✏ EDIT: mdate-sh

#!/bin/sh
# Get modification time of a file or directory and pretty-print it.

scriptversion=2018-03-07.03; # UTC

# Copyright (C) 1995-2018 Free Software Foundation, Inc.
# written by Ulrich Drepper <drepper@gnu.ai.mit.edu>, June 1995
#
# 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 2, 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 <https://www.gnu.org/licenses/>.

# As a special exception to the GNU General Public License, if you
# distribute this file as part of a program that contains a
# configuration script generated by Autoconf, you may include it under
# the same distribution terms that you use for the rest of that program.

# This file is maintained in Automake, please report
# bugs to <bug-automake@gnu.org> or send patches to
# <automake-patches@gnu.org>.

if test -n "${ZSH_VERSION+set}" && (emulate sh) >/dev/null 2>&1; then
  emulate sh
  NULLCMD=:
  # Pre-4.2 versions of Zsh do word splitting on ${1+"$@"}, which
  # is contrary to our usage.  Disable this feature.
  alias -g '${1+"$@"}'='"$@"'
  setopt NO_GLOB_SUBST
fi

case $1 in
  '')
     echo "$0: No file.  Try '$0 --help' for more information." 1>&2
     exit 1;
     ;;
  -h | --h*)
    cat <<\EOF
Usage: mdate-sh [--help] [--version] FILE

Pretty-print the modification day of FILE, in the format:
1 January 1970

Report bugs to <bug-automake@gnu.org>.
EOF
    exit $?
    ;;
  -v | --v*)
    echo "mdate-sh $scriptversion"
    exit $?
    ;;
esac

error ()
{
  echo "$0: $1" >&2
  exit 1
}

# Prevent date giving response in another language.
LANG=C
export LANG
LC_ALL=C
export LC_ALL
LC_TIME=C
export LC_TIME

# Use UTC to get reproducible result.
TZ=UTC0
export TZ

# GNU ls changes its time format in response to the TIME_STYLE
# variable.  Since we cannot assume 'unset' works, revert this
# variable to its documented default.
if test "${TIME_STYLE+set}" = set; then
  TIME_STYLE=posix-long-iso
  export TIME_STYLE
fi

save_arg1=$1

# Find out how to get the extended ls output of a file or directory.
if ls -L /dev/null 1>/dev/null 2>&1; then
  ls_command='ls -L -l -d'
else
  ls_command='ls -l -d'
fi
# Avoid user/group names that might have spaces, when possible.
if ls -n /dev/null 1>/dev/null 2>&1; then
  ls_command="$ls_command -n"
fi

# A 'ls -l' line looks as follows on OS/2.
#  drwxrwx---        0 Aug 11  2001 foo
# This differs from Unix, which adds ownership information.
#  drwxrwx---   2 root  root      4096 Aug 11  2001 foo
#
# To find the date, we split the line on spaces and iterate on words
# until we find a month.  This cannot work with files whose owner is a
# user named "Jan", or "Feb", etc.  However, it's unlikely that '/'
# will be owned by a user whose name is a month.  So we first look at
# the extended ls output of the root directory to decide how many
# words should be skipped to get the date.

# On HPUX /bin/sh, "set" interprets "-rw-r--r--" as options, so the "x" below.
set x`$ls_command /`

# Find which argument is the month.
month=
command=
until test $month
do
  test $# -gt 0 || error "failed parsing '$ls_command /' output"
  shift
  # Add another shift to the command.
  command="$command shift;"
  case $1 in
    Jan) month=January; nummonth=1;;
    Feb) month=February; nummonth=2;;
    Mar) month=March; nummonth=3;;
    Apr) month=April; nummonth=4;;
    May) month=May; nummonth=5;;
    Jun) month=June; nummonth=6;;
    Jul) month=July; nummonth=7;;
    Aug) month=August; nummonth=8;;
    Sep) month=September; nummonth=9;;
    Oct) month=October; nummonth=10;;
    Nov) month=November; nummonth=11;;
    Dec) month=December; nummonth=12;;
  esac
done

test -n "$month" || error "failed parsing '$ls_command /' output"

# Get the extended ls output of the file or directory.
set dummy x`eval "$ls_command \"\\\$save_arg1\""`

# Remove all preceding arguments
eval $command

# Because of the dummy argument above, month is in $2.
#
# On a POSIX system, we should have
#
# $# = 5
# $1 = file size
# $2 = month
# $3 = day
# $4 = year or time
# $5 = filename
#
# On Darwin 7.7.0 and 7.6.0, we have
#
# $# = 4
# $1 = day
# $2 = month
# $3 = year or time
# $4 = filename

# Get the month.
case $2 in
  Jan) month=January; nummonth=1;;
  Feb) month=February; nummonth=2;;
  Mar) month=March; nummonth=3;;
  Apr) month=April; nummonth=4;;
  May) month=May; nummonth=5;;
  Jun) month=June; nummonth=6;;
  Jul) month=July; nummonth=7;;
  Aug) month=August; nummonth=8;;
  Sep) month=September; nummonth=9;;
  Oct) month=October; nummonth=10;;
  Nov) month=November; nummonth=11;;
  Dec) month=December; nummonth=12;;
esac

case $3 in
  ???*) day=$1;;
  *) day=$3; shift;;
esac

# Here we have to deal with the problem that the ls output gives either
# the time of day or the year.
case $3 in
  *:*) set `date`; eval year=\$$#
       case $2 in
	 Jan) nummonthtod=1;;
	 Feb) nummonthtod=2;;
	 Mar) nummonthtod=3;;
	 Apr) nummonthtod=4;;
	 May) nummonthtod=5;;
	 Jun) nummonthtod=6;;
	 Jul) nummonthtod=7;;
	 Aug) nummonthtod=8;;
	 Sep) nummonthtod=9;;
	 Oct) nummonthtod=10;;
	 Nov) nummonthtod=11;;
	 Dec) nummonthtod=12;;
       esac
       # For the first six month of the year the time notation can also
       # be used for files modified in the last year.
       if (expr $nummonth \> $nummonthtod) > /dev/null;
       then
	 year=`expr $year - 1`
       fi;;
  *) year=$3;;
esac

# The result.
echo $day $month $year

# Local Variables:
# mode: shell-script
# sh-indentation: 2
# eval: (add-hook 'before-save-hook 'time-stamp)
# time-stamp-start: "scriptversion="
# time-stamp-format: "%:y-%02m-%02d.%02H"
# time-stamp-time-zone: "UTC0"
# time-stamp-end: "; # UTC"
# End:

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