.\" Copyright (c) 1990, 1991 The Regents of the University of California.
.\" All rights reserved.
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.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek and the American National Standards Committee X3,
.\" on Information Processing Systems.
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.\" modification, are permitted provided that the following conditions
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.\"    may be used to endorse or promote products derived from this software
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.\"	$OpenBSD: strlen.3,v 1.9 2010/05/24 21:27:25 millert Exp $
.\"
.Dd $Mdocdate: May 24 2010 $
.Dt STRLEN 3
.Os
.Sh NAME
.Nm strlen ,
.Nm strnlen
.Nd find length of a string
.Sh SYNOPSIS
.Fd #include <string.h>
.Ft size_t
.Fn strlen "const char *s"
.Ft size_t
.Fn strnlen "const char *s" "size_t maxlen"
.Sh DESCRIPTION
The
.Fn strlen
function computes the length of the string
.Fa s .
.Pp
The
.Fn strnlen
function computes the length of the string
.Fa s ,
up to
.Fa maxlen
characters.
The
.Fn strnlen
function will never attempt to address more than
.Fa maxlen
characters, making it suitable for use with character arrays that are
not guaranteed to be NUL-terminated.
.Sh RETURN VALUES
The
.Fn strlen
function returns the number of characters that precede the terminating
.Tn NUL
character.
.Pp
The
.Fn strnlen
function returns the number of characters that precede the terminating
.Tn NUL
or
.Fa maxlen ,
whichever is smaller.
.Sh SEE ALSO
.Xr string 3
.Sh STANDARDS
The
.Fn strlen
function conforms to
.St -ansiC .
.Pp
The
.Fn strlen
and
.Fn strnlen
functions conform to
.St -p1003.1-2008 .
.Sh HISTORY
The
.Fn strlen
function first appeared in
.At v7 .
The
.Fn strnlen
function first appeared in
.Ox 4.8 .