freebsd-dev/lib/libc/string/index.3

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.\" Copyright (c) 1990, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek.
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
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.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" must display the following acknowledgement:
.\" This product includes software developed by the University of
.\" California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" @(#)index.3 8.1 (Berkeley) 6/4/93
1999-08-28 00:22:10 +00:00
.\" $FreeBSD$
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.\"
.Dd June 4, 1993
.Dt INDEX 3
.Os
.Sh NAME
.Nm index , rindex
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.Nd locate character in string
.Sh LIBRARY
.Lb libc
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.Sh SYNOPSIS
.In strings.h
.Ft "char *"
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.Fn index "const char *s" "int c"
.Ft "char *"
.Fn rindex "const char *s" "int c"
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.Sh DESCRIPTION
The
.Fn index
function
locates the first occurrence of
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.Fa c
(converted to a
.Vt char )
in the string pointed to by
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.Fa s .
The terminating null character is considered part of the string;
therefore if
.Fa c
is
.Ql \e0 ,
the functions locate the terminating
.Ql \e0 .
.Pp
The
.Fn rindex
function is identical to
.Fn index ,
except it locates the last occurrence of
.Fa c .
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.Sh RETURN VALUES
The functions
.Fn index
and
.Fn rindex
return a pointer to the located character, or
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.Dv NULL
if the character does not appear in the string.
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.Sh SEE ALSO
.Xr memchr 3 ,
.Xr strchr 3 ,
.Xr strcspn 3 ,
.Xr strpbrk 3 ,
.Xr strrchr 3 ,
.Xr strsep 3 ,
.Xr strspn 3 ,
.Xr strstr 3 ,
.Xr strtok 3
.Sh HISTORY
The
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.Fn index
and
.Fn rindex
functions appeared in
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.At v6 .
Their prototypes existed previously in
.In string.h
before they were moved to
.In strings.h
for
.St -p1003.1-2001
compliance.