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.
SEE ALSO
bstring(3C), malloc(3C), string(3C)
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