CODEWITHSUNDEEP
c
asdfasdfasdf
asdfasdfasdf

Reputation: 29

how to assign argc and argv to global variables?

Basically I want to pass main's argc and *argv[] to global variables, but am getting:

error: args has an incomplete type char *[];

code:

int argi;
char *args[];

int main(int argc, char *argv[]){
    argi = argc;
    args = argv;
    // blah bah blah
}

int foo(){
    printf("argv[0]: %s\n", args[0]);
    // ayy what it is.
}

Note: for some reason, I don't want to do foo(int argc, char *argv[]) and then in main calling it as foo(argc, argv);

So precisely said, I need to assign main's argc and argv to my global variables.

Upvotes: 0

Views: 1801

Answers (2)

Holloway Kean Ho
Holloway Kean Ho

Reputation: 41

There is 1 problem:

  1. The argv array type is quite restrictive when it comes to managing program parameters.

Hence, the best practice is always about using the pointer of the argv arguments array without altering its data structure: the char **argv.

This way, you can easily transfer or use the array in your source codes.

Here is a quick example (tested with gcc, amd64, on Debian OS) derived from your code snippets:

#include <stdio.h>

int argi;
char **args;

int foo(void) {
    int i;

    for (i=0; i<argi; i++) {
        printf("argv[%d]: %s\n", i, args[i]);
    }
    printf("\n");
    return 0;
}

int main(int argc, char **argv) {
    argi = argc;
    args = argv;
    return foo();
}

If you compile and run, you should get the following:

u0:demo$ ./a.out 
argv[0]: ./a.out

u0:demo$ ./a.out one
argv[0]: ./a.out
argv[1]: one

u0:demo$ ./a.out one two
argv[0]: ./a.out
argv[1]: one
argv[2]: two

u0:demo$ ./a.out one two three
argv[0]: ./a.out
argv[1]: one
argv[2]: two
argv[3]: three

u0:demo$

UPDATE

Fri Apr 19 16:46:05 +08 2019:

  • removed the "string pointer" problem as it was invalid since the string pointer string pointer is represented by char *variable, not char *variable[].

Upvotes: 0

Joseph Sible-Reinstate Monica
Joseph Sible-Reinstate Monica

Reputation: 48672

Arrays and pointers aren't perfectly equivalent, even though they often appear to be convertible. Use char **argv instead of char *argv[] (and the same for the global), and this will then work.

Upvotes: 2

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