strpbrk

strpbrk is a function in the C standard library that searches a string for the first occurrence of any character from a specified set. It is declared in string.h with the prototype: char *strpbrk(const char *s, const char *accept);

The function scans the string s from the start and returns a pointer to the first character in s that matches any character in accept. If no match is found, it returns NULL. The search is performed left to right and does not modify either input string. If accept is an empty string or if s is empty, the result is NULL. If either s or accept is a null pointer, the behavior is undefined.

A common use of strpbrk is to locate delimiter characters in a string, for example to identify where to split input that may contain multiple possible separators. The function returns a pointer into the original string, not a new copy, which can then be used to navigate or modify the string as needed. As a related concept, strcspn computes the length of the initial segment of s that contains none of the characters in accept, which can be used to determine the position of the first delimiter, though it returns a length rather than a pointer.

Strpbrk is part of the ISO C standard library and is widely available on platforms with a conforming C library. It is useful for simple, character-set-based searches without iterating manually over characters.