#!/bin/bash

# backup--Creates either a full or incremental backup of a set of
#   defined directories on the system. By default, the output 
#   file is compressed and saved in /tmp with a timestamped filename.
#   Otherwise, specify an output device (another disk, a removable 
#   storage device, or whatever else floats your boat).

setglobal compress = '"bzip2'"    # Change to your favorite compression app.
setglobal inclist = ""/tmp/backup.inclist.$[date +%d%m%y]""
 setglobal output = ""/tmp/backup.$[date +%d%m%y].bz2""
 setglobal tsfile = ""$HOME/.backup.timestamp""
  setglobal btype = '"incremental'"  # Default to an incremental backup.
  setglobal noinc = '0'                       # And here's an update of the timestamp.

trap "/bin/rm -f $inclist" EXIT

proc usageQuit
{
  cat << ''' >&2
Usage: $0 [-o output] [-i|-f] [-n]
  -o lets you specify an alternative backup file/device,
  -i is an incremental, -f is a full backup, and -n prevents
  updating the timestamp when an incremental backup is done.
'''
> !2
Usage: $0 [-o output] [-i|-f] [-n]
  -o lets you specify an alternative backup file/device,
  -i is an incremental, -f is a full backup, and -n prevents
  updating the timestamp when an incremental backup is done.
EOF
  exit 1
}

########## Main code section begins here ###########

while getopts "o:ifn" arg {
  match $opt {
    with o  setglobal output = $OPTARG;          # Getopts automatically manages OPTARG.
    with i  setglobal btype = '"incremental'";    
    with f  setglobal btype = '"full'";           
    with n  setglobal noinc = '1';                
    with ?  usageQuit               
  }
}

shift $shExpr(' $OPTIND - 1 ')

echo "Doing $btype backup, saving output to $output"

setglobal timestamp = $[date +'%m%d%I%M]  # Grab month,day,hour,minute from 'date'.
                                 # Curious about date formats? "man strftime"

if test $btype = "incremental"  { 
  if test ! -f $tsfile  {
    echo "Error: can't do an incremental backup: no timestamp file" > !2
    exit 1
  }
  find $HOME -depth -type f -newer $tsfile -user $(USER:-LOGNAME) | \
  pax -w -x tar | $compress > $output
  setglobal failure = "$Status"
} else {
  find $HOME -depth -type f -user $(USER:-LOGNAME) | \
  pax -w -x tar | $compress > $output
  setglobal failure = "$Status"
}

if test $noinc = "0" -a $failure = "0"  {
  touch -t $timestamp $tsfile
}
exit 0