Bash - How to Send stdout & stderr To a Logfile

Debugging CRON jobs can be quite difficult - there is no visible output, so you don't know if the script failed to run or if the script ran but failed. If it's the latter (ran and failed), you don't get to see any error messages.

If the script is a PHP script, I usually include a standard debug function which allows me to record various checkpoints within the script. These may take the form of comments such as 'Reached point x of the script', or contents of variables eg 'Variable $x contains "abcde12345" '.

However, if the script is a Bash script, you can send the content of stdout and stderr to a logfile. In fact, you can send both outputs to separate files if you wish.

stdout is any output that would normally be sent to the screen in a PuTTY window when a command is run. stderr is any error message generated if there is a problem with the command.

Here is the syntax to use:

Send stdout to a logfile (instead of the terminal):

To append stdout to a logfile use:

To send stdout and stderr to the same logfile:

To send stdout and stderr to different log files use: