How to prepend a license header recursively for all .h and .cpp files in a directory

Question

I'm trying to add a license header to all header files and source files in a project directory using a for loop. This is not working, is there any other approach using sed?

Answer 1

for f in **/*.cpp; do
  cat header_file $f > $f.new
  mv $f.new $f
done

Answer 2

This is more or less just an extended commentary on Daniel Serodio'` answer. I started writitng it as a comment, but it quickly grew too large...

For a bash glob to be recursive, it requires shopt -s globstar. You must enable globstar, otherwise ** doesn't work. The globstar shell option was introduced to version 4 of bash.

To avoid processing a directory such as my.cpp/, use the test [[ -f $f ]]... When the test is in double square-brackets, variables don't need to be double quoted.

You can also consider the possibility of there being no matching files by using shopt -s nullglob, which allows patterns which match no files to expand to a null string, rather than themselves.

To handle multiple patterns, you can chain the glob patterns: **/*.cpp **/*.h, but perhaps preferrably, when the shell option extglob is on via shopt -s extglob, you can use such constructs such as **/*.@(cpp|h) which avoids multiple passes over the file system; once for each pattern.

If you want .files to be included, use .*.cpp etc, or use shopt -s dotglob

To safely handle modifying a file which is being piped, use sponge from package moreutils (it saves you the need to create your own temp file)

---

printf "// The License\n\n" > /tmp/$USER-license

shopt -s globstar nullglob extglob
for f in **/*.@(cpp|h) ;do
  [[ -f $f ]] && cat "/tmp/$USER-license" "$f" | sponge "$f"
done

Answer 3

Thank you @fred, @maxmackie, @enzotib.

Can you please check the procedure I have followed.

#!/bin/sh
# script to copy the headers to all the source files and header files
for f in *.cpp; do
  if (grep Copyright $f);then 
    echo "No need to copy the License Header to $f"
  else
    cat license.txt $f > $f.new
    mv $f.new $f
    echo "License Header copied to $f"
  fi 
done   

otherwise the license header will be copied to multiple number of times.

Please suggest me a pattern to go through all the headers and sources in project directory and subdirectories.

I could not understand fully what @fred has suggested.

Answer 4

You can do this with ex or ed if you prefer (you should not do this with sed as you requested, sed is designed to edit streams, -i is a bad idea for a variety of reasons):

shopt -s globstar

for _file in **/*.@(cpp|h); do
    ed -s "${_file}" << EOF
0a
/* This file is licensed under the foo license.
   All copyright strictly enforced by the copyright monster. /*
.
w
EOF
    done