expression, the 3rd part

-e "sX/boot/[A-Za-z0-9\.\-\@_]*X/boot/${VERSION}Xg" gives an error

sed: -e expression #3, char 37: unknown option to `s' if $VERSION=FIX i.e contains "X".

What is the better way to deal with this? use another character as a delimiter, i tried ":" and it worked.

Well, as you say, you can get around this using a different delimiter. There's your answer. — elixenide, Dec 15 '14 at 04:36
why'd you use double quotes? If you're not going to reference some like a variable or a cmd (e.g. `$(CMD)` or `$VAR`) then you'd probably be better off using single quotes: `sed '/regex/'`. That way you don't have ugly nested double quotes. Don't use double quotes unless you _need_ them. — Alexej Magura, Dec 15 '14 at 04:43
other delimiter right or escape the delimiter character in your variable (using a temporary variable or `$( )` or a shell variable modification during the substitution — NeronLeVelu, Dec 15 '14 at 06:56

score 1 · Answer 1 · answered Dec 15 '14 at 08:53

awk to the rescue!

VERSION=FIX

awk -v VERSION="$VERSION" \
    '{
       sub (/menuentry "test.*\(/                , "menuentry \"test image " VERSION " ("          );
       sub (/menuentry "Lost password change.*\(/, "menuentry \"Lost password change " VERSION " (");
       gsub("/boot/[A-Za-z0-9.@_-]*"             , "/boot/" VERSION                                );
       print;
     }' \
    < foo.txt

Substituting variables into sed commands is Not A Good Idea™, precisely for the reasons you encountered. When you find yourself tempted to do that, consider using awk instead. It's less sexy, but it does not have this particular problem.

correct use of delimiter in sed regex

1 Answers1