cron stop sending error mails if command output is redirected to logfile - linux

Question

I have a problem with the error mail's from cron
If I create two job's executing the same perl script one which redirected to /dev/null or a logfile and one without redirect I only get an error mail for the one without redirect
/etc/cron.d/test-cron
MAILTO="logs#example.com"
* * * * * root /root/test.sh > /dev/null
* * * * * root /root/test.sh
/root/test.sh
#!/usr/bin/perl
use strict;
print "test\n";
exit 1;
syslog output for cron and postfix
May 18 19:14:01 cron-master CRON[31428]: (root) CMD ([31436] /root/test.sh)
May 18 19:14:01 cron-master CRON[31428]: (CRON) error (grandchild #31436 failed with exit status 1)
May 18 19:14:01 cron-master CRON[31428]: (root) END ([31436] /root/test.sh)
May 18 19:14:01 cron-master CRON[31429]: (root) CMD ([31439] /root/test.sh > /dev/null)
May 18 19:14:01 cron-master CRON[31429]: (CRON) error (grandchild #31439 failed with exit status 1)
May 18 19:14:01 cron-master CRON[31429]: (root) END ([31439] /root/test.sh > /dev/null)
May 18 19:14:01 cron-master postfix/pickup[28859]: 5537251A9: uid=0 from=<root>
May 18 19:14:01 cron-master postfix/cleanup[30966]: 5537251A9: message-id=<20200518191401.5537251A9#cron-master#example.com>
May 18 19:14:01 cron-master postfix/qmgr[143]: 5537251A9: from=<cron-master#example.com>, size=674, nrcpt=1 (queue active)
May 18 19:14:01 cron-master postfix/smtp[30968]: 5537251A9: to=<logs#example.com>, relay=smtp.example.com[80.50.67.97]:587, delay=0.42, delays=0.02/0/0.32/0.09, dsn=2.0.0, status=sent (250 Requested mail action okay, completed: id=1Ma1oK-1jXP8H2tyW-00W08q)
May 18 19:14:01 cron-master postfix/qmgr[143]: 5537251A9: removed
cron -> 3.0pl1-136ubuntu1
postfix -> 3.4.10-1ubuntu1
OS -> latest Ubuntu 20.04 docker image (ubuntu:focal-20200423)
Docker Endpoint -> /usr/sbin/cron -f -l -L 15

Answer 1

You can use tee command to "fork" standard output.
* * * * * root /root/test.sh | tee -a logfile_name
man tee
tee - read from standard input and write to standard output and files
Synopsis
tee [OPTION]... [FILE]...
Description
Copy standard input to each FILE, and also to standard output.
-a, --append
append to the given FILEs, do not overwrite