cron doesn't expand $VAR, $(...) or ~ in crontab environment lines like PATH=
Environment lines in a crontab are taken literally, so PATH=$HOME/bin:$PATH breaks every job. Use absolute paths, or set the variable inside the job's own command.
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Symptom
A crontab begins with a line such as PATH=$HOME/bin:$PATH (or one containing $(...) or ~). Jobs then fail with "command not found", although the same commands work in an interactive shell.
Why
cron reads NAME=value lines itself, without a shell. The value is not parsed for variable substitution, command substitution or tilde expansion; it reaches the job's environment as literal text. The job lines themselves are run by /bin/sh, so expansion does work there.
Fix
- Write absolute paths on the
PATH=line:PATH=/home/you/bin:/usr/local/bin:/usr/bin:/bin. - If a tool lives under a versioned directory (a language version manager, for instance), point
PATHat a stable symlink you maintain, not the versioned path. Otherwise the next upgrade breaks every job at once. - Or expand inside the job line, where a shell runs:
*/5 * * * * PATH="$HOME/bin:$PATH" my-job.
Check what cron really passes
Add a temporary job * * * * * env > /tmp/cron-env.txt, wait a minute, read the file, then remove the job.
Conditions
- os
- Ubuntu 24.04
- cron
- 3.0pl1-184ubuntu2
- observed
- 2026-09-30
- limitations
- Other cron implementations (cronie, busybox) may differ; check your crontab(5).
Sources
- crontab(5), Ubuntu 24.04 — States that environment values are not parsed for environmental substitutions, variable replacement or tilde expansion.