Adding a header to multiple files

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7.9 Adding a header to multiple files

GNU sed can be used to safely modify multiple files at once.

Add a single line to the beginning of source code files:

sed -i '1i/* Copyright (C) FOO BAR */' *.c

Adding a few lines is possible using ‘\n’ in the text:

sed -i '1i/*\n * Copyright (C) FOO BAR\n * Created by Jane Doe\n */' *.c

To add multiple lines from another file, use 0rFILE. A typical use case is adding a license notice header to all files:

## Create the header file:
$ cat<<'EOF'>LIC.TXT
/*
    Copyright (C) 1989-2021 FOO BAR

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 3, or (at your option)
    any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; If not, see <https://www.gnu.org/licenses/>.
*/
EOF

## Add the file at the beginning of all source code files:
$ sed -i '0rLIC.TXT' *.cpp *.h

With script files (e.g. .sh,.py,.pl files) the license notice typically appears after the first line (the ’shebang’ ‘#!’ line). The 1rFILE command will add FILE after the first line:

## Create the header file:
$ cat<<'EOF'>LIC.TXT
##
## Copyright (C) 1989-2021 FOO BAR
##
## This program is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 3, or (at your option)
## any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this program; If not, see <https://www.gnu.org/licenses/>.
##
##
EOF

## Add the file at the beginning of all source code files:
$ sed -i '1rLIC.TXT' *.py *.sh

The above sed commands can be combined with find to locate files in all subdirectories, xargs to run additional commands on selected files and grep to filter out files that already contain a copyright notice:

find \( -iname '*.cpp' -o -iname '*.c' -o -iname '*.h' \) \
    | xargs grep -Li copyright \
    | xargs -r sed -i '0rLIC.TXT'

Or a slightly safe version (handling files with spaces and newlines):

find \( -iname '*.cpp' -o -iname '*.c' -o -iname '*.h' \) -print0 \
    | xargs -0 grep -Z -Li copyright \
    | xargs -0 -r sed -i '0rLIC.TXT'

Note: using the 0 address with r command requires GNU sed version 4.9 or later. See Zero Address.