Bash Log Rotation - Mac OSX

log_rotation.sh

#! /bin/bash

##
# Log rotation script
#
# Author: Jordan Gardner (jordanthomasg@gmail.com)
# Version: 1.0
# Last Revision: 12/11/2015
#
# Copyright (c) 2015 Jordan Gardner
#
# Permission is hereby granted, free of charge, to any person obtaining a
# copy of this software and associated documentation files (the "Software"),
# to deal in the Software without restriction, including without limitation
# the rights to use, copy, modify, merge, publish, distribute, sublicense,
# and/or sell copies of the Software, and to permit persons to whom the
# Software is furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included
# in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.

##
# Script Variables
LOG_DIR="/path/to/logs"   # Log directory
LOG_FILE="backup.log"     # Log filename to rotate (MUST CONTAIN ONE AND ONLY ONE `.`)
MAX_SIZE="50000"          # Threshold filesize (in bytes)
MAX_LOGS="0"              # Max number of logs to keep - zero is unlimited

##
# Rotate Logs
cd $LOG_DIR

# Check for an existing $LOG_FILE
if [ -a $LOG_FILE ]; then

  # Check if the logs need rotating
  if [ $( stat -f%z $LOG_FILE ) -ge $MAX_SIZE ]; then

    # Get the count of files
    FILE_COUNT=$(( $( ls -1 | wc -l ) )) # doing some fun embedding to strip the $FILE_COUNT of all whitespace

    # Rotate the log files
    for LOG in $( ls -1 | sort -rn -t. -k3 ); do

        # Check for $MAX_LOGS
        if [ $MAX_LOGS -ne 0 ] && [ $FILE_COUNT -gt $MAX_LOGS ]; then

          # Remove the log file
          rm $LOG

        else

          # Set new filename
          RENAME="$LOG_FILE.$FILE_COUNT"
          
          # Check file extension
          EXT="${LOG##*.}"

          if [ $EXT == "gz" ]; then

            # Just rename already gzipped files
            mv $LOG "$RENAME.gz"

          else

            # Rename the log file
            mv $LOG $RENAME
            # Gzip all log files except $LOG.1
            if [ $FILE_COUNT -ne 1 ]; then
              gzip "$RENAME"
            fi

          fi

        fi

        # Reduce the $FILE_COUNT
        let "FILE_COUNT -= 1"

    done

    # Create new log when finished rotating
    touch $LOG_FILE

  fi

else

  # Create new log if no logs exist
  touch $LOG_FILE

fi