1They have slightly different purposes :-
2
31. exec() is for calling a system command, and perhaps dealing with the
4 output yourself.
52. system() is for executing a system command and immediately displaying
6 the output - presumably text.
73. passthru() is for executing a system command which you wish the raw
8 return from - presumably something binary.
9
10Regardless, I suggest you not use any of them. They all produce highly
11 unportable code.