This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       None.

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for  Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical  and  Electronics
       Engineers, Inc and The Open Group.  In the event of any discrepancy between this version and the original
       IEEE  and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document.
       The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are most likely to have  been  introduced
       during   the   conversion  of  the  source  files  to  man  page  format.  To  report  such  errors,  see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                    STRCASECMP(3POSIX)

       The  strcasecmp()  and  strcasecmp_l()  functions  shall compare, while ignoring differences in case, the
       string pointed to by s1 to the string pointed to by s2.  The strncasecmp() and strncasecmp_l()  functions
       shall compare, while ignoring differences in case, not more than n bytes from the string pointed to by s1
       to the string pointed to by s2.

       The  strcasecmp()  and  strncasecmp()  functions  use  the  current  locale  to determine the case of the
       characters.

       The strcasecmp_l() and strncasecmp_l() functions use the locale represented by locale  to  determine  the
       case of the characters.

       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.

       The behavior is undefined if the locale argument to strcasecmp_l()  or  strncasecmp_l()  is  the  special
       locale object LC_GLOBAL_LOCALE or is not a valid locale object handle.

       No errors are defined.

       Thefollowingsectionsareinformative.

       None.

       None.

       strcasecmp, strcasecmp_l, strncasecmp, strncasecmp_l — case-insensitive string comparisons

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (consult the corresponding Linux manual page for details of Linux behavior), or the  interface
       may not be implemented on Linux.

       None.

       Upon  completion, strcasecmp() and strcasecmp_l() shall return an integer greater than, equal to, or less
       than 0, if the string pointed to by s1 is, ignoring case, greater than, equal to, or less than the string
       pointed to by s2, respectively.

       Upon successful completion, strncasecmp() and strncasecmp_l() shall return an integer greater than, equal
       to, or less than 0, if the possibly null-terminated array pointed to by s1  is,  ignoring  case,  greater
       than, equal to, or less than the possibly null-terminated array pointed to by s2, respectively.

wcscasecmp()

       The Base Definitions volume of POSIX.1‐2017, <strings.h>

       #include <strings.h>

       int strcasecmp(const char *s1, const char *s2);
       int strcasecmp_l(const char *s1, const char *s2,
           locale_t locale);
       int strncasecmp(const char *s1, const char *s2, size_t n);
       int strncasecmp_l(const char *s1, const char *s2,
           size_t n, locale_t locale);