Web - Server

Hi guys
I need help i’m stuck at Command Injection challenge
i was able to bypass the filter and inject my commands , the flag is within the Index.php and i should read to source code of this file to get it, what command should i use to print or display the source code ?

I managed to get to the source code of index.php, but it doesn’t help! there’s no flag in the file!
I don’t know if I can share with you how it’s done or what I got back from the file, but as a hint the php file takes the input from that input field and runs
a command on the server to ping to IP you provided..

you can grep flag from file