pem-op, splitting pem file

pem-op

#!/bin/bash
#
# Copyright (c) 2018, Red Hat, Inc.
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#

print_help()
{
    local prog=$1
    local status=$2

    echo "Usage:"
    echo "	$prog help|--help|-h"
    echo "	$prog count PEMFILE"
    echo "	$prog extract N PEMFILE"
    echo "	$prog list PEMFILE"    
    echo "Note:"
    echo "	N starts from 0."
    echo "	Use \"-\" for reading pemfile from the standard input."

    exit $status
}

do_count_or_list ()
{
    local file=$1
    shift

    if [ $# -gt 0 ]; then
	echo "too many arguments" 1>&2
	return 1
    fi

    if [ -z "$file" ]; then
	file=-
    fi

    if [ "$file" = '-' ]; then
	file=/dev/stdin
    fi

    if [[ ! -e "$file" ]]; then
	echo "no such file: $file" 1>&2
	return 1
    fi

    if [ ! -r "$file" ]; then
	echo "$file is not readable" 1>&2
	return 1
    fi

    if [ -d "$file" ]; then
	echo "$file must be a file" 1>&2
	return 1
    fi

    grep -e '^-----BEGIN' < $file
    return 0
}

do_count ()
{
    do_count_or_list "$@" | wc -l
}

do_list ()
{
    do_count_or_list "$@" | sed -n -e 's/^-----BEGIN \+\(.\+\)-----$/\1/p' | cat -n
}

print_pem ()
{
    local old_ifs=$IFS
    local in_range=0
    local not_found=2
    
    while read LINE; do
	case "$LINE" in
	    -----BEGIN*)
		echo "$LINE"
		in_range=1
		;;
	    -----END*)
		echo "$LINE"
		not_found=0
	    break
	    ;;
	    *)
		if [[ $in_range == 1 ]]; then
		    echo "$LINE"
		fi
	    ;;
	esac
    done
    
    return $not_found
}

do_extract ()
{
    local n=$1
    local file=$2

    if [ -z "$n" ]; then
	echo "no ordinal number is given" 1>&2
	return 1
    fi

    if [[ ! "$n" =~ [0-9]+$ ]]; then
	echo "wrong format as ordinal number: \"$n\"" 1>&2
	return 1
    fi
    
    if [[ "$n" =~ ^0.* ]]; then
        echo "The first argument START should not start from 0" 1>&2
        return 1
    fi

    if [ -z "$file" ]; then
	file=-
	return 1
    fi

    if [ "$file" = '-' ]; then
	file=/dev/stdin
    fi

    if [[ ! -e "$file" ]]; then
	echo "no such file: $file" 1>&2
	return 1
    fi

    if [ ! -r "$file" ]; then
	echo "$file is not readable" 1>&2
	return 1
    fi

    if [ -d "$file" ]; then
	echo "$file must be a file" 1>&2
	return 1
    fi
    
    local status=2
    local out=/dev/null
    n=$((n - 1))
    for ((i = 0; i <= n; i++)); do
	if (( i == n )); then
	    out=/dev/stdout
	fi
	print_pem > $out
	status=$?
    done < $file

    return $status
}

case $1 in
    --help|-h|help)
	print_help $0 0
	;;
    count)
	shift
	do_count "$@"
	exit $?
	;;
    list)
	shift
	do_list "$@"
	exit $?
	;;
    extract)
	shift
	do_extract "$@"
	exit $?
	;;
    *)
	echo "unexpected argument $1" 1>&2
	print_help $0 1 1>&2
	;;
esac