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Top Forums Programming Cannot read a file with read(fd, buffer, buffersize) function Post 302324786 by achenle on Thursday 11th of June 2009 10:02:41 PM
Old 06-11-2009
You can't read from or write to a file descriptor after you close it. You need to remove the close() statements:

Code:
           .
           .
           .
          close (fRead);  <--- 
          if (fPadded =creat (argv[2], S_IRWXU) ==-1 )
          {
                    printf ("An error has occurred writing the file.\n");
                    return 0;
          }
          else
          {
             close (fPadded);   <---
               .
               .
               .

 

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close(2)							System Calls Manual							  close(2)

NAME
close - close a file descriptor SYNOPSIS
DESCRIPTION
closes the file descriptor indicated by fildes. fildes is a file descriptor obtained from a or system call. All associated file segments which have been locked by this process with the function are released (i.e., unlocked). RETURN VALUE
Upon successful completion, returns a value of 0; otherwise, it returns -1 and sets to indicate the error. ERRORS
fails if the any of following conditions are encountered: [EBADF] fildes is not a valid open file descriptor. [EINTR] An attempt to close a slow device or connection or file with pending aio requests was interrupted by a signal. The file descriptor still points to an open device or connection or file. [ENOSPC] Not enough space on the file system. This error can occur when closing a file on an NFS file system. [When a system call is executed on a local file system and if a new buffer needs to be allocated to hold the data, the buffer is mapped onto the disk at that time. A full disk is detected at this time and returns an error. When the system call is executed on an NFS file system, the new buffer is allocated without communicating with the NFS server to see if there is space for the buffer (to improve NFS performance). It is only when the buffer is written to the server (at file close or the buffer is full) that the disk-full condition is detected.] SEE ALSO
creat(2), dup(2), exec(2), fcntl(2), lockf(2), open(2), pipe(2), thread_safety(5). STANDARDS CONFORMANCE
close(2)
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