##### Synopsis

    #include <string.h>
    size_t strcspn(const char *s1, const char *s2);

##### Description

strcspn computes the length of the maximum initial segment of the string pointed to by s1 which consists entirely of characters not from the string pointed to by s2.

strcspn returns the length of the segment.

##### Portability

strcspn conforms to ISO/IEC 9899:1990 (C90) and ISO/IEC 9899:1999 (C99).