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Full Discussion: Results Of A Variable Into An Array Using C Language
Top Forums Programming Results Of A Variable Into An Array Using C Language Post 302929345 by Corona688 on Friday 19th of December 2014 04:36:37 PM
Old 12-19-2014
C does not change what variables do depending on their type, or do anything for you when you ask it to convert one type to another. At best, it will ball it up and cram it through the mail slot, i.e. take you completely literally rather than doing the extra work you wanted.

So, if you want the string to be split, you're going to have to tell it to split it.

strtok is fairly good at doing that. It breaks strings apart on a list of letters, any letter in the list is considered a separator. (I add \n to remove newlines from the end while its at it.)

Two caveats:
  1. It modifies buf. For example, the line a:b:c:d:e\n would become a\0b\0c\0d\0e\0. So you can't call it on anything you can't modify, i.e. strtok("a:b:c:d:e", ":"); would crash.
  2. It returns pointers to things inside buf. Every time you overwrite buf[], i.e. every time you call fgets(), all the pointers strtok() gave you last time will point anywhere or nowhere.

Code:
int main()
{
        char buf[512];
        FILE *fp=fopen("/etc/passwd", "r");

        while(fgets(fp, 512, stdin) != NULL)
        {
                char *tok[64], ntok=1;

                tok[0]=strtok(buf, ":\n");
                // strtok() will keep returning more strings until
                // it runs out and returns NULL.
                tok[ntok]=strtok(NULL, ":\n"); 

                while(tok[ntok] != NULL) tok[++ntok]=strtok(NULL, ":\n");

                if(strcmp(tok[0], "bigbadwolf") == 0) puts(tok[0]);
        }
        fclose(fp);
}

Last edited by Corona688; 12-19-2014 at 05:48 PM..
These 2 Users Gave Thanks to Corona688 For This Post:
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LEARN ABOUT MOJAVE

wcstok

WCSTOK(3)						   BSD Library Functions Manual 						 WCSTOK(3)

NAME

     wcstok -- split wide-character string into tokens

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <wchar.h>

     wchar_t *
     wcstok(wchar_t *restrict ws1, const wchar_t *restrict ws2, wchar_t **restrict ptr);

DESCRIPTION

     The wcstok() function is used to isolate sequential tokens in a null-terminated wide character string, ws1.  These tokens are separated in
     the string by at least one of the characters in ws2.  The first time that wcstok() is called, ws1 should be specified; subsequent calls,
     wishing to obtain further tokens from the same string, should pass a null pointer instead.  The separator string, ws2, must be supplied each
     time, and may change between calls.  The context pointer, ptr, must be provided on each call.

     The wcstok() function is the wide character counterpart of the strtok_r() function.

RETURN VALUES

     The wcstok() function returns a pointer to the beginning of each subsequent token in the string, after replacing the token itself with a null
     wide character (L'').  When no more tokens remain, a null pointer is returned.

EXAMPLES

     The following code fragment splits a wide character string on ASCII space, tab, and newline characters, writing the resulting tokens to stan-
     dard output:

	   const wchar_t *seps = L" 	
";
	   wchar_t *last, *tok, text[] = L" 
one	two		three  
";

	   for (tok = wcstok(text, seps, &last); tok != NULL;
	       tok = wcstok(NULL, seps, &last))
		   wprintf(L"%ls
", tok);

COMPATIBILITY

     Some early implementations of wcstok() omit the context pointer argument, ptr, and maintain state across calls in a static variable like
     strtok() does.

SEE ALSO

     strtok(3), wcschr(3), wcscspn(3), wcspbrk(3), wcsrchr(3), wcsspn(3)

STANDARDS

     The wcstok() function conforms to ISO/IEC 9899:1999 (``ISO C99'').

BSD
								  October 3, 2002							       BSD
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