external/ibm-public/postfix/dist/src/util/dup2_pass_on_exec.c

   1 /*      $NetBSD$        */
   2
   3 /*++
   4 /* NAME
   5 /*      dup2_pass_on_exec 1
   6 /* SUMMARY
   7 /*      dup2 close-on-exec behaviour test program
   8 /* SYNOPSIS
   9 /*      dup2_pass_on_exec
  10 /* DESCRIPTION
  11 /*      dup2_pass_on_exec sets the close-on-exec flag on its
  12 /*      standard input and then dup2() to duplicate it.
  13 /*      Posix-1003.1 specifies in section 6.2.1.2 that dup2(o,n) should behave
  14 /*      as: close(n); n = fcntl(o, F_DUPFD, n); as long as o is a valid
  15 /*      file-descriptor, n!=o, and 0<=n<=[OPEN_MAX].
  16 /*      Section 6.5.2.2 states that the close-on-exec flag of the result of a
  17 /*      successful fcntl(o, F_DUPFD, n) is cleared.
  18 /*
  19 /*      At least Ultrix4.3a does not clear the close-on-exec flag of n on
  20 /*      dup2(o, n).
  21 /* DIAGNOSTICS
  22 /*      Problems are reported to the standard error stream.
  23 /* LICENSE
  24 /* .ad
  25 /* .fi
  26 /*      The Secure Mailer license must be distributed with this software.
  27 /* AUTHOR(S)
  28 /*      Christian von Roques <roques@pond.sub.org>
  29 /*      Forststrasse 71
  30 /*      76131 Karlsruhe, GERMANY
  31 /*--*/
  32
  33 #include <stdio.h>
  34 #include <fcntl.h>
  35 #include <unistd.h>
  36 #include <stdlib.h>
  37
  38 #define DO(s)   if (s < 0) { perror(#s); exit(1); }
  39
  40 int     main(int unused_argc, char **unused_argv)
  41 {
  42     int     res;
  43
  44     printf("Setting the close-on-exec flag of file-descriptor 0.\n");
  45     DO(fcntl(0, F_SETFD, 1));
  46
  47     printf("Duplicating file-descriptor 0 to 3.\n");
  48     DO(dup2(0, 3));
  49
  50     printf("Testing if the close-on-exec flag of file-descriptor 3 is set.\n");
  51     DO((res = fcntl(3, F_GETFD, 0)));
  52     if (res & 1)
  53         printf(
  54 "Yes, a newly dup2()ed file-descriptor has the close-on-exec \
  55 flag cloned.\n\
  56 THIS VIOLATES Posix1003.1 section 6.2.1.2 or 6.5.2.2!\n\
  57 You should #define DUP2_DUPS_CLOSE_ON_EXEC in sys_defs.h \
  58 for your OS.\n");
  59     else
  60         printf(
  61 "No, a newly dup2()ed file-descriptor has the close-on-exec \
  62 flag cleared.\n\
  63 This complies with Posix1003.1 section 6.2.1.2 and 6.5.2.2!\n");
  64
  65     return 0;
  66 }