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Name

index, rindex - string operations

Synopsis

#include <strings.h>

char *index(const char *s, int c);

char *rindex(const char *s, int c);

Description

These functions operate on null-terminated strings.

index() returns a pointer to the first occurrence of character c in string s, and rindex() returns a pointer to the last occurrence of character c in string s. Both index() and rindex() return a null pointer if c does not occur in the string. The null character terminating a string is considered to be part of the string.

See Also

string(3C) , bstring(3C) , malloc(3C)

Notes

On most modern computer systems, you can not use a null pointer to indicate a null string. A null pointer is an error and results in an abort of the program. If you wish to indicate a null string, you must have a pointer that points to an explicit null string. On some implementations of the C language on some machines, a null pointer, if dereferenced, would yield a null string; this highly non-portable trick was used in some programs. Programmers using a null pointer to represent an empty string should be aware of this portability issue; even on machines where dereferencing a null pointer does not cause an abort of the program, it does not necessarily yield a null string.

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