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'\" t
.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.\" References consulted:
.\" Linux libc source code
.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\" 386BSD man pages
.\" Modified Sat Jul 24 18:12:45 1993 by Rik Faith (faith@cs.unc.edu)
.TH strcasecmp 3 2023-07-20 "Linux man-pages 6.05.01"
.SH NAME
strcasecmp, strncasecmp \- compare two strings ignoring case
.SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
.SH SYNOPSIS
.nf
.B #include <strings.h>
.PP
.BI "int strcasecmp(const char *" s1 ", const char *" s2 );
.BI "int strncasecmp(const char " s1 [. n "], const char " s2 [. n "], \
size_t " n );
.fi
.SH DESCRIPTION
The
.BR strcasecmp ()
function performs a byte-by-byte comparison of the strings
.I s1
and
.IR s2 ,
ignoring the case of the characters.
It returns an integer
less than, equal to, or greater than zero if
.I s1
is found,
respectively, to be less than, to match, or be greater than
.IR s2 .
.PP
The
.BR strncasecmp ()
function is similar, except that it compares
no more than
.I n
bytes of
.I s1
and
.IR s2 .
.SH RETURN VALUE
The
.BR strcasecmp ()
and
.BR strncasecmp ()
functions return
an integer less than, equal to, or greater than zero if
.I s1
is, after ignoring case, found to be
less than, to match, or be greater than
.IR s2 ,
respectively.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbx lb lb
l l l.
Interface Attribute Value
T{
.na
.nh
.BR strcasecmp (),
.BR strncasecmp ()
T} Thread safety MT-Safe locale
.TE
.sp 1
.SH STANDARDS
POSIX.1-2008.
.SH HISTORY
4.4BSD, POSIX.1-2001.
.PP
The
.BR strcasecmp ()
and
.BR strncasecmp ()
functions first appeared in 4.4BSD, where they were declared in
.IR <string.h> .
Thus, for reasons of historical compatibility, the glibc
.I <string.h>
header file also declares these functions, if the
.B _DEFAULT_SOURCE
(or, in glibc 2.19 and earlier,
.BR _BSD_SOURCE )
feature test macro is defined.
.PP
The POSIX.1-2008 standard says of these functions:
.PP
.RS
When the
.B LC_CTYPE
category of the locale being used is from the POSIX locale,
these functions shall behave as if the strings had been converted
to lowercase and then a byte comparison performed.
Otherwise, the results are unspecified.
.RE
.SH SEE ALSO
.BR memcmp (3),
.BR strcmp (3),
.BR strcoll (3),
.BR string (3),
.BR strncmp (3),
.BR wcscasecmp (3),
.BR wcsncasecmp (3)
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