#!/bin/bash
# $Id: temp,v 0.5 2005/05/01 21:22:49 jpeek Exp $
#
# temp - rename files as backups
# Usage: temp [-v] name [names...]
#
# This script renames one or more files in the same way that
# the GNU utilities cp(1), mv(1), and ln(1) make backup files.
# For instance, a file foo would be renamed to foo.~1~, foo.~2~,
# or whatever; the script finds the highest-numbered existing
# backup file and renames a file with the next-higher suffix.
#
# We match up to 999 backups.  This limit can be changed by
# adding more patterns to the "for try in" line below and
# be editing the sanity check block "if ((parseB >= 999))".
#
# Written for bash version 2.05 with the hope that it'll be
# upward-compatible.  Notice the #!/bin/bash line above.
# This script uses bash-specific features.

# Placed in the public domain by Jerry Peek, 1 May 2005.
# Use of this script, and any problems you have, is your own
# responsibility.  If you do adapt it, I'd appreciate being
# mentioned.  If you have comments or improvements, please
# send them to me: see http://www.jpeek.com/contact.html.

myname=${0##*/}    # basename of this script (no leading path)

case "$1" in
-v|--verbose)
  vflag=yes
  shift
  ;;
esac

for file
do

  if [[ ! -e $file ]]
  then
    echo "$myname: aborting: can't find '$file'" 1>&2
    exit 1
  fi

  # Find all existing backups of $file.  cp(1) makes a backup with
  # a suffix number one higher than the highest-numbered backup,
  # so we do the same.
  #
  # Set nullglob option so if file* doesn't match, we remove pattern.
  #
  # Using a series of glob patterns like this has the effect of
  # sorting the files numerically by suffix.  It checks for suffix
  # numbers up to 999.  To check higher suffixes, add more patterns.
  # This is a hack but it avoids parsing and piping to sort(1).
  # (Also note the check for 999 in the nested "if" statement below.)
  shopt -s nullglob
  highest=
  for try in $file.~[0-9]~ $file.~[1-9][0-9]~ $file.~[1-9][0-9][0-9]~
  do highest="$try"
  done

  # If we found a backup file, get highest suffix.  Else use 1:
  if [ -n "$highest" ]
  then
    parseA=${highest%*~}  # filename without the last tilde
    parseB=${parseA##*~}  # remove all but the numeric suffix
    if ((parseB >= 999))
    then
      echo "$myname: aborting: won't rename '$file' with suffix above 999." 1>&2
      exit 1
    else
      let suffix=parseB+1
    fi
  else
    suffix=1
  fi

  newname="$file.~$suffix~"

  # Handle -v option:
  test "$vflag" == yes &&
    echo "$myname: renaming '$file' to '$newname'" 1>&2

  # Use -i as a double-check, abort on non-zero return:
  mv -i "$file" "$newname" || exit 1

  # Update timestamp so file won't be removed too soon
  # by a cron job that checks last-modification time:
  touch "$newname"

done