NAME

lseek − move read/write file pointer; seek

SYNOPSIS

#include <unistd.h>
long lseek (fildes, offset, whence)
int fildes;
long offset;
int whence;

DESCRIPTION

Fildes is a file descriptor returned from a creat, open, dup, or fcntl system call.  Lseek sets the file pointer associated with fildes as follows:

If whence is 0, the pointer is set to offset bytes. 

If whence is 1, the pointer is set to its current location plus offset.

If whence is 2, the pointer is set to the size of the file plus offset.

Upon successful completion, the resulting pointer location, as measured in bytes from the beginning of the file, is returned. 

RETURN VALUE

Upon successful completion, a non-negative integer indicating the file pointer value is returned.  Otherwise, a value of −1 is returned and errno is set to indicate the error. 

ERRORS

Lseek will fail and the file pointer will remain unchanged if one or more of the following are true:

­[EBADF] Fildes is not an open file descriptor. 

­[ESPIPE] Fildes is associated with a pipe or fifo. 

­[EINVAL and SIGSYS signal]
Whence is not 0, 1 or 2. 

­[EINVAL] The resulting file pointer would be negative. 

WARNINGS

Some devices are incapable of seeking.  The value of the file pointer associated with such a device is undefined. 

Using lseek with a whence of 2 on device special files is not supported and the results are not defined. 

SEE ALSO

creat(2), dup(2), fcntl(2), open(2). 

Hewlett-Packard Company  —  Version B.1,  May 11, 2021