How to use sed to replace only the first occurrence in a file?

Question

I would like to update a large number of C++ source files with an extra include directive before any existing #includes. For this sort of task, I normally use a small bash s

Answer 1

As an alternative suggestion you may want to look at the ed command.

man 1 ed

teststr='
#include 
#include 
#include 
'

# for in-place file editing use "ed -s file" and replace ",p" with "w"
# cf. http://wiki.bash-hackers.org/howto/edit-ed
cat <<-'EOF' | sed -e 's/^ *//' -e 's/ *$//' | ed -s <(echo "$teststr")
   H
   /# *include/i
   #include "newfile.h"
   .
   ,p
   q
EOF