Crontab Edit

Safe crontab editing

crontab overwrites the entire table at once. The crontab form can also silently no-op (exit 0, nothing written) under some sandboxed/restricted shells. Works the same on Linux and macOS. Two rules prevent lost jobs.

1. Back up first

crontab -l > /tmp/crontab.backup.txt 2>/dev/null || echo "(no existing crontab)"

An empty/nonzero result just means the table is empty — that's fine.

2. Install via stdin, then verify by reading back

Pipe the content in on stdin — portable and reliable everywhere. Avoid crontab , and do not trust the exit code; only the read-back proves it worked.

crontab - < /path/to/new_crontab.txt        # install (NOT: crontab file)
crontab -l | wc -l                           # verify: line count matches source
crontab -l                                   # verify: jobs are what you expect

If the read-back is empty or the count is wrong, the install failed — retry the stdin form.

To edit in place without clobbering the rest, round-trip it: crontab -l to a file, edit that file, then reinstall via stdin.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: cmflynn
• Source: cmflynn/crontab-edit
• License: MIT

Install and usage instructions live in the source repository linked above.