cronic - Online in the Cloud

PROGRAM:

NAME

cronic - a shell script to help control the most annoying feature of cron: unwanted
emailed output

SYNOPSIS

cronic [COMMAND]

DESCRIPTION

Cronic is a small shim shell script for wrapping cron jobs so that cron only sends email
when an error has occurred.

Cronic defines an error as any non-trace error output or a non-zero result code.

Cronic filters Bash execution traces (or anything matching PS4) from the error output, so
jobs can be run with execution tracing to aid forensic debugging.

Cronic has no options, it simply executes its arguments.

0 1 * * * cronic backup

With cronic, you can turn on Bash's strict error handling and debug options (exit on
error, unset variable detection and execution tracing) to make sure problems are caught
early.

EXAMPLES

Example cron job:

#!/bin/bash
set -o errexit -o nounset -o xtrace
cp -rp data1 /backup
cp -rp data2 /backup
cp -rp data3 /backup

When an error is detected, Cronic outputs a report listing the result code, error output,
and combined trace and error output. The combined output can help put error messages in
context.

Example email from cron with cronic info:

From: user@example.net (Cron Daemon)
To: user@example.net
Subject: Cron <user@server> cronic backup

Cronic detected failure or error output for the command:
backup

RESULT CODE: 1

ERROR OUTPUT:
cp: data2: Permission denied

STANDARD OUTPUT:

TRACE-ERROR OUTPUT:
+ cp -rp data1 /backup
+ cp -rp data2 /backup
cp: data2: Permission denied

VERSION HISTORY

v3 - Use mktemp -d to avoid race-conditions and security problems.

v2 - Corrected command evaluation, so shell meta-chars are preserved correctly (Thanks to
Frank Wallingford for the fix).

v1 - Initial release.

OTHER TOOLS

Joey Hess has written a simpler perl version of cronic, named chronic. It is available in
Debian as part of moreutils.

Use cronic online using onworks.net services