apue_printf.h

#include <stdio.h>

int printf(const char *restrict format, ...);
int fprintf(FILE *restrict fp, const char *restrict format, ...);
int dprintf(int fd, const char *restrict format, ...);

/* All three return: number of characters output if OK, negative value if output error */

int sprintf(char *restrict buf, const char *restrict format, ...);
/* Returns: number of characters stored in array if OK, negative value if encoding error */

int snprintf(char *restrict buf, size_t n, const char *restrict format, ...);
/* Returns: number of characters that would have been stored in array if buffer was 
   large enough, negative value if encoding error */