Section: Linux Programmer's Manual (3)
strcasecmp, strncasecmp - compare two strings ignoring case
int strcasecmp(const char *s1, const char *s2);
int strncasecmp(const char *s1, const char *s2, size_t n);
function performs a byte-by-byte comparison of the strings
ignoring the case of the characters.
It returns an integer
less than, equal to, or greater than zero if
respectively, to be less than, to match, or be greater than
function is similar, except that it compares
no more than
an integer less than, equal to, or greater than zero if
is, after ignoring case, found to be
less than, to match, or be greater than
For an explanation of the terms used in this section, see
||Thread safety||MT-Safe locale|
4.4BSD, POSIX.1-2001, POSIX.1-2008.
functions first appeared in 4.4BSD, where they were declared in
Thus, for reasons of historical compatibility, the glibc
header file also declares these functions, if the
(or, in glibc 2.19 and earlier,
feature test macro is defined.
The POSIX.1-2008 standard says of these functions:
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.
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