.\"	$OpenBSD: strlen.3,v 1.12 2013/07/17 05:42:11 schwarze Exp $
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.Dd $Mdocdate: July 17 2013 $
.Dt STRLEN 3
.Os
.Sh NAME
.Nm strlen ,
.Nm strnlen
.Nd find length of a string
.Sh SYNOPSIS
.In 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 ,
.Xr wcslen 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 the Programmer's Workbench (PWB/UNIX)
and was ported to
.At v7 .
The
.Fn strnlen
function appeared in glibc 2.0
and was reimplemented for
.Ox 4.8 .