strcasecmp(3) Library Functions Manual strcasecmp(3)
NAME
strcasecmp, strncasecmp - compare two strings ignoring case
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <strings.h>
int strcasecmp(const char *s1, const char *s2);
int strncasecmp(const char s1[.n], const char s2[.n], size_t n);
DESCRIPTION
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, re-
spectively, 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.
RETURN VALUE
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.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
┌─────────────────────────────────────┬───────────────┬────────────────┐
│ Interface │ Attribute │ Value │
├─────────────────────────────────────┼───────────────┼────────────────┤
│ strcasecmp(), strncasecmp() │ Thread safety │ MT-Safe locale │
└─────────────────────────────────────┴───────────────┴────────────────┘
STANDARDS
POSIX.1-2008.
HISTORY
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.
SEE ALSO
memcmp(3), strcmp(3), strcoll(3), string(3), strncmp(3), wcscasecmp(3),
wcsncasecmp(3)
Linux man-pages 6.9.1 2024-05-02 strcasecmp(3)
Generated by dwww version 1.16 on Tue Dec 16 04:45:49 CET 2025.