1  /* Test the read() function.
       2     Copyright (C) 2011-2023 Free Software Foundation, Inc.
       3  
       4     This program is free software: you can redistribute it and/or modify
       5     it under the terms of the GNU General Public License as published by
       6     the Free Software Foundation, either version 3 of the License, or
       7     (at your option) any later version.
       8  
       9     This program is distributed in the hope that it will be useful,
      10     but WITHOUT ANY WARRANTY; without even the implied warranty of
      11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      12     GNU General Public License for more details.
      13  
      14     You should have received a copy of the GNU General Public License
      15     along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
      16  
      17  #include <config.h>
      18  
      19  #include <unistd.h>
      20  
      21  #include "signature.h"
      22  SIGNATURE_CHECK (read, ssize_t, (int, void *, size_t));
      23  
      24  #include <errno.h>
      25  #include <fcntl.h>
      26  #include <string.h>
      27  
      28  #include "macros.h"
      29  
      30  int
      31  main (void)
      32  {
      33    const char *filename = "test-read.tmp";
      34    int fd;
      35  
      36    /* Create a file with a simple contents.  */
      37    fd = open (filename, O_CREAT | O_WRONLY, 0600);
      38    ASSERT (fd >= 0);
      39    ASSERT (write (fd, "Hello World", 11) == 11);
      40    ASSERT (close (fd) == 0);
      41  
      42    /* Read from the middle of the file.  */
      43    fd = open (filename, O_RDONLY);
      44    ASSERT (fd >= 0);
      45    ASSERT (lseek (fd, 6, SEEK_SET) == 6);
      46    {
      47      char buf[10];
      48      ssize_t ret = read (fd, buf, 10);
      49      ASSERT (ret == 5);
      50      ASSERT (memcmp (buf, "World", 5) == 0);
      51    }
      52    ASSERT (close (fd) == 0);
      53  
      54    /* Test behaviour for invalid file descriptors.  */
      55    {
      56      char byte;
      57      errno = 0;
      58      ASSERT (read (-1, &byte, 1) == -1);
      59      ASSERT (errno == EBADF);
      60    }
      61    {
      62      char byte;
      63      close (99);
      64      errno = 0;
      65      ASSERT (read (99, &byte, 1) == -1);
      66      ASSERT (errno == EBADF);
      67    }
      68  
      69    /* Clean up.  */
      70    unlink (filename);
      71  
      72    return 0;
      73  }