strchr.c

Many C samples. It is a good sample for students to learn C language.

/*  File   : strchr.c
    Author : Richard A. O'Keefe.
    Updated: 20 April 1984
    Defines: strchr(), index()

    strchr(s, c) returns a pointer to the  first  place  in  s  where  c
    occurs,  or  NullS if c does not occur in s. This function is called
    index in V7 and 4.?bsd systems; while not ideal the name is  clearer
    than  strchr,  so index remains in strings.h as a macro.  NB: strchr
    looks for single characters,  not for sets or strings.   To find the
    NUL character which closes s, use strchr(s, '\0') or strend(s).  The
    parameter 'c' is declared 'int' so it will go in a register; if your
    C compiler is happy with register _char_ change it to that.
*/

#include "strings.h"

char *strchr(s, c)
    register _char_ *s;
    register int c;
    {
	for (;;) {
	    if (*s == c) return s;
	    if (!*s++) return NullS;
	}
    }