How to insert a line just after the first regex match with sed?

Question

I have a few CmakeLists.txt files and I would like to insert another include right after a known include. So, here's what I've got:

include_directories(src include)

And, here's what I would like to end up with

include_directories(src include)
include_directories("${CMAKE_INSTALL_PREFIX}/include")

Any ideas on the best way to do this? I'm assuming sed would make the most sense, but I'm open to alternatives.

[edit] Found a duplicate question.

Answer 1

You can use this simple sed command with inline editing:

sed -i.bak '/include_directories(src include)/a\
include_directories("${CMAKE_INSTALL_PREFIX}/include")
' CmakeLists.txt

• This uses a command which appends a new string after searched string.
• -i.bak is for incline editing of the input file.

Answer 2

If you're not satisfied with the answer to the duplicate question, you could try this:

sed '/include_directories(src include)/s/$/\
include_directories(\"${CMAKE_INSTALL_PREFIX}\/include\")/' filename

This might or not work, depending on your shell. If it doesn't, the lesson is to attempt simple things first, then build up.

Answer 3

sed is an excellent tool for simple substitutions on a single line but for anything else you're better off with awk:

awk '{print} /include_directories\(src include\)/{print "include_directories(\"${CMAKE_INSTALL_PREFIX}/include\")"}' file

Answer 4

Another awk variation:

awk '/include_directories\(src include\)/{$0=$0 "\ninclude_directories(\"${CMAKE_INSTALL_PREFIX}/include\")"}8' file

If pattern found, add a new line to current line, then print all.