'\" t
.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.\" References consulted:
.\"     Linux libc source code
.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\"     386BSD man pages
.\" Modified Sat Jul 24 18:02:26 1993 by Rik Faith (faith@cs.unc.edu)
.TH strlen 3 2023-10-31 "Linux man-pages 6.7"
.SH NAME
strlen \- calculate the length of a string
.SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
.SH SYNOPSIS
.nf
.B #include <string.h>
.P
.BI "size_t strlen(const char *" s );
.fi
.SH DESCRIPTION
The
.BR strlen ()
function calculates the length of the string pointed to by
.IR s ,
excluding the terminating null byte (\[aq]\e0\[aq]).
.SH RETURN VALUE
The
.BR strlen ()
function returns the number of bytes in the string pointed to by
.IR s .
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.na
.nh
.BR strlen ()
T}	Thread safety	MT-Safe
.TE
.SH STANDARDS
C11, POSIX.1-2008.
.SH HISTORY
POSIX.1-2001, C89, SVr4, 4.3BSD.
.SH NOTES
In cases where the input buffer may not contain
a terminating null byte,
.BR strnlen (3)
should be used instead.
.SH SEE ALSO
.BR string (3),
.BR strnlen (3),
.BR wcslen (3),
.BR wcsnlen (3)