strncasecmp(3) — Linux manual page

strncasecmp(3)           Library Functions Manual          strncasecmp(3)

NAME         top

       strncasecmp - nonstrings case-insensitive compare

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <strings.h>  // see memory.h(3head)

       int strncasecmp(const char s1[], const char s2[], size_t n);

DESCRIPTION         top

       The strncasecmp() function is similar to strcasecmp(3), except
       that it compares no more than n bytes of s1 and s2.

RETURN VALUE         top

       The strncasecmp() 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.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       attributes(7).
       ┌───────────────────────────────┬───────────────┬────────────────┐
       │ Interface                     │ Attribute     │ Value          │
       ├───────────────────────────────┼───────────────┼────────────────┤
       │ strncasecmp()                 │ Thread safety │ MT-Safe locale │
       └───────────────────────────────┴───────────────┴────────────────┘

STANDARDS         top

       POSIX.1-2008.

HISTORY         top

       4.4BSD, POSIX.1-2001.

       strncasecmp() 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 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         top

       memory.h(3head), strncmp(3), wcsncasecmp(3)

COLOPHON         top

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Linux man-pages 6.19            2026-08-10                 strncasecmp(3)

Pages that refer to this page: memory.h(3head),  strncmp(3),  wcscasecmp(3)

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