#!/usr/bin/perl -w
#
# uniq_dirs
#
# AUTHOR:
#   Dan Harkless <software@harkless.org>       http://harkless.org/dan/software/
#
# COPYRIGHT:
#   This file is Copyright (C) 2017 by Dan Harkless, and is released under the
#   GNU General Public License <http://www.gnu.org/copyleft/gpl.html>.
#
# USAGE:
#   % uniq_dirs [<file_1>...]
#
# DESCRIPTION:
#   Takes a list of pathnames and outputs an alpha-sorted list of all the unique
#   directories that contain those files.  The pathnames should be newline-
#   separated, and can be given on stdin, or can be specified inside one or more
#   input files given on the commandline.  I wrote this because commandlines
#   like:
#
#   % locate kill | xargs dirname | sort -u
#
#   can misbehave if there are spaces and/or single quotes in filenames, while
#   commandlines like:
#
#   % locate -0 kill | xargs -0 dirname | sort -u
#
#   can potentially result in an "xargs: argument line too long" error.
#
#   Note that this command is not spelled "unique_dirs", but "uniq_dirs", like
#   the standard UNIX utility "uniq".  Also note that uniq_dirs does not check
#   to see that the named files actually exist in the given directories;
#   dirname() is simply used to differentiate directory from file.
#
# EXAMPLE:
#   % locate kill | uniq_dirs
#   /home/me/Documents/Lizzie B.'s stuff
#   /usr/bin
#   /usr/share/bash-completion/completions
#   /usr/share/man/man1
#   /usr/share/man/man3
#   /usr/share/vim/vim80/syntax
#
# TODO:
#   Add an option to output the files specified on input that are in each
#   directory, using "/some/dir/{file1,file2}" syntax?
#
# DATE        MODIFICATION
# ==========  ==================================================================
# 2017-04-18  Original.


## Modules used ################################################################
use English;         # allow long English names like $ARG instead of $_
use File::Basename;  # for dirname()


## Main ########################################################################
while (<>) {
    $dirs{dirname($ARG)} = 1;
}

foreach $dir (sort(keys(%dirs))) {
    print "$dir\n";
}