Cron Cheatsheet — 80+ Syntax, Expressions, Special Strings, and Crontab Tips

The five-field cron format: minute hour day-of-month month day-of-week command. Each asterisk means "every possible value" for that field.

# ┌─── minute (0-59)

# │ ┌─── hour (0-23)

# │ │ ┌─── day of month (1-31)

# │ │ │ ┌─── month (1-12)

# │ │ │ │ ┌─── day of week (0-7, 0 and 7 = Sunday)

# │ │ │ │ │

# * * * * *  /path/to/command

The minute field accepts integers 0–59. `0` means "at the top of the hour"; `30` means "at the half-hour mark".

0 * * * *  /run/hourly.sh   # at :00 every hour

30 * * * * /run/half.sh     # at :30 every hour

The hour field uses 24-hour format: 0 = midnight, 12 = noon, 17 = 5 pm, 23 = 11 pm. No AM/PM notation.

0 0  * * * cmd   # midnight

0 12 * * * cmd   # noon

0 17 * * * cmd   # 5 pm

Day of the month, 1–31. Not all months have 31 days; cron will simply not run on days that do not exist (e.g. Feb 30 never fires).

0 0 1  * * /monthly-start.sh   # first of month

0 0 15 * * /mid-month.sh       # 15th of month

Month field: 1 = January, 12 = December. Most cron implementations also accept three-letter abbreviations (Jan, Feb, Mar…).

0 0 1 1   * /new-year.sh   # January 1st

0 0 1 Jun * /mid-year.sh   # June 1st

Day of week: 0 and 7 both mean Sunday, 1 = Monday, …, 6 = Saturday. Most cron implementations also accept abbreviations (Sun, Mon, Tue…).

⚠ Gotcha: Both 0 and 7 mean Sunday — a common off-by-one trap coming from languages where weekdays are 0–6. Stick to 0–6 for clarity.

0 0 * * 0 /sunday.sh   # Sunday

0 0 * * 1 /monday.sh   # Monday

0 0 * * 5 /friday.sh   # Friday

Wildcard: matches every valid value for the field. `* * * * *` means "every minute of every hour of every day".

* * * * * /every-minute.sh

* * * * 1-5 /weekday-minutes.sh

Comma-separated list: run at each value in the list. `1,15,30` in the minute field runs at minutes 1, 15, and 30 of every hour.

0 6,12,18 * * * /three-times.sh   # 6 am, noon, 6 pm

0,30 * * * *    /every-half.sh

Dash range: matches all integers from 1 to 5 inclusive. `1-5` in the day-of-week field means Monday through Friday.

0 9 * * 1-5 /weekday.sh   # Mon–Fri at 9 am

0 8-18 * * * /work-hrs.sh

Step value: run every N units starting from the lowest value. `*/5` in the minute field means 0, 5, 10, 15, …, 55. Equivalent to `0-59/5`.

*/5  * * * * /every-5-min.sh

*/15 * * * * /every-quarter.sh

*/30 * * * * /every-half.sh

Range combined with step: matches values in the range at every Nth step. `0-30/10` matches 0, 10, 20, 30 — the first half of the hour at 10-minute intervals.

0-30/10 * * * * /cmd.sh   # at :00, :10, :20, :30 of every hour

Lines starting with `#` are comments and are ignored by the cron daemon. Use them to document what each job does.

# Daily database backup

0 2 * * * /usr/local/bin/backup-db.sh

# Hourly cache purge

0 * * * * /usr/local/bin/clear-cache.sh

Field position reminder: the first `0` is the minute field, the lone `*` is the hour field. This means "at minute 0 of every hour" — i.e., once per hour, on the hour.

0 * * * * /usr/local/bin/hourly-check.sh

Every minute, every hour, every day. The most frequent standard cron schedule — fires 1,440 times per day.

* * * * * /health-check.sh

Every 2 minutes.

*/2 * * * * /poll-queue.sh

Every 5 minutes. One of the most common production schedules for lightweight polling jobs.

*/5 * * * * /check-status.sh

Every 10 minutes.

*/10 * * * * /sync-data.sh

Every 15 minutes (quarter-hour).

*/15 * * * * /refresh-cache.sh

Every 30 minutes (twice per hour). Runs at :00 and :30 of every hour.

*/30 * * * * /half-hourly.sh

Once per hour, at minute 0 (the top of the hour).

0 * * * * /hourly-report.sh

Once per hour, at minute 30 (the half-hour mark).

30 * * * * /half-past.sh

Every 2 hours, on the hour. Runs at 00:00, 02:00, 04:00, …, 22:00.

0 */2 * * * /every-2-hours.sh

Every 4 hours. Runs at 00:00, 04:00, 08:00, 12:00, 16:00, 20:00.

0 */4 * * * /every-4-hours.sh

Every 6 hours. Runs at midnight, 6 am, noon, and 6 pm.

0 */6 * * * /6-hourly.sh

Twice a day: midnight and noon.

0 0,12 * * * /twice-daily.sh

Three times a day: at 8 am, noon, and 5 pm.

0 8,12,17 * * * /three-times-daily.sh

Once a day at midnight (00:00). The most common daily job pattern.

0 0 * * * /daily-cleanup.sh

Once a day at 2 am. Popular for nightly backups — late enough to miss peak traffic, early enough to finish before business hours.

0 2 * * * /backup-db.sh

Once a day at 9 am.

0 9 * * * /morning-report.sh

Once a day at noon (12:00).

0 12 * * * /noon-digest.sh

Every weekday (Monday through Friday) at 9 am. Weekends are skipped entirely.

0 9 * * 1-5 /standup-reminder.sh

Every hour during business hours, Monday through Friday. Runs at 9:00, 10:00, …, 17:00 on weekdays only.

0 9-17 * * 1-5 /business-hours-check.sh

Weeknights at 10 pm — after business hours but before midnight; a common time for nightly builds.

0 22 * * 1-5 /nightly-build.sh

Every Sunday at midnight. Classic weekly maintenance window.

0 0 * * 0 /weekly-report.sh

Every Monday at midnight — start-of-week reset tasks.

0 0 * * 1 /weekly-reset.sh

Every Friday at midnight — end-of-week reporting tasks.

0 0 * * 5 /weekly-digest.sh

Every weekend (Saturday and Sunday) at midnight.

0 0 * * 6,0 /weekend-task.sh

Every Sunday at 4:05 am. The canonical "weekly cron" example from many Linux distributions — offset by 5 minutes to avoid all-at-once stampedes on the hour.

5 4 * * 0 /weekly-maintenance.sh

First day of every month at midnight.

0 0 1 * * /monthly-invoice.sh

First and fifteenth of every month at midnight — a common billing cycle.

0 0 1,15 * * /bimonthly-report.sh

Once a quarter: first day of January, April, July, and October at midnight.

0 0 1 */3 * /quarterly-audit.sh

Once a year on January 1st at midnight. Use @yearly for a more readable equivalent.

0 0 1 1 * /annual-report.sh

Days 28–31 of every month. NOT a reliable "last day of month" — on a 28-day February this runs only on the 28th, while on a 31-day month it runs four times.

⚠ Gotcha: There is no portable "last day of month" syntax in standard cron. Use a wrapper: `[[ $(date -d tomorrow +%d) == 01 ]] && /path/cmd`.

0 0 28-31 * * /maybe-end-of-month.sh

Run the command once, immediately after the cron daemon starts (usually at system boot). Useful for starting user-level services that should survive reboots.

⚠ Gotcha: @reboot jobs run when crond starts, not at a specific boot phase. Services needing the network or mounts to be ready may fail — add a `sleep 10` guard or use systemd instead.

@reboot /home/user/start-app.sh

@reboot sleep 10 && /usr/local/bin/myservice

Run once an hour at the beginning of the hour. Equivalent to `0 * * * * command`.

@hourly /usr/local/bin/clear-tmp.sh

Run once a day at midnight (00:00). `@midnight` is an alias for `@daily`. Equivalent to `0 0 * * * command`.

@daily    /usr/local/bin/rotate-logs.sh

@midnight /usr/local/bin/daily-backup.sh

Run once a week on Sunday at midnight. Equivalent to `0 0 * * 0 command`.

@weekly /usr/local/bin/weekly-report.sh

Run once a month on the first day of the month at midnight. Equivalent to `0 0 1 * * command`.

@monthly /usr/local/bin/monthly-invoice.sh

Run once a year on January 1st at midnight. Both strings are equivalent to `0 0 1 1 * command`.

@yearly   /usr/local/bin/archive-data.sh

@annually /usr/local/bin/annual-cleanup.sh

Set the shell cron uses to execute commands. Default is usually `/bin/sh`. Set to `/bin/bash` if you use bash-specific syntax in your commands.

SHELL=/bin/bash

0 * * * * [[ -f /tmp/flag ]] && echo "found"

Send any output (stdout + stderr) from cron jobs to this email address. Requires a local mail agent (sendmail, postfix, ssmtp) configured on the system.

MAILTO=admin@example.com

0 2 * * * /backup.sh

Disable email output entirely. Any output from jobs is silently discarded. Use this when you redirect output to log files and do not want cron flooding your inbox.

MAILTO=""

0 * * * * /hourly.sh >> /var/log/hourly.log 2>&1

Override the home directory for cron jobs. Affects `~` expansion and defaults for programs that reference $HOME.

HOME=/home/deploy

0 0 * * * ~/.local/bin/cleanup.sh

Set a full PATH for all jobs in the crontab. The default cron PATH is very restricted — typically only `/usr/bin:/bin`. Add this line at the top to make all system commands available.

⚠ Gotcha: Setting PATH in the crontab does NOT source NVM, pyenv, or other version-manager shims. Source those explicitly in the command or a wrapper script.

PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

0 * * * * node /app/cron.js

Set the timezone for all jobs in this crontab file. Jobs run relative to the specified timezone, regardless of the system timezone.

⚠ Gotcha: `CRON_TZ` is supported by Vixie cron and many derivatives. Some systems use `TZ` instead. Check your cron daemon's documentation.

CRON_TZ=America/New_York

0 9 * * * /send-nyc-report.sh

Alternative timezone variable supported by most cron implementations. Use `TZ=UTC` to ensure jobs always run in UTC regardless of the system locale.

TZ=UTC

0 0 * * * /midnight-utc.sh

Manually source login files at the start of a cron command. The cron environment is minimal and does NOT auto-source .bashrc, .profile, or .bash_profile.

⚠ Gotcha: Sourcing .bashrc inside a cron job can cause side effects (interactive-only code, aliases, prompts). Better: set specific env vars in the crontab header.

0 * * * * . /etc/profile; /path/to/script.sh

Open the current user's crontab in $EDITOR for editing. The new version replaces the old one atomically when you save and exit.

crontab -e

EDITOR=nano crontab -e   # use nano instead of vi

List (print to stdout) the current user's crontab without opening an editor.

crontab -l

crontab -l 2>/dev/null || echo "no crontab for $USER"

Remove (delete) the current user's entire crontab. There is NO confirmation prompt and NO undo. Use with extreme caution.

⚠ Gotcha: `crontab -r` wipes the crontab instantly with zero confirmation. Always `crontab -l > backup.cron` before running it, or use `crontab -e` to remove individual lines.

crontab -l > ~/crontab-backup-$(date +%Y%m%d).cron  # backup first!

crontab -r

Edit the crontab for another user (requires root or sudo). The `-u` flag specifies which user's crontab to edit.

sudo crontab -u deploy -e

sudo crontab -u deploy -l   # list deploy user's crontab

Backup the current crontab to a file. Restore it later with `crontab backup.cron` or `cat backup.cron | crontab -`.

crontab -l > ~/crontab-$(date +%Y%m%d).bak

cat ~/crontab-20240101.bak | crontab -   # restore

System-wide cron job directory. Files here must include a username field: `minute hour dom month dow USERNAME command`. Used by packages to install their own cron jobs.

# /etc/cron.d/myapp

0 2 * * * root     /usr/local/bin/myapp-backup.sh

*/5 * * * * www-data /var/www/myapp/cron.php

Drop-in script directories managed by `run-parts`. Place executable scripts (no dot in filename) here and they run daily, weekly, or monthly via anacron or crond.

⚠ Gotcha: Scripts in /etc/cron.daily/ must be executable (`chmod +x`) and must NOT have a dot in the name (`backup.sh` is ignored; use `backup` or `backup_sh`).

chmod +x /etc/cron.daily/backup

run-parts --test /etc/cron.daily/   # dry run

Run `command` only if the lock file is not already held by another instance. If a previous run is still in progress, this invocation exits immediately — preventing job pile-up.

*/5 * * * * flock -n /tmp/sync.lock /usr/local/bin/sync.sh

*/5 * * * * flock -n /tmp/job.lock -c "/path/to/long.sh >> /var/log/job.log 2>&1"

Redirect stdout and stderr to a log file (append mode). Use this instead of relying on MAILTO for job output.

0 2 * * * /backup.sh >> /var/log/backup.log 2>&1

*/5 * * * * /poll.sh >> /var/log/poll.log 2>&1

Suppress all output from a cron job — stdout and stderr both discarded. Use when you trust the job is correct and do not need a log.

*/5 * * * * /health-check.sh > /dev/null 2>&1

0 * * * * /cache-clear.sh >/dev/null 2>&1

Debug the cron environment. Add `env >> /tmp/cron-env.log` to also dump the full environment — compare PATH and vars to your interactive terminal.

* * * * * date >> /tmp/cron-test.log 2>&1

* * * * * env  >> /tmp/cron-env.log  2>&1

* * * * * which node >> /tmp/cron-path.log 2>&1

Run all executable scripts in a directory in alphabetical order. This is the mechanism cron uses for /etc/cron.daily/, /etc/cron.weekly/, etc.

0 2 * * *   run-parts /etc/cron.daily/

0 2 * * 0   run-parts --report /etc/cron.weekly/

Check if the cron daemon is running. Named `cron` on Debian/Ubuntu and `crond` on RHEL/CentOS/Fedora. Use `journalctl -u cron` to inspect recent logs.

systemctl status cron        # Debian/Ubuntu

systemctl status crond       # RHEL/CentOS

journalctl -u cron -n 50     # recent cron logs

The cron daemon runs with a stripped-down PATH (usually only `/usr/bin:/bin`). Commands like `node`, `python`, `docker`, or custom scripts not in those dirs are not found. Fix: use absolute paths or set PATH at the top of the crontab.

# BAD: node is not in /usr/bin:/bin

0 * * * * node /app/cron.js

# GOOD: absolute path

0 * * * * /usr/local/bin/node /app/cron.js

# GOOD: set PATH at top of crontab

PATH=/usr/local/bin:/usr/bin:/bin

0 * * * * node /app/cron.js

An unescaped `%` in a cron command is treated as a newline character — everything after the first `%` is fed to the command as stdin. Escape literal percent signs as `\%`.

# BAD: % in date format treated as newline

0 0 * * * echo $(date +%Y-%m-%d) >> /tmp/log

# GOOD: escape % signs

0 0 * * * echo $(date +\%Y-\%m-\%d) >> /tmp/log

# BETTER: wrap in a script that handles the format

If both day-of-month and day-of-week are set to non-`*` values, cron runs when EITHER condition is true (OR), NOT when both are true (AND). `0 0 1 * 5` runs on the 1st of every month AND every Friday.

⚠ Gotcha: This behavior is mandated by POSIX. Workaround: add a shell guard inside the command — `[ $(date +%u) -eq 5 ] && [ $(date +%d) -eq 01 ] && /cmd`.

# Runs on the 1st of every month AND on every Friday:

0 0 1 * 5 /cmd.sh

# Only on Fridays that are also the 1st:

0 0 1 * 5 [ "$(date +%u)" = "5" ] && /cmd.sh

Cron does NOT source `.bashrc`, `.bash_profile`, or `.profile`. Environment variables, shell functions, and aliases defined there are invisible to cron jobs. Export everything you need directly in the crontab header.

# In .bashrc (NOT visible to cron):

export NVM_DIR="$HOME/.nvm"

# In crontab (visible to cron):

NVM_DIR=/home/user/.nvm

0 * * * * /path/to/node-app.sh

`crontab -r` removes the ENTIRE crontab with no confirmation prompt. Many users accidentally run it thinking it removes one job. Always use `crontab -e` to delete individual lines.

# Always back up first:

crontab -l > ~/crontab-backup.txt

# Use crontab -e to remove specific jobs, NOT crontab -r

`* 0 * * *` runs every minute for the entire midnight hour (00:00, 00:01, …, 00:59) — 60 executions. `0 * * * *` runs once an hour at :00. A common mistake when trying to write "once a day at midnight" (`0 0 * * *`).

* 0 * * * /cmd.sh   # runs 60 times between midnight and 1am!

0 0 * * * /cmd.sh   # once at midnight (correct)

0 * * * * /cmd.sh   # once an hour

Cron uses the system timezone by default. If the server runs in UTC and you expect local time, jobs run at unexpected hours. Set `CRON_TZ=` or `TZ=` in the crontab, or document the timezone assumption clearly.

# System TZ: UTC. Want to run at 9 am Beijing time (UTC+8):

0 1 * * * /morning.sh   # 01:00 UTC = 09:00 CST

# Cleaner with explicit TZ:

CRON_TZ=Asia/Shanghai

0 9 * * * /morning.sh

Cron silently fails (or sends a "Permission denied" email) if the script lacks execute permission. Always `chmod +x` your cron scripts and verify with `ls -l`.

chmod +x /usr/local/bin/my-cron-script.sh

ls -l /usr/local/bin/my-cron-script.sh   # verify -rwxr-xr-x

Relative paths (e.g. `./script.sh` or `../data`) resolve relative to the working directory, which in cron is typically $HOME — not the script's location. Use absolute paths everywhere.

# BAD: relative path may not resolve correctly

0 * * * * ./scripts/cleanup.sh

# GOOD: absolute path

0 * * * * /home/user/scripts/cleanup.sh

In cron, months are 1-indexed (January = 1, December = 12), unlike JavaScript's `Date.getMonth()` which is 0-indexed. Setting month to `0` is invalid in most implementations.

# January 1st:

0 0 1 1 * /new-year.sh    # CORRECT (month 1)

0 0 1 0 * /new-year.sh    # WRONG  (month 0 is invalid)