1.\" $OpenBSD: strlen.3,v 1.10 2011/07/25 00:38:53 schwarze Exp $ 2.\" 3.\" Copyright (c) 1990, 1991 The Regents of the University of California. 4.\" All rights reserved. 5.\" 6.\" This code is derived from software contributed to Berkeley by 7.\" Chris Torek and the American National Standards Committee X3, 8.\" on Information Processing Systems. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 3. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.Dd $Mdocdate: July 25 2011 $ 35.Dt STRLEN 3 36.Os 37.Sh NAME 38.Nm strlen , 39.Nm strnlen 40.Nd find length of a string 41.Sh SYNOPSIS 42.Fd #include <string.h> 43.Ft size_t 44.Fn strlen "const char *s" 45.Ft size_t 46.Fn strnlen "const char *s" "size_t maxlen" 47.Sh DESCRIPTION 48The 49.Fn strlen 50function computes the length of the string 51.Fa s . 52.Pp 53The 54.Fn strnlen 55function computes the length of the string 56.Fa s , 57up to 58.Fa maxlen 59characters. 60The 61.Fn strnlen 62function will never attempt to address more than 63.Fa maxlen 64characters, making it suitable for use with character arrays that are 65not guaranteed to be NUL-terminated. 66.Sh RETURN VALUES 67The 68.Fn strlen 69function returns the number of characters that precede the terminating 70.Tn NUL 71character. 72.Pp 73The 74.Fn strnlen 75function returns the number of characters that precede the terminating 76.Tn NUL 77or 78.Fa maxlen , 79whichever is smaller. 80.Sh SEE ALSO 81.Xr string 3 , 82.Xr wcslen 3 83.Sh STANDARDS 84The 85.Fn strlen 86function conforms to 87.St -ansiC . 88.Pp 89The 90.Fn strlen 91and 92.Fn strnlen 93functions conform to 94.St -p1003.1-2008 . 95.Sh HISTORY 96The 97.Fn strlen 98function first appeared in 99.At v7 . 100The 101.Fn strnlen 102function appeared in glibc 2.0 103and was reimplemented for 104.Ox 4.8 . 105