posix/tst-fork.c

   1 /* Tests for fork.
   2    Copyright (C) 2000-2020 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 2000.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <https://www.gnu.org/licenses/>.  */
  19
  20 #include <errno.h>
  21 #include <error.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <unistd.h>
  25 #include <wait.h>
  26
  27
  28 static const char testdata[] = "This is a test";
  29 static const char testdata2[] = "And here we go again";
  30
  31
  32 int
  33 main (void)
  34 {
  35   const char *tmpdir = getenv ("TMPDIR");
  36   char buf[100];
  37   size_t tmpdirlen;
  38   char *name;
  39   int fd;
  40   pid_t pid;
  41   pid_t ppid;
  42   off_t off;
  43   int status;
  44
  45   if (tmpdir == NULL || *tmpdir == '\0')
  46     tmpdir = "/tmp";
  47   tmpdirlen = strlen (tmpdir);
  48
  49   name = (char *) malloc (tmpdirlen + strlen ("/forkXXXXXX") + 1);
  50   if (name == NULL)
  51     error (EXIT_FAILURE, errno, "cannot allocate file name");
  52
  53   mempcpy (mempcpy (name, tmpdir, tmpdirlen),
  54            "/forkXXXXXX", sizeof ("/forkXXXXXX"));
  55
  56   /* Open our test file.   */
  57   fd = mkstemp (name);
  58   if (fd == -1)
  59      error (EXIT_FAILURE, errno, "cannot open test file `%s'", name);
  60
  61   /* Make sure it gets removed.  */
  62   unlink (name);
  63
  64   /* Write some data.  */
  65   if (write (fd, testdata, strlen (testdata)) != strlen (testdata))
  66     error (EXIT_FAILURE, errno, "cannot write test data");
  67
  68   /* Get the position in the stream.  */
  69   off = lseek (fd, 0, SEEK_CUR);
  70   if (off == (off_t) -1 || off != strlen (testdata))
  71     error (EXIT_FAILURE, errno, "wrong file position");
  72
  73   /* Get the parent PID.  */
  74   ppid = getpid ();
  75
  76   /* Now fork of the process.  */
  77   pid = fork ();
  78   if (pid == 0)
  79     {
  80       /* One little test first: the PID must have changed.  */
  81       if (getpid () == ppid)
  82         error (EXIT_FAILURE, 0, "child and parent have same PID");
  83
  84       /* Test the `getppid' function.  */
  85       pid = getppid ();
  86       if (pid == (pid_t) -1 ? errno != ENOSYS : pid != ppid)
  87         error (EXIT_FAILURE, 0,
  88                "getppid returned wrong PID (%ld, should be %ld)",
  89                (long int) pid, (long int) ppid);
  90
  91       /* This is the child.  First get the position of the descriptor.  */
  92       off = lseek (fd, 0, SEEK_CUR);
  93       if (off == (off_t) -1 || off != strlen (testdata))
  94         error (EXIT_FAILURE, errno, "wrong file position in child");
  95
  96       /* Reset the position.  */
  97       if (lseek (fd, 0, SEEK_SET) != 0)
  98         error (EXIT_FAILURE, errno, "cannot reset position in child");
  99
 100       /* Read the data.  */
 101       if (read (fd, buf, sizeof buf) != strlen (testdata))
 102         error (EXIT_FAILURE, errno, "cannot read data in child");
 103
 104       /* Compare the data.  */
 105       if (memcmp (buf, testdata, strlen (testdata)) != 0)
 106         error (EXIT_FAILURE, 0, "data comparison failed in child");
 107
 108       /* Reset position again.  */
 109       if (lseek (fd, 0, SEEK_SET) != 0)
 110         error (EXIT_FAILURE, errno, "cannot reset position again in child");
 111
 112       /* Write new data.  */
 113       if (write (fd, testdata2, strlen (testdata2)) != strlen (testdata2))
 114         error (EXIT_FAILURE, errno, "cannot write new data in child");
 115
 116       /* Close the file.  This must not remove it.  */
 117       close (fd);
 118
 119       _exit (0);
 120     }
 121   else if (pid < 0)
 122     /* Something went wrong.  */
 123     error (EXIT_FAILURE, errno, "cannot fork");
 124
 125   /* Wait for the child.  */
 126   if (waitpid (pid, &status, 0) != pid)
 127     error (EXIT_FAILURE, 0, "Oops, wrong test program terminated");
 128
 129   if (WTERMSIG (status) != 0)
 130     error (EXIT_FAILURE, 0, "Child terminated incorrectly");
 131   status = WEXITSTATUS (status);
 132
 133   if (status == 0)
 134     {
 135       /* Test whether the child wrote the right data.  First test the
 136          position.  It must be the same as in the child.  */
 137       if (lseek (fd, 0, SEEK_CUR) != strlen (testdata2))
 138         error (EXIT_FAILURE, 0, "file position not changed");
 139
 140       if (lseek (fd, 0, SEEK_SET) != 0)
 141         error (EXIT_FAILURE, errno, "cannot reset file position");
 142
 143       if (read (fd, buf, sizeof buf) != strlen (testdata2))
 144         error (EXIT_FAILURE, errno, "cannot read new data");
 145
 146       if (memcmp (buf, testdata2, strlen (testdata2)) != 0)
 147         error (EXIT_FAILURE, 0, "new data not read correctly");
 148     }
 149
 150   return status;
 151 }