Info Catalog octave: Temporary Files octave: C-Style I/O Functions octave: File Positioning

octave: EOF and Errors

 
 14.2.18 End of File and Errors
 ------------------------------
 
 Once a file has been opened its status can be acquired.  As an example
 the ‘feof’ functions determines if the end of the file has been reached.
 This can be very useful when reading small parts of a file at a time.
 The following example shows how to read one line at a time from a file
 until the end has been reached.
 
      filename = "myfile.txt";
      fid = fopen (filename, "r");
      while (! feof (fid) )
        text_line = fgetl (fid);
      endwhile
      fclose (fid);
 
 Note that in some situations it is more efficient to read the entire
 contents of a file and then process it, than it is to read it line by
 line.  This has the potential advantage of removing the loop in the
 above code.
 
  -- : STATUS = feof (FID)
      Return 1 if an end-of-file condition has been encountered for the
      file specified by file descriptor FID and 0 otherwise.
 
      Note that ‘feof’ will only return 1 if the end of the file has
      already been encountered, not if the next read operation will
      result in an end-of-file condition.
 
DONTPRINTYET       See also: fread XREFfread, frewind XREFfrewind, *noteDONTPRINTYET       See also: fread XREFfread, frewind XREFfrewind, 
      fseek XREFfseek, fclear XREFfclear, fopen XREFfopen.
 
  -- : MSG = ferror (FID)
  -- : [MSG, ERR] = ferror (FID)
  -- : [...] = ferror (FID, "clear")
      Query the error status of the stream specified by file descriptor
      FID
 
      If an error condition exists then return a string MSG describing
      the error.  Otherwise, return an empty string "".
 
      The second input "clear" is optional.  If supplied, the error state
      on the stream will be cleared.
 
      The optional second output is a numeric indication of the error
      status.  ERR is 1 if an error condition has been encountered and 0
      otherwise.
 
      Note that ‘ferror’ indicates if an error has already occurred, not
      whether the next operation will result in an error condition.
 
      See also: fclear XREFfclear, fopen XREFfopen.
 
  -- : fclear (FID)
      Clear the stream state for the file specified by the file
      descriptor FID.
 
      See also: ferror XREFferror, fopen XREFfopen.
 
  -- : freport ()
      Print a list of which files have been opened, and whether they are
      open for reading, writing, or both.
 
      For example:
 
           freport ()
 
                ⊣  number  mode  arch       name
                ⊣  ------  ----  ----       ----
                ⊣     0     r    ieee-le    stdin
                ⊣     1     w    ieee-le    stdout
                ⊣     2     w    ieee-le    stderr
                ⊣     3     r    ieee-le    myfile
 
DONTPRINTYET       See also: fopen XREFfopen, fclose XREFfclose, *noteDONTPRINTYET       See also: fopen XREFfopen, fclose XREFfclose, 
      is_valid_file_id XREFis_valid_file_id.
 

Info Catalog octave: Temporary Files octave: C-Style I/O Functions octave: File Positioning