Logging all crontab output using MAILTO

Question

I've been trying to get all cron job outputs to a file (not email). The alias is set in /etc/aliases.

logthecron: "|cronlog.sh"

And in crontab MAILTO=logthecron. The cronlog.sh file writes to output to some file:

#!/bin/sh
$@ 2>&1 | sed -e "s/\(.*\)/[`date`] \1/" >> /tmp/a

I am using sendmail. Sendmail uses smrsh, a restricted shell utility that provides the ability to specify, through the /etc/smrsh directory, an explicit list of executable programs available to Sendmail. So I symlinked cronlog.sh and sendmail to that directory. Something like...

ln -s /root/cron/cronlog.sh /etc/smrsh/

And still keep getting this error.

May 10 09:33:11 sandbox01 smrsh: uid 8: attempt to use "cronlog.sh"
May 10 09:33:11 sandbox01 sendmail[23870]: x4ADXB5Y023868: to="|cronlog.sh", ctladdr=<logthecron@[hostname]> (8/0), delay=00:00:00, xdelay=00:00:00, mailer=prog, pri=30787, dsn=5.0.0, stat=Service unavailable
May 10 09:33:11 sandbox01 sendmail[23870]: x4ADXB5Y023868: x4ADXB5Y023870: DSN: Service unavailable

Note: I am using CentOS v7, the file is executable, email works without issues, tried the entire directory path in the alias and I do not want to write individual cronjob outputs but write all the output of cron jobs to some file.

Reference:

1. smrsh: http://www.faqs.org/docs/securing/chap22sec182.html

2. Logging ALL stderr output of crontab to file

Answer 1

Instead of trying to use MAILTO (which will always be interpreted as an email address), use SHELL.

Set SHELL to the path of a small executable shell script that runs the given command with output directed to a file:

#!/bin/sh

now=$(date)
/bin/sh "$@" 2>&1 | awk -v now="$now" '{ printf("[%s]\t%s\n", now, $0) }' >/tmp/cronjob.log

The "$@" here will be expanded to -c followed by the job specification from the crontab file. It's important to write "$@" with the double quotes.

In the crontab, use

SHELL=/path/to/cronrun

# rest of crontab below...

(assuming /path/to/cronrun is the correct path to that short script)