Standard C Library (libc, -lc)
#include <string.h>
size_t
strspn
(const
char *s, const char
*charset);
The strspn
() function spans the initial part of the
nul-terminated string s as long as the characters from
s occur in string charset.
The strspn
() function returns the number of characters
spanned.
The following call to strspn
() will return 3, since the
first three characters of string s are part of string
charset:
char *s = "foobar";
char *charset = "of";
size_t span;
span = strspn(s, charset);
The strspn
() function conforms to ANSI
X3.159-1989 (“ANSI C89”).