Shell Programming and Scripting

#!/bin/sh
#----mkbak is a script to backup files
# created by Ygor - dawn/of/time.
# comment & minor edits by 
# [MA]Flying_Meat - couple/minutes/ago.

# echo an error message if no arguments
if [ $# -lt 1 ]
then
   echo "Usage: mkbak filename"
   exit
fi

# assign the current date to "JJJ" (man date)
JJJ=`date '+%j'`

# main loop - walk through the list of files and back 'em up 
while [ $# -gt 0 ]
do
   echo $1
   FILE=$1
   #----check file exists
   if [ ! -f $FILE ]
   then
      echo Error: File '$FILE' not found!!
   else
      # check that hidden directory named ".bkup" exists
      if [ -d .bkup ]
      then
          # give a destination filename to variable "DESTFILE"
          DESTFILE=.bkup/$FILE.$JJJ
      else
          # still give a destination filename, just in current working directory
          DESTFILE=$FILE.$JJJ
      fi

      # duplicate the file
      cp $FILE $DESTFILE
      # compress it with gzip
      gzip -9nf $DESTFILE
      # output the filename
      ls -l $DESTFILE.gz
   fi

   # get the next file name
   shift

# no more filenames to work with. exit main loop
done