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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | STANDARDS | HISTORY | SEE ALSO | COLOPHON |
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strcasecmp(3) Library Functions Manual strcasecmp(3)
strcasecmp - strings case-insensitive compare
Standard C library (libc, -lc)
#include <strings.h>
int strcasecmp(const char *s1, const char *s2);
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 strcasecmp() function returns 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() │ Thread safety │ MT-Safe locale │
└───────────────────────────────┴───────────────┴────────────────┘
POSIX.1-2008.
4.4BSD, POSIX.1-2001.
strcasecmp() first appeared in 4.4BSD, where it was declared in
<string.h>. Thus, for reasons of historical compatibility, the
glibc <string.h> header file also declares this function, 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 this function:
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.
strcmp(3), string(3), wcscasecmp(3)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
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2026-09-09. If you discover any rendering problems in this HTML
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Linux man-pages 6.19 2026-08-10 strcasecmp(3)
Pages that refer to this page: strcmp(3), string(3), strncasecmp(3), wcscasecmp(3)
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HTML rendering created 2026-09-09 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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