Positions the file to the specified byte offset in the file.
Format
#include <stdio.h>
int fseek (FILE *file_ptr, long int offset, int
direction);
Arguments
- file_ptr
- A file pointer.
- offset
- The offset, specified in bytes.
- direction
- An integer indicating whether the offset is to be measured
forward from the beginning of the file (direction=SEEK_SET), forward
from the current position (direction=SEEK_CUR), or backward from the
end of the file (direction=SEEK_END).
Description
This function can position fixed-length record-access file
with no carriage control or a stream-access file on any byte offset,
but can position all other files only on record boundaries.
The available Standard I/O functions position a variable-length
or VFC record file at its first byte, at the end-of-file, or on
a record boundary. Therefore, the arguments given to fseek must
specify any of the following:
- The beginning or end of the file
- A 0 offset from the current position (an arbitrary record
boundary)
- The position returned by a previous, valid ftell call
See the fgetpos and fsetpos functions for a portable way to seek to
arbitrary locations with these types of record files.
- CAUTION
- If, while accessing a stream
file, you seek beyond the end-of-file and then write to the file,
the fseek function creates a hole by filling the skipped bytes with
zeros.
In general, for record files, fseek should only be directed to an
absolute position that was returned by a previous valid call to
ftell, or to the beginning or end of a file. If a call to fseek does
not satisfy these conditions, the results are unpredictable.
See also open, creat, dup, dup2, and lseek in this section.
Return Values
| 0 | Indicates successful
seeks. |
| -1 | Indicates
improper seeks. |
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