Bash Script Commands Not Working in Cron

Why does my bash script work in a terminal, but not when using crontab?

The user name precedes the command to run in the system crontab. Use

0 * * * * root /bin/bash /home/henry/yupdate.sh > /dev/null 2>&1

instead.

Cron doesn't accept bash syntax

Thanks to the help of the people here I found my issue was not syntax but rather the use of sh over bash. This was fixed by setting the crontab this way so future users can see:

# m h  dom mon dow   command
SHELL=/bin/bash
@reboot cd /home/ubuntu/waste-cloud-computing/probe && ./probe.sh >> /var/log/somelogfile.log 2>&1

The key points are the SHELL variable being set and the ./ before running the script.

cronjob does not execute a script that works fine standalone

As seen in comments, the problem is that you are not defining what program should be used to execute the script. Take into account that a cronjob is executed in a tiny environment; there, not much can be assumed. This is why we define full paths, etc.

So you need to say something like:

1 * * * * /bin/sh /var/www/html/dbsync/dbsync.sh /var/www/html/dbsync
#         ^^^^^^^

/bin/sh being the binary you want to use to execute the script.

Otherwise, you can set execution permissions to the script and add a shell-script header telling it what interpreter to use:

#!/bin/sh

If you do this, adding the path of the binary is not necessary.

From Troubleshooting common issues with cron jobs:

Using relative paths. If your cron job is executing a script of some
kind, you must be sure to use only absolute paths inside that script.
For example, if your script is located at /path/to/script.phpand
you're trying to open a file called file.php in the same directory,
you cannot use a relative path such as fopen(file.php). The file must
be called from its absolute path, like this: fopen(/path/to/file.php).
This is because cron jobs do not necessarily run from the directory in
which the script is located, so all paths must be called specifically.

Also, I understand you want to run this every minute. If so, 1 * * * * won't do. Intead, it will run at every 1st minute past every hour. So if you want to run it every minute, say * * * * *.