Cron job isn't writing to log file

Question

I have a shell script that writes the date to a log file when executed. When I run the script manually, the correct output gets written to the file. However, this needs to be automated, and when I run as a cron job, nothing is getting written to the file and I am confused why.

crontab:

0 * * * * tomcat /usr/bin/sh /apps/rdsreplication/snap_replication.sh

Sample Code:

#/bin/bash/

echo ---------------------------------------- >> create_snap.txt
echo Start time:  >> create_snap.txt
date >> create_snap.txt

Any help would be appreciated!

Answer 1

The shell script needs to use the full path for the log file:

#/bin/bash/
# assuming you want the txt file in the same directory as the bash script
logfile="$(dirname "$0")/create_snap.txt"
{
    echo ----------------------------------------
    echo Start time:
    date 
} >> "$logfile"

Answer 2

For a user crontab, the man page for crontab(5) describes the fields:

Each line has five time and date fields, followed by a user name if this is the system crontab file, followed by a command.

So in your case, you'd want this:

0 * * * * /usr/bin/sh /apps/rdsreplication/snap_replication.sh

You should be aware that cron will email you the output and stderr from the job (if any), so you probably have quite a lot of emails telling you that cron can't find the command tomcat. (Or if it can, that tomcat doesn't understand the rest of the line.)