1. check if $1 ( first argument) is available, if yes assign its value to C_id, if not, assign -1 to C_id.
2. if case one executed successfully. check if $2 ( second argument) is available, if yes assign its value to f_id, if not, assign -1 to f_id.
3. if case 2 executed successfully, compare value if C_id with -1, if its equal to -1, execute the Sintaxis function.
---------- Post updated at 04:02 PM ---------- Previous update was at 03:37 PM ----------
And regarding "&&",
&& and || are the shell construct. which applies the action based on the success or failure of the previous commands.
In the above code,
if "cd" si successful to change i.e exit code is zero. this will execute the command after "&&". if it failed to change dir, the commands after "||" will be executed.