tangetools/T/T

#!/bin/bash

: <<=cut
=encoding utf8

=head1 NAME

T - make temporary files


=head1 SYNOPSIS

B<T> [I<-#>] [I<filename>]


=head1 DESCRIPTION

B<T> can be used in 3 ways.

=head2 End of a pipe - save to file

If placed last in a pipe B<T> will take standard output from a command
and save it in a temporary file.

Equivalent to: B<cat> >B<tempfile>

=head3 Example

  cat file | T

=head2 Start of a pipe - type the file

If placed first in a pipe B<T> will type the last temporary file's
contents to standard output.

Equivalent to: B<cat tempfile>

=head3 Example

  T | cat 

=head2 In the middle of a pipe - save and type the file

If placed in the middle of a pipe B<T> will copy standard output from
a command and save it in a temporary file and pass the standard output
on.

Equivalent to: B<tee tempfile>

=head3 Example

  cat | T | cat

=head2 Relative .tmp dir

B<T> will use B<$HOME/.tmp> if it cannot find a dir called B<.tmp> in
any of the (grand*)parent dirs.


=head1 OPTIONS

=over 9

=item I<filename>

If given a filename B<T> saves info to that file in the .tmp-directory
instead of tempfile

=item -#

If given option -# which # is a number T will use the #'th last
version.

=back

=head1 FILES

=over 5

=item .tmp/tempfile or .tmp/I<filename>

the most recent temporary file created

=item .tmp/I<filename>-I<YYYY-MM-DD.hh:mm:ss-pid>

the temporary file created at I<YYYY-MM-DD hh:mm:ss> with process id I<pid>

=back


=head1 AUTHOR

Copyright (C) 2017 Ole Tange,
http://ole.tange.dk and Free Software Foundation, Inc.


=head1 LICENSE

Copyright (C) 2012 Free Software Foundation, Inc.

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/>.


=head1 SEE ALSO

B<tee>(1), B<cat>(1)


=cut

find_tmp_dir() {
    dir="$1"
    if [ -d "$1"/.tmp ] ; then
	echo "$1"/.tmp
	return 0
    else
	if [ "/" == $(readlink -f "$dir") ]; then
	    echo $HOME/.tmp
	    return 0
	fi
	find_tmp_dir "../$dir"
	return $?
    fi
}

tmpdir="$(find_tmp_dir .)"
mkdir -p "$tmpdir"

T_DIR="$tmpdir"

#DEBUG_LOG=/tmp/T-debug
DEBUG_LOG=/dev/null

if echo $1 | egrep '^-[0-9]+$' >/dev/null; then
  T_BACK_NO=$(echo $1 | sed -e 's:-::')
  shift
  if [ -z "$1" ]; then
    # No filename given. Default = tempfile
    T_NO_SLASH=tempfile
  else
    # Map / to __ to avoid creating dirs in ~/.tmp
    T_NO_SLASH=$(echo $1 | sed -e 's:/:__:g')
  fi
  T_TEMPFIL=$T_DIR/$T_NO_SLASH
  T_BACK_FILENAME=$(find $T_DIR -name "$T_NO_SLASH"-'[0-9][0-9][0-9][0-9]-[0-9][0-9]-[0-9][0-9].[0-9][0-9]:[0-9][0-9]:[0-9][0-9]-[0-9]*' \
  | sort | tail -n $T_BACK_NO | head -n 1)
  if [ -z "$T_BACK_FILENAME" ]; then
    T_TEMPFIL=$T_DIR/$T_NO_SLASH
  else
    T_TEMPFIL=$T_BACK_FILENAME
  fi
else
  if [ -z "$1" ]; then
    # No filename given. Default = tempfile
    T_TEMPFIL=$T_DIR/tempfile
  else
    # Map / to __ to avoid creating dirs in ~/.tmp
    T_NO_SLASH=$(echo $1 | sed -e 's:/:__:g')
    T_TEMPFIL=$T_DIR/$T_NO_SLASH
  fi
fi


T_NY_FIL="$T_TEMPFIL"-`date +"%Y-%m-%d.%H:%M:%S"`-$$

mkdir $T_DIR 2>/dev/null

if tty -s ; then
  # STDIN is terminal
  # Don't care what STDOUT is
  # T | cat         => T= cat file
  # T               => T= cat file
  echo cat "$T_TEMPFIL" >> $DEBUG_LOG
  cat "$T_TEMPFIL"
else
  # STDIN redir'ed

  if [ -t 1 ] ; then
    # STDOUT = terminal
    # cat | T       => T= >file
    echo cat '>' "$T_NY_FIL" >> $DEBUG_LOG
    cat > "$T_NY_FIL"
  else
    # STDOUT redir'ed
    # cat | T | cat => T= tee file
    echo tee "$T_NY_FIL" >> $DEBUG_LOG
    tee "$T_NY_FIL"
  fi

  # Remove hardlink to most recent file
  rm "$T_TEMPFIL" 2> /dev/null

  # make a hardlink to the most recent file
  ln "$T_NY_FIL" "$T_TEMPFIL"
fi