Hi I was wondering what values would argv[1] or argv[2] be, if i failed to provide it with command line arguments
+2
A:
It would be garbage NULL.
Therefore you should always first test the argc (argument count) before trying to access the command line arguments.
See this for more detailed information.
missingfaktor
2010-02-07 03:54:35
This answer is slightly wrong as `argv[1]` wouldn't contain garbage, it would contain `NULL`.
Omnifarious
2010-02-07 04:40:26
@Omnifarious : Corrected. Thanks for pointing.
missingfaktor
2010-02-07 05:29:05
It would be more correct to say "`argv[argc]` will be `NULL`". `argv[1]` would be `NULL` if `argc` is 1 (which is nearly always the case if no parameters are passed to the program in a 'hosted environment', but not guaranteed). Of course, `argv[2]` (which the OP asked about) would be undefined in that case.
Michael Burr
2010-02-07 05:55:27
A:
a segfault if you are lucky, garbage if you aren't.
The only safe way to use argv, is to treat it as an array of argc elements.
for (int ii = 0; ii < argc; ++ii)
{
// safe to use argv[ii];
cout << argv[ii];
}
int ix = somevalue;
if (ix >= 0 && ix < argc)
{
// safe to use argv[ix];
}
Note to Jerry. A segfault is what you get when you de-reference NULL on most architectures.
John Knoeller
2010-02-07 03:58:16
+6
A:
You've gotten an amazing number of incorrect answers to this. With nothing entered on the command line, argv[0] will still normally contain the name of the program, so argc will be 1. argv[argc] will contain a null pointer (always, on every conforming implementation of C or C++). In the C standard that requirement is at the second bullet of §5.1.2.1.1/2. In the C++ standard it's at §3.6.1/2.
Jerry Coffin
2010-02-07 04:08:54
This is a nice detail. but the other answers aren't 'incorrect'. if you de-reference argv[1] you will get garbage or a segfault, the fact that the value is supposed to be null is sort of beside the point. It's just as correct to say that arg[1] 'contains' garbage than it is to say that argv[0] 'contains' the program name.
John Knoeller
2010-02-07 05:57:06