uf-headers

#!/bin/sh
#
#  uf-headers - Extract the headers from an unfasta stream.
#  Copyright (C) 2016  Marco van Zwetselaar <io@zwets.it>
#
#  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/>.
#
#  This utility is part of http://io.zwets.it/unfasta

# Function to exit this script with an error message on stderr
err_exit() {
    echo "$(basename "$0"): $*" >&2
    exit 1
}

# Function to show usage information and exit
usage_exit() {
    echo "
Usage: $(basename $0) [OPTIONS] [FILE ...]

  Drop the sequence data and output only the headers from each FILE.
  If no FILE is present or FILE is '-', read from standard input.
" >&2
    exit ${1:-1}
}

# Parse options

while [ $# -ne 0 -a "$(expr "$1" : '\(.\)..*')" = "-" ]; do
    case $1 in
    --help) usage_exit 0 ;;
    *) usage_exit ;;
    esac
    shift || usage_exit
done

gawk -bO 'NR%2==1' "$@"

# vim: sts=4:sw=4:et:si:ai