man3/strcasecmp.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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  25 .\" References consulted:
  26 .\"     Linux libc source code
  27 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  28 .\"     386BSD man pages
  29 .\" Modified Sat Jul 24 18:12:45 1993 by Rik Faith (faith@cs.unc.edu)
  30 .TH STRCASECMP 3  2015-04-19 "" "Linux Programmer's Manual"
  31 .SH NAME
  32 strcasecmp, strncasecmp \- compare two strings ignoring case
  33 .SH SYNOPSIS
  34 .nf
  35 .B #include <strings.h>
  36 .sp
  37 .BI "int strcasecmp(const char *" s1 ", const char *" s2 );
  38 .sp
  39 .BI "int strncasecmp(const char *" s1 ", const char *" s2 ", size_t " n );
  40 .fi
  41 .SH DESCRIPTION
  42 The
  43 .BR strcasecmp ()
  44 function performs a byte-by-byte comparison of the strings
  45 .I s1
  46 and
  47 .IR s2 ,
  48 ignoring the case of the characters.
  49 It returns an integer
  50 less than, equal to, or greater than zero if
  51 .I s1
  52 is found,
  53 respectively, to be less than, to match, or be greater than
  54 .IR s2 .
  55 .PP
  56 The
  57 .BR strncasecmp ()
  58 function is similar, except it compares
  59 only the first
  60 .I n
  61 bytes of
  62 .IR s1 .
  63 .SH RETURN VALUE
  64 The
  65 .BR strcasecmp ()
  66 and
  67 .BR strncasecmp ()
  68 functions return
  69 an integer less than, equal to, or greater than zero if
  70 .I s1
  71 (or the first
  72 .I n
  73 bytes thereof) is found, respectively, to be
  74 less than, to match, or be greater than
  75 .IR s2 .
  76 .SH ATTRIBUTES
  77 For an explanation of the terms used in this section, see
  78 .BR attributes (7).
  79 .TS
  80 allbox;
  81 lbw27 lb lb
  82 l l l.
  83 Interface       Attribute       Value
  84 T{
  85 .BR strcasecmp (),
  86 .BR strncasecmp ()
  87 T}      Thread safety   MT-Safe locale
  88 .TE
  89 .SH CONFORMING TO
  90 4.4BSD, POSIX.1-2001, POSIX.1-2008.
  91 .SH NOTES
  92 The
  93 .BR strcasecmp ()
  94 and
  95 .BR strncasecmp ()
  96 functions first appeared in 4.4BSD, where they were declared in
  97 .IR <string.h> .
  98 Thus, for reasons of historical compatibility, the glibc
  99 .I <string.h>
 100 header file also declares these functions, if the
 101 .B _DEFAULT_SOURCE
 102 (or, in glibc 2.19 and earlier,
 103 .BR _BSD_SOURCE )
 104 feature test macro is defined.
 105
 106 The POSIX.1-2008 standard says of these functions:
 107
 108 .RS
 109 When the
 110 .B LC_CTYPE
 111 category of the locale being used is from the POSIX locale,
 112 these functions shall behave as if the strings had been converted
 113 to lowercase and then a byte comparison performed.
 114 Otherwise, the results are unspecified.
 115 .RE
 116 .SH SEE ALSO
 117 .BR bcmp (3),
 118 .BR memcmp (3),
 119 .BR strcmp (3),
 120 .BR strcoll (3),
 121 .BR string (3),
 122 .BR strncmp (3),
 123 .BR wcscasecmp (3),
 124 .BR wcsncasecmp (3)