How to Follow a Log File Live in Linux

Follow new log entries with tail and handle log rotation correctly.

Short answer

$ tail -f /var/log/app.log

Prints new lines as they are appended. Press Ctrl+C to stop following.

When debugging a running service, repeatedly reopening a log wastes time. `tail -f` keeps the file open and displays new lines as they arrive.

Step by step

$ tail -f app.log

Prints existing final lines and waits for new output.

$ tail -n 100 -f app.log

Shows the last 100 lines and then continues following.

$ tail -F app.log

The capital F keeps trying to reopen the pathname if the underlying file is replaced during log rotation.

$ tail -f app.log | grep --line-buffered -i error

Shows only matching new lines while preserving immediate output.

Use Ctrl+C to stop.
Use `journalctl -f -u SERVICE` for systemd-managed services instead of following a raw journal file.
If tail -f appears stuck, verify that the application is writing to the file you are watching.

It follows a file and prints new data as it is appended.

It follows the pathname and can reopen the file after rotation or replacement.

Pipe tail into grep with `--line-buffered` so matches are displayed promptly.

Print the first or last lines of a file — including live log following with tail -f.

Query the system journal: by service, time window, priority — and follow live.

Find lines matching a pattern in files or piped input — the workhorse of text search.

See how much space is left, and find out what is using it.

Unpack tar.gz, tar.bz2, tar.xz and zip archives from the command line.

Find which process holds a port and stop it cleanly.

Replace text in one file or across a whole project, safely.