This is a very common scenario to log the application messages into a separate file; Here, we will see a Shell script how to write logs in a separate file.

Shell Script How to write logs in a separate file:

To make this use-case simple and more reusable, I am writing two different script files one is to write the messages to the log file, and another one is for generating the logs.

Create log_functions.sh file which will be responsible for logging the different types of log messages like INFO, WARN and ERROR into application.log file.

#!/bin/bash

VAR_LOG_DIR="/home/"
VAR_LOG_FILE="application.log"

logWarn(){
     echo "--[`date "+%Y/%m/%d %H:%M:%S"`] -- WARN -- $@" >> ${VAR_LOG_DIR}/${VAR_LOG_FILE};
}

logInfo(){
     echo "--[`date "+%Y/%m/%d %H:%M:%S"`] -- INFO -- $@" >> ${VAR_LOG_DIR}/${VAR_LOG_FILE};
}

logError(){
     echo "--[`date "+%Y/%m/%d %H:%M:%S"`] -- ERROR -- $@" >> ${VAR_LOG_DIR}/${VAR_LOG_FILE};
     exit 1;
}

Create a simple shell script to write some messages into application.log file.

#!/bin/bash

#Getting current directory
readonly CURRENT_DIR=$(cd `dirname $0`; pwd -P)
source ${CURRENT_DIR}/log_functions.sh

logInfo "I am information"
logWarn " I am a Warning message"
logError "I am an Error"

Make both files as executable.

$chmod 777 log_functions.sh
$chmod 777 log_messages.sh

Run log_messages.sh file and see the application.log file.

$./log_messages.sh

check the application.log file

$ more application.log
--[2020/04/16 15:41:07] -- INFO -- I am information
--[2020/04/16 15:41:07] -- WARN --  I am a Warning message
--[2020/04/16 15:41:07] -- ERROR -- I am an Error

Happy Learning 🙂