Info:tee splits stdout to both terminal and file. 2>&1 redirects stderr into stdout first to capture error logs. -a appends output instead of overwriting.
Examples:
$ ./script.sh 2>&1 | tee output.log # Overwrite log with output + errors
$ make 2>&1 | tee build.log | grep -E 'error|warning' # Log all, filter display
$ sudo apt upgrade 2>&1 | tee -a /var/log/upgrades.log # Append system upgrade log
Note: Without 2>&1, tee only captures standard output and misses error messages. Use tee -a when running repeated scripts to maintain a history.
LinuxTeck.com
linuxteck@ubuntu:~$ ./deploy.sh 2>&1 | tee -a deploy.log
[INFO] Starting deployment process...
[INFO] Pulling latest code updates...
[WARN] Environment variable PORT not set (default: 8080)
[SUCCESS] Deployment completed!
linuxteck@ubuntu:~$ cat deploy.log
[INFO] Starting deployment process...
[INFO] Pulling latest code updates...
[WARN] Environment variable PORT not set (default: 8080)
[SUCCESS] Deployment completed!
linuxteck@ubuntu:~$
John Britto Founder & Chief-Editor @LinuxTeck. A Computer Geek and Linux Intellectual having more than 20+ years of experience in Linux and Open Source technologies.
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