stripfilt

#!/usr/bin/awk -f
#
# Copyright (c) 2012, 2015, 2016 Douglas G. Scofield, Uppsala University
# douglas.scofield@ebc.uu.se
# douglasgscofield@gmail.com
#
# This code is covered by the Gnu GPLv2, please see LICENSE.
# Bugs and suggestions to https://github.com/douglasgscofield/tinyutils/issues.
#
# Strip out header and comment lines, or pass through only header and comment lines.
# Also handles empty/blank lines with skip_blank=1 option.
#
# CHANGELOG
# 2016-07-09 : add inverse_early
# 2013-05-15 : make FS and OFS be "\t" by default
# 2012-12-04 : create the script


BEGIN {
    # parameters
    FS = "\t"; 
    OFS = "\t"; 
    header = 1;        # does the input have a header? if so how many lines?
    skip_comment = 1;  # skip '#' lines on input
    skip_blank = 0;    # skip empty lines or those only containing whitespace?
    inverse = 0;       # do we instead only print the header and comments?
    inverse_early = 1; # with inverse=1, do we stop when we see the first non-skipped line?
}

{
    if (NR <= header) {
        if (inverse)
            print;
        next;
    }
    if (NR > header && inverse && ! skip_comment && ! skip_blank)
        exit;
    if (skip_comment && $0 ~ /^#/) {
        if (inverse)
            print;
        next;
    }
    if (skip_blank && $0 ~ /^[ \t]*$/) {
        if (inverse)
            print;
        next;
    }
    if (! inverse)
        print;
    else if (inverse_early)
        exit;
}