How to Install and Configure Mailx on Linux for Log Monitoring and Alerts

The article explains how to set up a Linux server to monitor program logs and automatically send email alerts when specific keywords appear, using the Mailx utility and custom shell scripts.

1. Install Mailx

Extract the source package and compile it:

tar -jxf mailx-12.4.tar.bz2 -C /usr/src/ && cd /usr/src/mailx-12.4/

make install UCBINSTALL=/usr/bin/install

If compilation fails, download the patch mailx-12.4-openssl_1.0.0_build_fix-1.patch, place it in the source directory, and apply it:

patch -p0 < mailx-12.4-openssl_1.0.0_build_fix-1.patch

Re‑run the make command after patching: make install UCBINSTALL=/usr/bin/install Verify the installation:

mailx -V

2. Configure Mailx

Edit /etc/nail.rc and add the following SMTP settings at the end of the file:

set [email protected]
set smtp=smtp.example.com
set smtp-auth-user=your_username
set smtp-auth-password=your_password
set smtp-auth=login

Save the file; the screenshot in the original article shows the edited configuration.

3. Test Email Sending

Send a test message from the command line:

echo 'Email body' | mailx -v -s "Email subject" [email protected]

Successful output confirms that Mailx can send mail through the configured SMTP server.

4. Develop Keyword Monitoring Scripts

Three components are created: CheckLogs.sh – reads a log file, tracks the last processed line, and searches new lines for configured keywords. SendMail.sh – a customizable script that sends an email using Mailx.

A conf directory containing chklist, the keyword configuration file.

On the first run, CheckLogs.sh records the current line count. Subsequent executions read only the newly appended lines; if a keyword such as error is found, the script invokes SendMail.sh to issue an alert.

Testing steps shown in the article include inserting the keyword error into the log, running the script to capture the keyword, testing multiple keywords, and adjusting the monitoring frequency. Screenshots illustrate each test result.

5. Completion

After confirming email functionality and successful keyword detection, the log‑monitoring solution is ready for production use.