/*
 Test 'setlocale()' behaviour.
 Copyright (C) 2016 Assaf Gordon
 license: GNU All permissive license.
 
 compile:
    cc -o print-locale print-locale.c
 test:
    ./print-locale
    LC_ALL=C ./print-locale
    LC_ALL=missing ./print-locale
*/
#include <locale.h>
#include <stdlib.h>
#include <stdio.h>

int main(void)
{
  char* p = getenv("LC_ALL");
  printf("LC_ALL env var = '%s'\n", p?p:"(NULL)");

  p = setlocale(LC_ALL,"");
  printf("setlocale(LC_ALL,\"\") = '%s'\n", p?p:"(NULL)");
  
  p = setlocale(LC_ALL,NULL);
  printf("LC_ALL from setlocale = '%s'\n", p?p:"(NULL)");

  p = setlocale(LC_COLLATE,NULL);
  printf("LC_COLLATE from setlocale = '%s'\n", p?p:"(NULL)");

  return 0;
}

==== glibc (Ubuntu) ====

$ ./print-locale 
LC_ALL env var = '(NULL)'
setlocale(LC_ALL,"") = 'en_US.UTF-8'
LC_ALL from setlocale = 'en_US.UTF-8'
LC_COLLATE from setlocale = 'en_US.UTF-8'

$ LC_ALL=C ./print-locale 
LC_ALL env var = 'C'
setlocale(LC_ALL,"") = 'C'
LC_ALL from setlocale = 'C'
LC_COLLATE from setlocale = 'C'

$ LC_ALL=missing ./print-locale 
LC_ALL env var = 'missing'
setlocale(LC_ALL,"") = '(NULL)'
LC_ALL from setlocale = 'C'
LC_COLLATE from setlocale = 'C'


==== musl libc =======

$ ./print-locale
LC_ALL env var = '(NULL)'
setlocale(LC_ALL,"") = 'C.UTF-8;C;C;C;C;C'
LC_ALL from setlocale = 'C.UTF-8;C;C;C;C;C'
LC_COLLATE from setlocale = 'C'

$ LC_ALL=c ./print-locale
LC_ALL env var = 'C'
setlocale(LC_ALL,"") = 'C;C;C;C;C;C'
LC_ALL from setlocale = 'C;C;C;C;C;C'
LC_COLLATE from setlocale = 'C'

$ LC_ALL=missing ./print-locale
LC_ALL env var = 'missing'
setlocale(LC_ALL,"") = 'missing;missing;missing;missing;missing;missing'
LC_ALL from setlocale = 'missing;missing;missing;missing;missing;missing'
LC_COLLATE from setlocale = 'missing'

==== FreeBSD ==== 

$ ./print-locale
LC_ALL env var = '(NULL)'
setlocale(LC_ALL,"") = 'C'
LC_ALL from setlocale = 'C'
LC_COLLATE from setlocale = 'C'

$ LC_ALL=C ./print-locale
LC_ALL env var = 'C'
setlocale(LC_ALL,"") = 'C'
LC_ALL from setlocale = 'C'
LC_COLLATE from setlocale = 'C'

$ LC_ALL=missing ./print-locale
LC_ALL env var = 'missing'
setlocale(LC_ALL,"") = '(NULL)'
LC_ALL from setlocale = 'C'
LC_COLLATE from setlocale = 'C'


==== OpenBSD ====

$ ./print-locale                                                               
LC_ALL env var = '(NULL)'
setlocale(LC_ALL,"") = 'C'
LC_ALL from setlocale = 'C'
LC_COLLATE from setlocale = 'C'

$ LC_ALL=C ./print-locale                                                      
LC_ALL env var = 'C'
setlocale(LC_ALL,"") = 'C'
LC_ALL from setlocale = 'C'
LC_COLLATE from setlocale = 'C'

$ LC_ALL=missing ./print-locale
LC_ALL env var = 'missing'
setlocale(LC_ALL,"") = 'C/missing/C/C/C/C'
LC_ALL from setlocale = 'C/missing/C/C/C/C'
LC_COLLATE from setlocale = 'C'