1.\" Copyright (c) 1990, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" Chris Torek and the American National Standards Committee X3, 6.\" on Information Processing Systems. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.Dd April 3, 2022 33.Dt STRLEN 3 34.Os 35.Sh NAME 36.Nm strlen , 37.Nm strnlen 38.Nd find length of string 39.Sh LIBRARY 40.Lb libc 41.Sh SYNOPSIS 42.In 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 51computes the length of the string 52.Fa s . 53The 54.Fn strnlen 55function attempts to compute the length of 56.Fa s , 57but never scans beyond the first 58.Fa maxlen 59bytes of 60.Fa s . 61.Sh RETURN VALUES 62The 63.Fn strlen 64function 65returns 66the number of characters that precede the 67terminating 68.Dv NUL 69character. 70The 71.Fn strnlen 72function returns either the same result as 73.Fn strlen 74or 75.Fa maxlen , 76whichever is smaller. 77.Sh SEE ALSO 78.Xr string 3 , 79.Xr wcslen 3 , 80.Xr wcswidth 3 81.Sh STANDARDS 82The 83.Fn strlen 84function 85conforms to 86.St -isoC . 87The 88.Fn strnlen 89function conforms to 90.St -p1003.1-2008 . 91.Sh HISTORY 92The 93.Fn strlen 94function first appeared in the Programmer's Workbench (PWB/UNIX) 95and was ported to 96.At v7 . 97The 98.Fn strnlen 99function first appeared in 100.Fx 8.0 , 101.Ox 4.8 , 102and 103.Nx 6.0 . 104