man3/strnlen.3

   1 .\" Copyright (c) Bruno Haible <haible@clisp.cons.org>
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  10 .\" References consulted:
  11 .\"   GNU glibc-2 source code and manual
  12 .\"
  13 .TH STRNLEN 3  2015-03-02 "GNU" "Linux Programmer's Manual"
  14 .SH NAME
  15 strnlen \- determine the length of a fixed-size string
  16 .SH SYNOPSIS
  17 .nf
  18 .B #include <string.h>
  19 .sp
  20 .BI "size_t strnlen(const char *" s ", size_t " maxlen );
  21 .fi
  22 .sp
  23 .in -4n
  24 Feature Test Macro Requirements for glibc (see
  25 .BR feature_test_macros (7)):
  26 .in
  27 .sp
  28 .BR strnlen ():
  29 .PD 0
  30 .ad l
  31 .RS 4
  32 .TP 4
  33 Since glibc 2.10:
  34 _XOPEN_SOURCE\ >=\ 700 || _POSIX_C_SOURCE\ >=\ 200809L
  35 .TP
  36 Before glibc 2.10:
  37 _GNU_SOURCE
  38 .RE
  39 .ad
  40 .PD
  41 .SH DESCRIPTION
  42 The
  43 .BR strnlen ()
  44 function returns the number of characters in the string
  45 pointed to by
  46 .IR s ,
  47 excluding the terminating null byte (\(aq\\0\(aq),
  48 but at most
  49 .IR maxlen .
  50 In doing this,
  51 .BR strnlen ()
  52 looks only at the first
  53 .I maxlen
  54 characters in the string pointed to by
  55 .I s
  56 and never beyond
  57 .IR s+maxlen .
  58 .SH RETURN VALUE
  59 The
  60 .BR strnlen ()
  61 function returns
  62 .IR strlen(s) ,
  63 if that is less than
  64 .IR maxlen ,
  65 or
  66 .I maxlen
  67 if there is no null terminating (\(aq\\0\(aq) among the first
  68 .I maxlen
  69 characters pointed to by
  70 .IR s .
  71 .SH ATTRIBUTES
  72 For an explanation of the terms used in this section, see
  73 .BR attributes (7).
  74 .TS
  75 allbox;
  76 lb lb lb
  77 l l l.
  78 Interface       Attribute       Value
  79 T{
  80 .BR strnlen ()
  81 T}      Thread safety   MT-Safe
  82 .TE
  83 .SH CONFORMING TO
  84 POSIX.1-2008.
  85 .SH SEE ALSO
  86 .BR strlen (3)