INDEX(3C) Standard C Library Functions INDEX(3C)

NAME

index, rindex - string operations

SYNOPSIS

#include <strings.h>

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


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

DESCRIPTION

The index() and rindex() functions operate on null-terminated
strings.


The index() function returns a pointer to the first occurrence of
character c in string s.


The rindex() function 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.

USAGE

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 use a pointer that points to an explicit null string. On some
machines and with some implementations of the C programming language,
a null pointer, if dereferenced, would yield a null string. Though
often used, this practice is not always portable. 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.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+

SEE ALSO

bstring(3C), malloc(3C), string(3C), attributes(7), standards(7)

July 24, 2002 INDEX(3C)