man3/strnlen.3

   1 .\" Copyright (c) Bruno Haible <haible@clisp.cons.org>
   2 .\"
   3 .\" This is free documentation; you can redistribute it and/or
   4 .\" modify it under the terms of the GNU General Public License as
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   8 .\" References consulted:
   9 .\"   GNU glibc-2 source code and manual
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  11 .TH STRNLEN 3  2012-05-10 "GNU" "Linux Programmer's Manual"
  12 .SH NAME
  13 strnlen \- determine the length of a fixed-size string
  14 .SH SYNOPSIS
  15 .nf
  16 .B #include <string.h>
  17 .sp
  18 .BI "size_t strnlen(const char *" s ", size_t " maxlen );
  19 .fi
  20 .sp
  21 .in -4n
  22 Feature Test Macro Requirements for glibc (see
  23 .BR feature_test_macros (7)):
  24 .in
  25 .sp
  26 .BR strnlen ():
  27 .PD 0
  28 .ad l
  29 .RS 4
  30 .TP 4
  31 Since glibc 2.10:
  32 _XOPEN_SOURCE\ >=\ 700 || _POSIX_C_SOURCE\ >=\ 200809L
  33 .TP
  34 Before glibc 2.10:
  35 _GNU_SOURCE
  36 .RE
  37 .ad
  38 .PD
  39 .SH DESCRIPTION
  40 The
  41 .BR strnlen ()
  42 function returns the number of bytes in the string
  43 pointed to by \fIs\fP, excluding the terminating null bye (\(aq\\0\(aq),
  44 but at most \fImaxlen\fP.
  45 In doing this,
  46 .BR strnlen ()
  47 looks only at the first
  48 \fImaxlen\fP bytes at \fIs\fP and never beyond \fIs+maxlen\fP.
  49 .SH RETURN VALUE
  50 The
  51 .BR strnlen ()
  52 function returns \fIstrlen(s)\fP, if that is less than
  53 \fImaxlen\fP, or \fImaxlen\fP
  54 if there is no null byte (\(aq\\0\(aq) among the first
  55 \fImaxlen\fP bytes pointed to by \fIs\fP.
  56 .SH CONFORMING TO
  57 POSIX.1-2008.
  58 .SH SEE ALSO
  59 .BR strlen (3)