Command-Line Arguments In C

Question

I am using C Programming Language.

I write a simple code for arithmetic operations using command-line arguments, but i have a simple problem. when i open the command-line console from windows to test my program. the multiply operation not worked but the other operations work successfully.

here is my code:

#include <stdio.h>
int main(int argc, char *argv[])
{
    if (argc != 4)
    {
        printf("Error: you must use 4 arguments\n\n");
        return 1;
    }

    int x = argv[1][0] - '0';
    int y = argv[3][0] - '0';
    int z = 0;

    if (strcmp(argv[2], "+") == 0)
        z = x + y;
    else if (strcmp(argv[2], "-") == 0)
        z = x - y;
    else if (strcmp(argv[2], "*") == 0)
        z = x * y;
    else
        z = x / y;
    printf("Result = %d\n\n", z);
    return 0;
}

* (Asterisk) is the wildcard character in command prompt. Try "*" OR \*. — skrtbhtngr, Jun 06 '15 at 16:02
@skrtbhtngr That should have been an actual answer. I'd upvote it. — mtijanic, Jun 06 '15 at 16:12
@skrtbhtngr: the `*` is only expanded as a wildcard on Linux-like systems, and OP is on Windows. (Which is kind of important enough to write with a capital.) — Jongware, Jun 06 '15 at 16:22
Try `if (argv[2][0] == '*') ...` rather than string comparison — pmg, Jun 06 '15 at 16:22
Do not tell us "it did not work" – we can infer as much because we can already guess it doesn't. What does it output? If it prints the line `Error: you must use 4 arguments`, then add a line to your code that outputs *what your program thinks it got instead*. — Jongware, Jun 06 '15 at 16:24
@Jongware: See this : https://technet.microsoft.com/en-us/library/bb490639.aspx — skrtbhtngr, Jun 06 '15 at 16:26
* is speacial because it means something to the command shell. In particular it means - any characters in the file name. If there are spaces around it that would mean - any file. As pradheep suggests below - try with backslash. — fukanchik, Jun 06 '15 at 16:27
@skrtbhtngr: only if you see this: [Is there any way to get the windows cmd shell to expand wildcard paths?](http://superuser.com/a/460609), or (even better) https://msdn.microsoft.com/en-us/library/e1w828yy.aspx: ".. which by default does not expand wildcards into separate strings in the argv string array" — Jongware, Jun 06 '15 at 16:27
@HamadaHosny Do as Jongware suggested. After the error appears (and before you `return 1;`), print `argc` for example. I'd also try printing each item in `argv` to display the arguments that the command interpreter was sending to your program: `fprintf(stderr, "argc: %d\nargv:", argc); while (*argv) fprintf(stderr, "\t%s\n", *argv++);` That will aid in determining whether wildcard expansion is a factor here or not, though it shouldn't be, according to the documentation. — , Jun 06 '15 at 16:41

score 2 · Answer 1 · answered Jun 06 '15 at 16:22

2

Run with astreik

$ ./a.out 1  +  3 
Result = 4 

$ ./a.out 1  \*  3 
Result = 3

answered Jun 06 '15 at 16:22

Pradheep

2,973
21
32

same problem exists. Error: you must use 4 arguments – Hamada Hosny Jun 06 '15 at 16:28
what is the operating system you use? i am using windows 7 – Hamada Hosny Jun 06 '15 at 16:36
what compiler are you using? – skrtbhtngr Jun 06 '15 at 16:40
I am using C-Free Standard. – Hamada Hosny Jun 06 '15 at 16:42

score 1 · Answer 2 · edited Jun 06 '15 at 19:45

1

Try using \* (backslash before the *) when running your program.

edited Jun 06 '15 at 19:45

Dan Getz

7,743
6
29
60

answered Jun 06 '15 at 16:18

Klaus

11
1

Command-Line Arguments In C

2 Answers2