Automatically Split and Rotate Large Linux Log Files

Linux servers often generate continuous log output that can quickly fill up disk space. This tutorial explains a method to split large log files into manageable pieces, name them with the previous day's date, and safely clear the original log.

Get Yesterday's Date

First, obtain the date for the previous day, which will be used in the split file names: current_date=`date -d "-1 day" "+%Y%m%d"` The format +%Y%m%d produces a string like 20230412.

Split the Log File

Use the split command to divide the log into 60 MB chunks, adding a four‑digit numeric suffix:

split -b 65535000 -d -a 4 /home/alvin/myout.txt /home/alvin/log/log_${current_date}_

Parameters: -b 65535000 – split size of 60 MB (bytes). -d -a 4 – use numeric suffixes of length 4 (e.g., 0000, 0001).

The output files will be named like log_20230411_0000, log_20230411_0001, etc.

Truncate the Original Log

After splitting, clear the original log (e.g., nohup.out) to prevent further disk consumption:

cat /dev/null > nohup.out

Full Bash Script

Combine the steps into a single script that can be scheduled to run daily (e.g., via cron):

#!/bin/bash

current_date=`date -d "-1 day" "+%Y%m%d"`
split -b 65535000 -d -a 4 /home/alvin/myout.txt /home/alvin/log/log_${current_date}_
cat /dev/null > nohup.out

Running this script each day will produce date‑stamped log fragments and free up space by truncating the original log file.