strcasecmp, strncasecmp - compare two strings ignoring case
Standard C library (libc, -lc)
#include <strings.h>
int strcasecmp(const char *s1, const char *s2);
int strncasecmp(const char s1[.n], const char s2[.n], size_t n);The strcasecmp() function performs a byte-by-byte
comparison of the strings s1 and s2, ignoring the case
of the characters. It returns an integer less than, equal to, or greater
than zero if s1 is found, respectively, to be less than, to
match, or be greater than s2.
The strncasecmp() function is similar, except that
it compares no more than n bytes of s1 and
s2.
The strcasecmp() and strncasecmp()
functions return an integer less than, equal to, or greater than zero if
s1 is, after ignoring case, found to be less than, to match, or
be greater than s2, respectively.
For an explanation of the terms used in this section, see attributes(7).
| Interface | Attribute | Value |
strcasecmp(), strncasecmp() |
Thread safety | MT-Safe locale |
POSIX.1-2008.
4.4BSD, POSIX.1-2001.
The strcasecmp() and strncasecmp()
functions first appeared in 4.4BSD, where they were declared in
<string.h>. Thus, for reasons of historical
compatibility, the glibc <string.h> header file also
declares these functions, if the _DEFAULT_SOURCE (or,
in glibc 2.19 and earlier, _BSD_SOURCE) feature test
macro is defined.
The POSIX.1-2008 standard says of these functions:
When the 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.
memcmp(3), strcmp(3), strcoll(3), string(3), strncmp(3), wcscasecmp(3), wcsncasecmp(3)