1 /* $OpenBSD: fcntl_dup.c,v 1.3 2017/07/27 10:42:24 bluhm Exp $ */ 2 /* 3 * Written by Artur Grabowski <art@openbsd.org> 2002 Public Domain. 4 */ 5 #include <stdio.h> 6 #include <stdlib.h> 7 #include <unistd.h> 8 #include <err.h> 9 #include <fcntl.h> 10 11 int 12 main(int argc, char *argv[]) 13 { 14 int orgfd, fd1, fd2; 15 char temp[] = "/tmp/dup2XXXXXXXXX"; 16 17 if ((orgfd = mkstemp(temp)) < 0) 18 err(1, "mkstemp"); 19 remove(temp); 20 21 if (ftruncate(orgfd, 1024) != 0) 22 err(1, "ftruncate"); 23 24 if ((fd1 = dup(orgfd)) < 0) 25 err(1, "dup"); 26 27 /* Set close-on-exec */ 28 if (fcntl(fd1, F_SETFD, 1) != 0) 29 err(1, "fcntl(F_SETFD)"); 30 31 if ((fd2 = fcntl(fd1, F_DUPFD, 0)) < 0) 32 err(1, "fcntl(F_DUPFD)"); 33 34 /* Test 2: Was close-on-exec cleared? */ 35 if (fcntl(fd2, F_GETFD) != 0) 36 errx(1, "fcntl(F_DUPFD) didn't clear close-on-exec"); 37 38 return 0; 39 } 40