GNU Octave Manual Version 3 by John W. Eaton, David Bateman, Søren Hauberg Paperback (6"x9"), 568 pages ISBN 095461206X RRP £24.95 ($39.95) |
14.2.19 File Positioning
Three functions are available for setting and determining the position of the file pointer for a given file.
- Built-in Function: ftell (fid)
- Return the position of the file pointer as the number of characters
from the beginning of the file fid.
See also fseek, fopen, fclose
- Built-in Function: fseek (fid, offset, origin)
- Set the file pointer to any location within the file fid.
The pointer is positioned offset characters from the origin, which may be one of the predefined variables
SEEK_CUR
(current position),SEEK_SET
(beginning), orSEEK_END
(end of file) or strings "cof", "bof" or "eof". If origin is omitted,SEEK_SET
is assumed. The offset must be zero, or a value returned byftell
(in which case origin must beSEEK_SET
).Return 0 on success and -1 on error.
See also ftell, fopen, fclose
- Built-in Function: SEEK_SET ()
- Built-in Function: SEEK_CUR ()
- Built-in Function: SEEK_END ()
- Return the value required to request that
fseek
perform one of the following actions:SEEK_SET
- Position file relative to the beginning.
SEEK_CUR
- Position file relative to the current position.
SEEK_END
- Position file relative to the end.
- Built-in Function: frewind (fid)
- Move the file pointer to the beginning of the file fid, returning
0 for success, and -1 if an error was encountered. It is equivalent to
fseek (fid, 0, SEEK_SET)
.
The following example stores the current file position in the variable
marker
, moves the pointer to the beginning of the file, reads
four characters, and then returns to the original position.
marker = ftell (myfile); frewind (myfile); fourch = fgets (myfile, 4); fseek (myfile, marker, SEEK_SET);
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