strncasecmp(3)             Library Functions Manual             strncasecmp(3)

NAME
       strncasecmp - nonstrings case-insensitive compare

LIBRARY
       Standard C library (libc, -lc)

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

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

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

RETURN VALUE
       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
       For an explanation of the terms used in this section, see
       attributes(7).

       +-------------------------------------+---------------+----------------+
       |Interface                            | Attribute     | Value          |
       +-------------------------------------+---------------+----------------+
       |strncasecmp ()                       | Thread safety | MT-Safe locale |
       +-------------------------------------+---------------+----------------+
STANDARDS
       POSIX.1-2008.

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

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