fgetwc, getwc

#include <stdio.h>
#include <stdlib.h>
#include <wchar.h>
#include <errno.h>
#include <locale.h>
 
int main(void)
{
 setlocale (LC_ALL, "en_US.utf8");
 FILE *fp = fopen ("fgetwc.dat", "w");
 if(!fp) {
 perror ("Can't open file for writing");
 return EXIT_FAILURE ;
 }
 fputs ("кошка\n", fp);
 fclose (fp);
 
 fp = fopen ("fgetwc.dat", "r");
 if(!fp) {
 perror ("Can't open file for reading");
 return EXIT_FAILURE ;
 }
 wint_t wc;
 errno = 0;
 while ((wc = fgetwc(fp)) != WEOF)
 putwchar (wc);
 
 if (ferror (fp)) {
 if (errno == EILSEQ )
 puts ("Character encoding error while reading.");
 else
 puts ("I/O error when reading");
 } else if (feof (fp))
 puts ("End of file reached successfully");
 
 fclose (fp);
}

кошка