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  2017-09-15 "" "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 .PP
  37 .BI "int strcasecmp(const char *" s1 ", const char *" s2 );
  38 .PP
  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 that it compares
  59 no more than
  60 .I n
  61 bytes of
  62 .IR s1
  63 and
  64 .IR s2 .
  65 .SH RETURN VALUE
  66 The
  67 .BR strcasecmp ()
  68 and
  69 .BR strncasecmp ()
  70 functions return
  71 an integer less than, equal to, or greater than zero if
  72 .I s1
  73 is, after ignoring case, found to be
  74 less than, to match, or be greater than
  75 .IR s2 ,
  76 respectively.
  77 .SH ATTRIBUTES
  78 For an explanation of the terms used in this section, see
  79 .BR attributes (7).
  80 .TS
  81 allbox;
  82 lbw27 lb lb
  83 l l l.
  84 Interface       Attribute       Value
  85 T{
  86 .BR strcasecmp (),
  87 .BR strncasecmp ()
  88 T}      Thread safety   MT-Safe locale
  89 .TE
  90 .SH CONFORMING TO
  91 4.4BSD, POSIX.1-2001, POSIX.1-2008.
  92 .SH NOTES
  93 The
  94 .BR strcasecmp ()
  95 and
  96 .BR strncasecmp ()
  97 functions first appeared in 4.4BSD, where they were declared in
  98 .IR <string.h> .
  99 Thus, for reasons of historical compatibility, the glibc
 100 .I <string.h>
 101 header file also declares these functions, if the
 102 .B _DEFAULT_SOURCE
 103 (or, in glibc 2.19 and earlier,
 104 .BR _BSD_SOURCE )
 105 feature test macro is defined.
 106 .PP
 107 The POSIX.1-2008 standard says of these functions:
 108 .PP
 109 .RS
 110 When the
 111 .B LC_CTYPE
 112 category of the locale being used is from the POSIX locale,
 113 these functions shall behave as if the strings had been converted
 114 to lowercase and then a byte comparison performed.
 115 Otherwise, the results are unspecified.
 116 .RE
 117 .SH SEE ALSO
 118 .BR bcmp (3),
 119 .BR memcmp (3),
 120 .BR strcmp (3),
 121 .BR strcoll (3),
 122 .BR string (3),
 123 .BR strncmp (3),
 124 .BR wcscasecmp (3),
 125 .BR wcsncasecmp (3)