man3/strnlen.3

   1 '\" t
   2 .\" Copyright (c) Bruno Haible <haible@clisp.cons.org>
   3 .\"
   4 .\" SPDX-License-Identifier: GPL-2.0-or-later
   5 .\"
   6 .\" References consulted:
   7 .\"   GNU glibc-2 source code and manual
   8 .\"
   9 .TH strnlen 3 (date) "Linux man-pages (unreleased)"
  10 .SH NAME
  11 strnlen \- determine the length of a fixed-size string
  12 .SH LIBRARY
  13 Standard C library
  14 .RI ( libc ", " \-lc )
  15 .SH SYNOPSIS
  16 .nf
  17 .B #include <string.h>
  18 .PP
  19 .BI "size_t strnlen(const char " s [. maxlen "], size_t " maxlen );
  20 .fi
  21 .PP
  22 .RS -4
  23 Feature Test Macro Requirements for glibc (see
  24 .BR feature_test_macros (7)):
  25 .RE
  26 .PP
  27 .BR strnlen ():
  28 .nf
  29     Since glibc 2.10:
  30         _POSIX_C_SOURCE >= 200809L
  31     Before glibc 2.10:
  32         _GNU_SOURCE
  33 .fi
  34 .SH DESCRIPTION
  35 The
  36 .BR strnlen ()
  37 function returns the number of bytes in the string
  38 pointed to by
  39 .IR s ,
  40 excluding the terminating null byte (\[aq]\e0\[aq]),
  41 but at most
  42 .IR maxlen .
  43 In doing this,
  44 .BR strnlen ()
  45 looks only at the first
  46 .I maxlen
  47 characters in the string pointed to by
  48 .I s
  49 and never beyond
  50 .IR s[maxlen\-1] .
  51 .SH RETURN VALUE
  52 The
  53 .BR strnlen ()
  54 function returns
  55 .IR strlen(s) ,
  56 if that is less than
  57 .IR maxlen ,
  58 or
  59 .I maxlen
  60 if there is no null terminating (\[aq]\e0\[aq]) among the first
  61 .I maxlen
  62 characters pointed to by
  63 .IR s .
  64 .SH ATTRIBUTES
  65 For an explanation of the terms used in this section, see
  66 .BR attributes (7).
  67 .ad l
  68 .nh
  69 .TS
  70 allbox;
  71 lbx lb lb
  72 l l l.
  73 Interface       Attribute       Value
  74 T{
  75 .BR strnlen ()
  76 T}      Thread safety   MT-Safe
  77 .TE
  78 .hy
  79 .ad
  80 .sp 1
  81 .SH STANDARDS
  82 POSIX.1-2008.
  83 .SH HISTORY
  84 POSIX.1-2008.
  85 .SH SEE ALSO
  86 .BR strlen (3)