xdate

#!/bin/sh
# This is a messy pile of posix shell, awk, & perl. TODO: all perl or no perl?

help() {	# assemble --help from GNU date's --help plus extras
  self="${0##*/}"
  cat <</short_help
Usage: xdate [OPTION]... [+FORMAT]
Show the current time. Formats include YYYYMMDD_HHMMSS & xlsDDDDD[.DDD] (Excel)

  -d, --date=STRING      Display time described by STRING, not 'now'
      --debug            Annotate the parsed date, noting questionable usage
  -f, --file=DATEFILE    Like --date; once for each line of DATEFILE
  -I, --iso-8601[=FMT]   Output date/time in ISO 8601 format.
  -R, --rfc-email        Output date and time in RFC 5322 format.
      --rfc-3339=FMT     Output date/time in RFC 3339 format.
  -r, --reference=FILE   Display the last modification time of FILE
      --ss-format=FMT    Spreadsheet date format: \`excel\`, \`mac\`, or \`ooo\`
  -s, --set=STRING       Set time described by STRING
  -u, --utc, --universal Print or set Coordinated Universal Time (UTC)
  -x, --exec=PATH        Run the date command with PATH, not \`date\`
  -h, --help             Display brief help and exit
  -h, --long-help        Display comprehensive help and exit
  -V, --version          Output version information and exit

/short_help
  if [ "$1" = --long ]; then
    cat <</long_help

Excel does not deal with time zones or daylight savings (DST). Because of that,
$self makes everything relative to the *current* DST offset.  Converting back
to a standard date in $self may be an hour off, but it should work in Excel.

$self defaults to OpenOffice dates before 1899/12/31 and Excel afterwords:

  --ss-format=  NOTES             DAY 1        DAY 59     DAY 60      Day 61
  (default)     OO then Excel   1899/12/31  1900/02/28  1900/02/28  1900/03/01
  excel         Leap year bug   1900/01/01  1900/02/28  1900/02/28  1900/03/01
  openoffice                    1899/12/31  1900/02/27  1900/02/28  1900/03/01
  mac           Excel for Mac   1904/01/01  1904/02/28  1904/02/29  1904/03/01

Learn more at https://stackoverflow.com/a/32578059/519360"

/long_help

    "$gdate" --help 2>&1 |awk -v self="$self" '
      function opt(option, desc) { return sprintf("%-*s%s", i, option, desc) }
      function popt(option, desc) { print opt(option, desc) }
      /^date: illegal/	{ bsd = 1; next }
      $1 == "FORMAT"	{ format_section = 1 }
      ! format_section	{ next }
      /^Examples/i	{ examples = 1 }
      /^Report bugs/	{ print "Convert Excel time to a date"
      			  print "  $ xdate --date=12345\n" }
      /(^|[,:$] +)date/	{ sub (/date/, self) }
      { print }
      $1 == "%j"  { sub(/j/, "J"); sub(/ of.*/, "s after 1899/12/30"); print }
      END 	{ if (bsd) print "\nLearn more about formats: `man strftime`" }
    '
    echo "xdate wrapper home page: <https://github.com/adamhotep/misc-scripts>"
    echo ""
  else
    echo ""
    echo "Part of misc-scripts: https://github.com/adamhotep/misc-scripts"
  fi
  echo "xdate 0.3.20260315.0 copyright 2010+ by Adam Katz, GPLv3+"
  exit
}

debug() { [ -n "$DEBUG" ] && echo "$*" >&2; }

xls_epoch=0 # calculated on first use since it's only used with -d and -f

# Usage: map_dates_filter
# Preprocessor for date's --date=STRING and --file=DATEFILE
# accept more date formats: YYYYMMDD_HHMMSS, DDDDD.DDD, xlsDDDDD[.DDD]
map_dates_filter() {
  # Unix epoch offset of Excel epoch https://stackoverflow.com/a/32578059/519360
  if [ "$xls_epoch" -ge 0 ]; then
    # nested call works around Excel's lack of understanding of daylight savings
    local TZ="$(date +%z)"
    xls_epoch="$(( xls_epoch + $("$gdate" -d "1899/12/30 00:00:00 $TZ" +%s) ))"
  fi
  awk -v xls="$xls" -v xls_epoch="$xls_epoch" '
    NF == 1 && $1 ~ /^[0-9]+_[0-9]+(\.[0-9]*)?$/ \
    && $1 ~ /^[12]...[01].[0-3]._[0-2].([0-6].([0-6].(\.[0-9]*)?)?)?$/ {
      $0 = sprintf("%04d/%02d/%02d %02d:%02d:%02d\n",
        substr($0, 1, 4), substr($0, 5, 2), substr($0, 7, 2),
        substr($0, 10, 2), substr($0, 12, 2), substr($0, 14))
    }
    /^xls[+-]?[0-9]+(\.[0-9]*)?$/ { sub(/^xls\+?/, "", $1); x = 1 }
    x || /^-?[0-9]+$/ && 2359 < $1/1 && $1/1 < 99999 || /^(-?[0-9]+\.[0-9]*)$/ {
      if (($1 >= 0 || xls == 2) && $1 < 60 && xls) $1++; # Excel bug
      $0 = sprintf("@%.0f\n", xls_epoch + $1 * 86400)
      x = 0
    }
    1
  ' "$@"

  return
  # why 2360-100101? because 2359 = "today at 23:59" and 100101 = "2010/01/01"
 #perl -ne '
 #  if (/^[12]\d\d\d[01]\d[0-3]\d_[0-2]\d([0-6]\d([0-6]\d)?)?(\s|$)/) {
 #    printf "%04d/%02d/%02d %02d:%02d:%02d\n",
 #      substr($_,0,4), substr($_,4,2), substr($_,6,2),
 #      substr($_,9,2), substr($_,11,2), substr($_,13);
 #  } elsif (2359 < $_ && $_ < 100101 || /^-?[0-9]*\.[0-9]*$/) {
 #    $_++ if ($_ >= 0 or $ENV{xls} == 2) and $_ < 60 and $ENV{xls}; # Excel bug
 #    printf "@%.0f\n", $ENV{xls_epoch} + $_ * 86400
 #  } else { print; }
 #' "$@"
}

# convert file or string to mapped version
tmp=
trap_codes="0 1 2 5 9 11 15 18"
trap "rm -f $tmp" $trap_codes	# has to be outside the function
map_dates() {
  if [ -t 0 ] && ! [ -e "$1" ]; then	# no standard input, not given a file
    printf "%s\n" "$@" |map_dates_filter
  else
    tmp="$(mktemp "${TMPDIR:-/tmp}/xdate.${pid}XXXX")"
    map_dates_filter "$@" > "$tmp"
    echo "$tmp"
  fi
}


# Getopts can't handle altering values, nor can it handle optional arguments
reset= next= xls=1 pid=$$ gdate=date long=
for arg in "$@"; do
  debug "HERE looping on <$arg>"
  if [ -z "$reset" ]; then reset=1; set --; fi
  if [ -n "$next" ]; then
    case $next in
      ( -[df] ) 	set -- "$@" "$next" "$(map_dates "$arg")" ;;
      ( -x )		gdate="$arg" ;;
      ( --ss-format )	ss_fmt="$arg" ;;
      ( -* )		set -- "$@" "$next" "$arg" ;;
    esac
    next=
    continue
  fi

  if [ "$arg" != "${arg#-[!-]}" ]; then
    opt="${arg#-}"
    while [ -n "$opt" ]; do
      case $opt in
        ( d )		next=-d ;;
        ( d?* ) 	set -- "$@" -d "$(map_dates "${opt#d}")"; break ;;
        ( f )		next=-f ;;
        ( f?* ) 	set -- "$@" -f "$(map_dates "${opt#f}")"; break ;;
        ( h* )		help=1 ;;
        ( [rs] )	next=-"$opt" ;;
        ( [Ir]* )	set -- "$@" "-$opt"; break ;;
        ( R* )		set -- "$@" -R ;;
        ( u* )		set -- "$@" -u; export TZ=UTC ;;
        ( [Vv]* )	version ;;
        ( x )		next=-x ;;
        ( x* )		gdate="${opt#x}"; break ;;
        ( * )		rest="${opt#?}"; set -- "$@" "-${opt%$rest}" ;;
      esac
      opt="${opt#?}"
    done
  else
    case $arg in
      ( +*%*J* ) 	set -- "$@" "$(echo "$arg" |awk -v pid="$pid" '{
          gsub(/(^|[^%])%[ #+-]*[0-9]*(\.[0-9]*)?J/, "&<" pid "<%s%z>"); print
        }')" ;;
      #( +*%*J* ) 	set -- "$@" "$(echo "$arg" |perl -pe \
      #		  "s/(?<!%)(%(?:[ #+-]*\d*(?:\.\d*)?)?J)/\$1<$pid<%s%z>/g")" ;;
      ( [0-9+]* )	set -- "$@" "$arg" ;;
      ( --date )	next=-d ;;
      ( --date=* )	set -- "$@" --date="$(map_dates "${arg#--date=}")" ;;
      ( --debug )	DEBUG=1; set -- "$@" $arg ;;
      ( --exec=?* )	gdate="${arg#*=}"; debug "set gdate='$gdate'" ;;
      ( --exec )	next=-x ;;
      ( --file )	next=-f ;;
      ( --file=* )	set -- "$@" --file="$(map_dates "${arg#--file=}")" ;;
      ( --help )	help=1 ;;
      ( --*help* )	help --long ;;
      ( --long )	long=--long ;;
      ( --rfc-3339 )	next=$arg ;;
      ( --ss-format )	next=$arg ;;
      ( --ss-format=* )	ss_fmt="${arg#*=}" ;;
      ( --utc | --univ* )	export TZ=UTC; set -- "$@" "$arg" ;;
      ( --version )	version ;;
      ( * )		set -- "$@" "$arg" ;;
    esac
  fi
done

case $ss_fmt in
  ( '' )	: "using default openoffice format" ;;
  ( e | excel* | x | xl | xls* | ms* | microsoft* )	xls=2 ;;
  ( m | ma | mac* | 1904* )	xls_mac=1 xls_epoch=126316800 xls=0 ;;
  ( [ol] | ooo | [ol]*office* ) 			xls=0 ;;
  ( * ) echo "${0##*/}: invalid argument '$ss_fmt' for '--ss-format'" >&2
        echo "Valid arguments are:" >&2
        echo "  - 'excel' or 'xls' or 'ms'" >&2
        echo "  - 'mac' or '1904'" >&2
        echo "  - 'libreoffice' or 'openoffice' or 'ooo'" >&2
        echo "Try '${0##*/} --help' for more information." >&2
        exit 2
        ;;
esac

export xls DEBUG xls_mac TZ

if [ -n "$help" ]; then
  help $long
elif [ -z "$tmp" ]; then	# remove the trap if it's not needed
  trap - $trap_codes
fi

if ! "$gdate" -d now >/dev/null 2>&1; then
  we_have() { command -v "$1" >/dev/null 2>&1; }  # true if we have the command
  if [ "$gdate" = date ]; then
    if we_have gdate && gdate -d now >/dev/null 2>&1; then
      gdate=gdate
      debug "We are now set to use \`gdate\` (GNU) rather than \`date\` (?)"
    elif we_have busybox && busybox date -d now >/dev/null 2>&1; then
      bdate() { busybox date "$@"; }
      gdate=bdate
      debug "We are now set to use \`busybox date\` rather than \`date\`"
    fi
  else
    echo "${0##*/}: failed to successfully run \`$gdate -d now\`" >&2
    exit 2
  fi
fi

"$gdate" "$@" |perl -wpe 'use strict;
  my $re =
    qr/(?<!%)%([-_^#]*\d*(?:\.\d*)?[EO]?)?J<'$pid'<(-?\d+)([+-])0?(\d+)(\d\d)>/;
  if (my @d = /$re/) {
    my $sign = ($d[2] eq "+" ? 1 : -1);
    my $J = $d[1]/86400 + 25569 + $sign * ($d[3] + $d[4]/60) / 24;

    if ($ENV{DEBUG}) {
      print STDERR $_ . qq(1="$d[0]" 2="$d[1]" 3="$d[2]" 4="$d[3]" 5="$d[4]"\n)
        . "$d[1]/86400 + 25569 + $sign * ($d[3] + $d[4]/60) / 24 = $J\n";
    }

    # adjust for daylight savings: localtime()[8] = is_dst
    my @now  = localtime();
    my @then = localtime($d[1]);
    $J += ($now[8] - $then[8]) / 24;

    # adjust for Excel bug
    $J-- if $ENV{xls} and $J < 61 and ($ENV{xls} == 2 or $J > 0);

    $J -= 1462 if $ENV{xls_mac};

    # format as specified
    if ($d[0] ne "") {
      $J = sprintf("%".$d[0]."f", $J);
    } else {
      $d[0] = ".6";
      $J = sprintf("%".$d[0]."f", $J);
      $J =~ s/\.?0+$//;
    }

    s/$re/$J/g;
  }
  '