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Manual Pages  — INDEX


index – locate character in string



Standard C Library (libc, -lc)


#include <strings.h>

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

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


The index() and rindex() functions have been deprecated in favor of strchr(3) and strrchr(3).

The index() function locates the first occurrence of c (converted to a char) in the string pointed to by s. The terminating null character is considered part of the string; therefore if c is ‘\0’, the functions locate the terminating ‘\0’.

The rindex() function is identical to index(), except it locates the last occurrence of c.


The functions index() and rindex() return a pointer to the located character, or NULL if the character does not appear in the string.


memchr(3), strchr(3), strcspn(3), strpbrk(3), strrchr(3), strsep(3), strspn(3), strstr(3), strtok(3)


The index() and rindex() functions appeared in AT&T v6 . Their prototypes existed previously in <string.h> before they were moved to <strings.h> for IEEE Std 1003.1-2001 ("POSIX.1") compliance. The functions are not specified by IEEE Std 1003.1-2008 ("POSIX.1").

INDEX (3) March 20, 2011

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