Skip to content
  • Ulrich Drepper's avatar
    flag parameters: dup2 · 336dd1f7
    Ulrich Drepper authored
    
    
    This patch adds the new dup3 syscall.  It extends the old dup2 syscall by one
    parameter which is meant to hold a flag value.  Support for the O_CLOEXEC flag
    is added in this patch.
    
    The following test must be adjusted for architectures other than x86 and
    x86-64 and in case the syscall numbers changed.
    
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    #include <fcntl.h>
    #include <stdio.h>
    #include <time.h>
    #include <unistd.h>
    #include <sys/syscall.h>
    
    #ifndef __NR_dup3
    # ifdef __x86_64__
    #  define __NR_dup3 292
    # elif defined __i386__
    #  define __NR_dup3 330
    # else
    #  error "need __NR_dup3"
    # endif
    #endif
    
    int
    main (void)
    {
      int fd = syscall (__NR_dup3, 1, 4, 0);
      if (fd == -1)
        {
          puts ("dup3(0) failed");
          return 1;
        }
      int coe = fcntl (fd, F_GETFD);
      if (coe == -1)
        {
          puts ("fcntl failed");
          return 1;
        }
      if (coe & FD_CLOEXEC)
        {
          puts ("dup3(0) set close-on-exec flag");
          return 1;
        }
      close (fd);
    
      fd = syscall (__NR_dup3, 1, 4, O_CLOEXEC);
      if (fd == -1)
        {
          puts ("dup3(O_CLOEXEC) failed");
          return 1;
        }
      coe = fcntl (fd, F_GETFD);
      if (coe == -1)
        {
          puts ("fcntl failed");
          return 1;
        }
      if ((coe & FD_CLOEXEC) == 0)
        {
          puts ("dup3(O_CLOEXEC) set close-on-exec flag");
          return 1;
        }
      close (fd);
    
      puts ("OK");
    
      return 0;
    }
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    
    Signed-off-by: default avatarUlrich Drepper <drepper@redhat.com>
    Acked-by: default avatarDavide Libenzi <davidel@xmailserver.org>
    Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
    Cc: <linux-arch@vger.kernel.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    336dd1f7