cron jobs printing to /dev/stdout

Question

I want to setup a job that prints output to /dev/stdout, but cron is intercepting it, and sends an e-mail instead

crontab -l
*/1 * * * * echo "hiccup" >> /dev/stdout 2>&1

this is the message:

21   │ From [email protected]  Tue May 21 11:13:00 2019
22   │ Return-Path: <[email protected]>
23   │ X-Original-To: xxx
24   │ Delivered-To: [email protected]
25   │ Received: by ltus423288.na.yyy.com (Postfix, from userid 501)
26   │     id EE6752E98EF; Tue, 21 May 2019 11:13:00 +0200 (CEST)
27   │ From: [email protected] (Cron Daemon)
28   │ To: [email protected]
29   │ Subject: Cron <xxx@ltus423288> echo "hiccup" >> /dev/stdout 2>&1
30   │ X-Cron-Env: <SHELL=/bin/sh>
31   │ X-Cron-Env: <PATH=/usr/bin:/bin>
32   │ X-Cron-Env: <LOGNAME=xxx>
33   │ X-Cron-Env: <USER=xxx>
34   │ X-Cron-Env: <HOME=/Users/xxx>
35   │ Message-Id: <[email protected]>
36   │ Date: Tue, 21 May 2019 11:13:00 +0200 (CEST)
37   │ Status: O
38   │
39   │ hiccup

I have already configured fluentd that grabs everything from stdout, so I would prefer cron send job logs there. I tried writing to file which is symbolic link to /dev/stdout but it is not working. I am not sure, if I disable sending mails, and order cron to write to /var/log/syslog (and make it symbolic link to /dev/stdout) cron would fail into infinite loop.

Answer 1

The point of cron is to run commands without a terminal. That means there is no terminal to output stdout to. That's why it is being mailed.

You can discard its output:

*/1 * * * * echo "hiccup" >> /dev/null 2>&1

You can pipe the stdout of your jobs to a program, e.g. logger to send it to the syslog daemon:

*/1 * * * * echo "hiccup" | logger -t mycronjob 2>&1

Or redirect it to a file:

*/1 * * * * echo "hiccup" >> /var/tmp/some_file 2>&1

But there simply is no terminal where cron jobs can send their stdout to...

Answer 2

cron works "headless", so /dev/stdout (and anything you echo makes no sense for it). This is why it captures messages and sends mails instead.

However, you can still instruct it to write to any regular file to feed other software. You can do so with output redirection (the > somefile or >> somefile following the launched command), as shown in examples of the accepted answer :

*/1 * * * * echo "hiccup" >> /var/tmp/some_file 2>&1