log

Run a command every n seconds. See cumulative outputs (one run by line) in terminal and/or write to disk.

log is a barebone alternative to watch, better suited for longitudinal monitoring, logging, etc.

Usage

One file: log, a Bash script.

log [-v] [-n SECONDS] [-o FILE] [-t] [-h] <command>

Exit with Ctrl + C.

-v is a toggle:

• Without it: log writes to <command>.log
• With it: log outputs to terminal (no log)

Use -v -o FILE to both see outputs in the terminal and write to FILE.

Options

Flag	Description
-v	Print output to terminal. If absent, writes to disk.
-n SECONDS	Interval in SECONDS (default: 1).
-o FILE	Log output to FILE (only if -o used).
-t	Prepend each line with Unix timestamp.
-h, --help	Show help message and exit.

Examples

log date  # wait a few seconds
^C        # CTRL+C to 

# after four seconds
cat date.log
Tue Apr 28 14:14:33 UTC 2026
Tue Apr 28 14:14:34 UTC 2026
Tue Apr 28 14:14:35 UTC 2026
Tue Apr 28 14:14:36 UTC 2026

log -v date  # no log to file
Tue Apr 28 14:14:51 UTC 2026
Tue Apr 28 14:14:52 UTC 2026
Tue Apr 28 14:14:53 UTC 2026
Tue Apr 28 14:14:54 UTC 2026
...

log -tv date  # Unix timestamps
[1777386029] Tue Apr 28 14:20:29 UTC 2026
[1777386030] Tue Apr 28 14:20:30 UTC 2026
[1777386031] Tue Apr 28 14:20:31 UTC 2026
[1777386032] Tue Apr 28 14:20:32 UTC 2026
...

Write the output of date with Unix timestamps to both terminal (-v) and to a file of our choice (-o /my/file.log).

log -t -v -o /my/file.log date
[1777386138] Tue Apr 28 14:22:18 UTC 2026
[1777386139] Tue Apr 28 14:22:19 UTC 2026
[1777386140] Tue Apr 28 14:22:20 UTC 2026
[1777386141] Tue Apr 28 14:22:21 UTC 2026
^C

cat /my/file.log
[1777386138] Tue Apr 28 14:22:18 UTC 2026
[1777386139] Tue Apr 28 14:22:19 UTC 2026
[1777386140] Tue Apr 28 14:22:20 UTC 2026
[1777386141] Tue Apr 28 14:22:21 UTC 2026