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Old 04-15-2006, 07:54 AM   #1
Registered: Nov 2005
Distribution: xubuntu, grml
Posts: 451

Rep: Reputation: 37
sed, negate and variable

I'm trying to use sed to search through a text, and replace a variable containing spaces with 'bar'.
But i don't want to replace on lines containing 'foo'.
The reason i want to use a variable is that the sed-command is in a for-loop, so it get's a different variable each loop.

It works when i want to replace on lines with foo:
$ echo ${test}
test1 test2
$ echo ${test// /\\ }
test1\ test2
$ cat file
replace this test1 test2
don't replace when foo test1 test2
$ sed "/foo/s/${test// /\\ }/bar/g" file
replace this test1 test2
don't replace when foo bar
But when i want to negate lines, bash freaks out.
$ sed "/foo/!s/${test// /\\ }/bar/g" file
bash: !s/${test//: event not found
Also, this works of course:
$ sed '/foo/!s/test1\ test2/bar/g' file
replace this bar
don't replace when foo test1 test2
But i have to use double quotes for sed to understand my variable.
Otherwise i get:
$ sed '/foo/s/${test// /\\ }/bar/g' file
sed: -e expression #1, char 17: unknown option to `s'
So, can i negate the regular expression foo without using !
Or can i use sed-branching to test if the regexp foo is not on a line?
Or does anyone have a good hint on how to achieve this? Thanks!
Old 04-15-2006, 08:38 AM   #2
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$ sed "/foo/!s/${test// /\\ }/bar/g" file
When in double quotes, the exclamation point is still a special character which replays a previous command.

You need the sed command in single quotes. You can fragment it so parts that need shell expansion are in double quotes.
sed '/foo/!s/'"${test// /\\ }"'/bar/g' file
Old 04-16-2006, 09:02 AM   #3
Registered: Nov 2005
Distribution: xubuntu, grml
Posts: 451

Original Poster
Rep: Reputation: 37
Ok, it works! I thought i had tried every possible combination of backticks, double/single quotes. Apperently not
Thanks heaps jschiwal!


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