I'm assuming cron.php contains list of instructions? Remember that cron itself has standard commands such as copy, "cp" with command extensions, i.e. r for replace etc.
And the correct path name you should use is
/home/cpanel_name/public_html/cron.php
if the file you want to execute is within public_html folder.
/home/cpanel_name/cron.php
if the file is located outside public_html folder.
A simple example to copy a file over, writing over the existing file from location A to B:
cp -rf /home/cpanel_name/public_html/A/filename /home/cpanel_name/B/
Notice that I can copy outside of the public_html because /home/cpanel_name/ is my root directory. The same file name will be preserved and the existing file in location B will be overwritten without confirmation. This can be entered directly to Cron job using Standard method. No need to enter Unix command form.
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