passing command line argument from main function to user define C function

Question

i need to pass command line argument from main function (main ) to user defined function called (GetFile) : i tried this:

Main function:

FILE *GetFile(String Extension, String RW);

int main(int argc, char** argv) 
{
File *p
char *rootName = argv[1];
p= GetFile( ".name", "r");
if (p)
{   Do some Stuff!! }
 return 0;
}

User Defined function :

FILE *GetFile(String Extension, String RW)   
{
char  Fn[512];  
strcpy(Fn, rootName);
strcat(Fn, Extension);
return fopen(Fn, RW);
}

User defined function takes rootname file from Main function.copy it and concatenate with the extension passed by calling function

How do i pass the value of rootName value to GetFile function outside my main function.Any help is appreciated

Answer 1

Continuing from the comments, you must be close. Here is an example with the function declaration and definition cleaned up into a working example:

#include <stdio.h>
#include <string.h>

FILE *getfile (char *rn, char *ext, char *rw);

int main (int argc, char **argv) 
{
    FILE *p;
    char *rootname = argc > 1 ? argv[1] : "somefile";

    p = getfile (rootname, ".name", "r");
    if (p)
        printf ("file open for reading!\n");
    else
        fprintf (stderr, "error: file open failed.\n");

    return 0;
}

FILE *getfile (char *rn, char *ext, char *rw)   
{
    char fn[512] = "";

    if (!rn || !*rn || !ext || !*ext || (*rw != 'r' && *rw != 'w')) {
        fprintf (stderr, "getfile() error: invalid parameter.\n");
        return NULL;
    }

    strcpy (fn, rn);
    strcat (fn, ext);

    printf ("opening: %s, filemode: %s\n", fn, rw);

    return fopen (fn, rw);
}

Example File

$ touch myfile.name

Example Use/Output

$ ./bin/fileopenfn myfile
opening: myfile.name, filemode: r
file open for reading!

Example with Unmatched Filename

$ ./bin/fileopenfn
opening: somefile.name, filemode: r
error: file open failed.

Look things over and let me know if you have further questions.

Note: While not an error, the standard coding style for C avoids the use of caMelCase or MixedCase variable names in favor of all lower-case while reserving upper-case names for use with macros and constants. It is a matter of style -- so it is completely up to you. See eg NASA - C Style Guide, 1994