NAME

fseek, rewind, ftell − reposition a file pointer in a stream

SYNOPSIS

#include <stdio.h>

int fseek (stream, offset, ptrname)
FILE ∗stream;
long offset;
int ptrname;

long rewind (stream)
FILE ∗stream;

long ftell (stream)
FILE ∗stream;

HP-UX COMPATIBILITY

Level: HP-UX/RUN ONLY

Origin: System V

DESCRIPTION

Fseek sets the position of the next input or output operation on the stream. The new position is at the signed distance offset bytes from the beginning, from the current position, or from the end of the file, according as ptrname has the value 0, 1, or 2. 

Rewind(stream) is equivalent to fseek(stream, 0L, 0).

Fseek and rewind undo any effects of ungetc(3S).

After fseek or rewind, the next operation on a file opened for update may be either input or output. Rewind also does an implicit clearerr(3s) call.

Ftell returns the offset of the current byte relative to the beginning of the file associated with the named stream.

SEE ALSO

lseek(2), fopen(3S), popen(3S), ungetc(3S). 

DIAGNOSTICS

Fseek returns non-zero for improper seeks, otherwise zero.  An improper seek can be, for example, an fseek done on a file that has not been opened via fopen; in particular, fseek may not be used on a terminal, or on a file opened via popen(3S).

Ftell returns -1 for error conditions. 

WARNING

Although on HP-UX an offset returned by ftell is measured in bytes, and it is permissible to seek to positions relative to that offset, portability to non-UNIX systems requires that an offset be used by fseek directly. Arithmetic may not meaningfully be performed on such an offset, which is not necessarily measured in bytes. 

Hewlett-Packard  —  last mod. May 11, 2021