strspn, strcspn

Standard C library (libc, -lc)

#include <string.h>

size_t strspn(const char *s, const char *accept);
size_t strcspn(const char *s, const char *reject);

strspn()

The strspn() function calculates the length (in bytes) of the initial segment of s which consists entirely of bytes in accept.

strcspn()

The strcspn() function calculates the length of the initial segment of s which consists entirely of bytes not in reject.

It is equivalent to

(strpbrk(s, reject) ?: strnul(s)) - s
    

The strspn() function returns the number of bytes in the initial segment of s which consist only of bytes from accept.

The strcspn() function returns the number of bytes in the initial segment of s which are not in the string reject.

For an explanation of the terms used in this section, see attributes(7).

C11, POSIX.1-2008.

POSIX.1-2001, C89, SVr4, 4.3BSD.

strchr(3), string(3), strpbrk(3), strsep(3), wcsspn(3)