DragonFlyBSD

#include <stdio.h>

int

main(void)

{

        FILE *f = fopen("duptmp", "w");

        FILE *f1, *f2;

        char line[100];

        if (f == NULL)

                return (1);

        fputs("1\n2\n3\n", f);

        fclose(f);

        f1 = fopen("duptmp", "r");

        if (f1 == NULL)

                return (1);

        f2 = fdopen(dup(fileno(f1)), "r");

        if (f2 == NULL)

                return (2);

        fgets(line, sizeof(line), f1);

        printf("read1: %s", line);

        fgets(line, sizeof(line), f2);

        printf("read2: %s", line);

        return (0);

}