#!/bin/bash
# rotatelogs--Rolls logfiles in /var/log for archival purposes and to ensure
#   that the files don't get unmanageably large. This script uses a config
#   file to allow customization of how frequently each log should be rolled.
#   The config file is in 
#     logfilename=duration
#   format, where duration is in days. If, in the config file, an entry is 
#   missing for a particular logfilename, rotatelogs won't rotate the file
#   more frequently than every seven days. If duration is set to zero, the
#   script will ignore that particular set of log files.

setglobal logdir = '"/var/log'"	     # Your logfile directory could vary
setglobal config = ""$logdir/rotatelogs.conf""
setglobal mv = '"/bin/mv'"
setglobal default_duration = '7'     # We'll default to a 7-day rotation schedule.
setglobal count = '0'

setglobal duration = $default_duration

if test ! -f $config  {
  # No config file for this script? We're out. You could also
  #   safely remove this test and simply ignore customizations 
  #   when the config file is missing.
  echo "$0: no config file found. Can't proceed." > !2; exit 1
}

if test ! -w $logdir -o ! -x $logdir  {
  # -w is write permission and –x is execute. You need both to create new
  #   files in a Unix or Linux directory. If you don't have 'em, we fail.
  echo "$0: you don't have the appropriate permissions in $logdir" > !2
  exit 1
}

cd $logdir

# While we'd like to use a standardized set notation like ':digit:' with 
#   the find, many versions of find don't support POSIX character class
#   identifiers--hence [0-9].

# This is a pretty gnarly 'find' statement that's explained in the 
#   prose further in this section. Keep reading if you're curious!

for name in [$[find . -maxdepth 1 -type f -size +0c ! -name '*[0-9]*' \
     ! -name '\.*' ! -name '*conf' -print | sed 's/^\.\///]]
{

  setglobal count = $shExpr(' $count + 1 ')

  # Grab the matching entry from the config file for this particular log file.

  setglobal duration = $[grep "^$(name)=" $config|cut -d= -f2]   

  if test -z $duration  { 
    setglobal duration = $default_duration   # If there' no match, use the default value.
  } elif test $duration = "0"  {
    echo "Duration set to zero: skipping $name"
    continue
  }

  # Set up the rotation filenames. Easy enough:

  setglobal back1 = ""$(name).1""; setglobal back2 = ""$(name).2"";
  setglobal back3 = ""$(name).3""; setglobal back4 = ""$(name).4"";

  # If the most recently rolled log file (back1) has been modified within 
  #   the specific quantum, then it's not time to rotate it. This can be 
  #   found with the "-mtime" modification time test to "find".

  if test -f $back1  {
    if test -z $[find '"'$back1'"' -mtime +$duration -print !2 >/dev/null] 
    {
      echo -n "$name's most recent backup is more recent than $duration "
      echo "days: skipping" ;   continue
    }
  }

  echo "Rotating log $name (using a $duration day schedule)"

  # Rotate, starting with the oldest log, but be careful in case one
  #   or more files simply don't exist yet.

  if test -f $back3  {
    echo "... $back3 -> $back4" ; $mv -f $back3 $back4
  }
  if test -f $back2  {
    echo "... $back2 -> $back3" ; $mv -f $back2 $back3
  }
  if test -f $back1  {
    echo "... $back1 -> $back2" ; $mv -f $back1 $back2
  }
  if test -f $name  {
    echo "... $name -> $back1" ; $mv -f $name $back1
  }
  touch $name
  chmod 0600 $name    # Last step: Change file to rw------- for privacy
}

if test $count -eq 0  {
  echo "Nothing to do: no log files big enough or old enough to rotate"
}

exit 0