Initializes files with GPL or adds it to existing files.

gpl-init.sh

#!/bin/bash
#    A small tool to init files with a GPL header.
#    Copyright (C) 2015 Christoph "criztovyl" Schulz
#
#    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 of the License, 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 <http://www.gnu.org/licenses/>.
if [[ "$1" =~ ^-{0,2}h(elp)?$ ]]; then
    echo -e "Usage: $0 filename.type"
    echo "Will open file afterwards, supress this by setting \$GI_NOPOSTPROG to any value."
    echo "By default is interactive (asks you for description and author)."
    echo " To disable this completly set \$GI_NOINTERACTIVE to any value."
    echo " You also can define \$GI_SUMMARY and/or \$GI_AUTHOR to use these values instead of asking."
    exit 1
fi

# postprog - program to run after initialisation, {} will be replaced with file name
postprog="vim {}"
prefix=".gpl-init"
filename=$1
year=`date +%Y`

[ "$filename" ] || exit 5

ext=${filename##*.}

for name in summary author; do
    var=GI_${name^^}
    [ "${!var}" ] &&
    eval $name=\"${!var}\"
    if [ -z "${!name}" ]; then
        if [ -f ".gi_${name,,}" ]; then
            echo "Using summary file .gi_${name,,}"
            eval $name=\"`cat ".gi_${name,,}"`\"
        elif [ -z "$GI_NOINTERACTIVE" ]; then
            read -p "${name^}: " $name
        fi
    fi
done

# Disable globbing, "/*" would cause problems otherwise
# Remember if was already disabled
[[ "$-" == *f* ]] && noglob=true
set -f

# Determine comment type
case $ext in
    sh|bash)
        firstline="#!/bin/bash"
        fc="#"
        lastline=""
        ;;
    php)
        firstline='<?php\n/*'
        fc=""
        lastline=' */'
        ;;
    py)
        firstline='"""'
        fc=""
        lastline='"""'
        ;;
    rb)
        firstline="#!/usr/bin/env ruby"
        fc="#"
        ;;
esac

# Create Header

gpl=""

# mapfile callback
callback(){ gpl=$gpl$2"\n"; }

mapfile -c 1 -C callback <<gpl
$firstline
$fc    $summary
$fc    Copyright (C) $year $author
$fc
$fc    This program is free software: you can redistribute it and/or modify
$fc    it under the terms of the GNU General Public License as published by
$fc    the Free Software Foundation, either version 3 of the License, or
$fc    (at your option) any later version.
$fc
$fc    This program is distributed in the hope that it will be useful,
$fc    but WITHOUT ANY WARRANTY; without even the implied warranty of
$fc    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
$fc    GNU General Public License for more details.
$fc
$fc    You should have received a copy of the GNU General Public License
$fc    along with this program.  If not, see <http://www.gnu.org/licenses/>.
$lastline
gpl

# Copy the file to preserve file permissions
[ -f $filename ] && cp $filename $filename$prefix

# Put header into file
echo -e $gpl > $filename$prefix

# If file exists, append contents
[ -f $filename ] && cat $filename >> $filename$prefix

#Re-enable globbing if wasn't disabled before
[[ "$noglob" = true ]] || set +f

# Backup original file
[ -f $filename ] && cp $filename $filename$prefix-bak

# Overwrite real file with header + file contents
mv -f $filename$prefix $filename

if [ -z "$NOPOSTPROG" ]; then
    # Replace {} with filename in post-program
    postprog=${postprog//\{\}/$filename}

    # Does not work; not an interactive shell.
    # Add post-program to history
    #history -s $postprog

    # Run post-program
    $postprog
fi