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 script with sed to re-write the file.

How do I get sed to replace just the first occurrence of a string in a file rather than replacing every occurrence?

If I use

sed s/#include/#include 'newfile.h'\n#include/ 

it replaces all #includes.

Alternative suggestions to achieve the same thing are also welcome.

Answer 1

 # sed script to change 'foo' to 'bar' only on the first occurrence  1{x;s/^/first/;x;}  1,/foo/{x;/first/s///;x;s/foo/bar/;}  #---end of script--- 

or, if you prefer: ^{Editor’s note: works with GNU sed only.}

sed '0,/foo/s//bar/' file  

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