lseek(2) [sunos man page]

lseek(2)							   System Calls 							  lseek(2)

NAME

       lseek - move read/write file pointer

SYNOPSIS

       #include <sys/types.h>
       #include <unistd.h>

       off_t lseek(int fildes, off_t offset, int whence);

DESCRIPTION

       The lseek() function sets the file pointer associated with the open file descriptor specified by fildes as follows:

	 o  If whence is SEEK_SET, the pointer is set to offset bytes.

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

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

       The symbolic constants SEEK_SET, SEEK_CUR, and SEEK_END are defined in the header <unistd.h>.

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

       The  lseek() function allows the file pointer to be set beyond the existing data in the file. If data are later written at this point, sub-
       sequent reads in the gap between the previous end of data and the newly written data will return bytes of value 0 until	data  are  written
       into the gap.

       If  fildes  is a remote file descriptor and offset is negative, lseek() returns the file pointer  even if it is negative. The lseek() func-
       tion will not, by itself, extend the size of a file.

       If fildes refers to a shared memory object, lseek() behaves as if fildes referred to a regular file.

RETURN VALUES

       Upon successful completion, the resulting offset, as measured in bytes from the beginning of the file, is returned. Otherwise, (off_t)-1 is
       returned, the file offset remains unchanged, and errno is set to indicate the error.

ERRORS

       The lseek() function will fail if:

       EBADF	       The fildes argument is not an open file descriptor.

       EINVAL	       The  whence argument is not SEEK_SET, SEEK_CUR, or SEEK_END; or the fildes argument is not a remote file descriptor and the
		       resulting file pointer would be negative.

       EOVERFLOW       The resulting file offset would be a value which cannot be represented correctly in an object of  type  off_t  for  regular
		       files.

       ESPIPE	       The fildes argument is associated with a pipe, a FIFO, or a socket.

USAGE

       The lseek() function has a transitional interface for 64-bit file offsets.  See lf64(5).

       In  multithreaded  applications,  using lseek() in conjunction with a read(2) or write(2) call on a file descriptor shared by more than one
       thread is not an atomic operation.  To ensure atomicity, use pread() or pwrite().

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Async-Signal-Safe 	   |
       +-----------------------------+-----------------------------+

SEE ALSO

       creat(2), dup(2), fcntl(2), open(2), read(2), write(2), attributes(5), lf64(5), standards(5)

SunOS 5.10							    17 Apr 2002 							  lseek(2)

Check Out this Related Man Page

lseek(2)							System Calls Manual							  lseek(2)

Name
       lseek, tell - move read or write pointer

Syntax
       #include <sys/types.h>
       #include <unistd.h>

       pos = lseek(d, offset, whence)
       off_t pos;
       int d, whence;
       off_t offset;

       pos = tell(d)
       off_t pos;
       int d;

Description
       The system call moves the file pointer associated with a file or device open for reading or writing.

       The descriptor d refers to a file or device open for reading or writing.  The system call sets the file pointer of d as follows:

       o    If whence is SEEK_SET, the pointer is set to offset bytes.

       o    If whence is SEEK_CUR the pointer is set to its current location plus offset.

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

       Seeking beyond the end of a file and then writing to the file creates a gap or hole that does not occupy physical space and reads as zeros.

       The system call returns the offset of the current byte relative to the beginning of the file associated with the file descriptor.

Environment
   System Five
       If  you	compile  a  program  in  the System Five environment, an invalid whence argument causes SIGSYS to be sent.  This complies with the
       behavior described in the System V Interface Definition (SVID), Issue 1.

Return Values
       Upon successful completion, a long integer (the current file pointer value) is returned.  This pointer is measured in bytes from the begin-
       ning  of  the file, where the first byte is byte 0.  (Note that some devices are incapable of seeking.  The value of the pointer associated
       with such a device is undefined.)  If a value of -1 is returned, errno is set to indicate the error.

Diagnostics
       The system call fails and the file pointer remains unchanged under the following conditions:

       [EBADF]	      The fildes is not an open file descriptor.

       [EINVAL]       The whence is not a proper value.

       [ESPIPE]       The fildes is associated with a pipe or a socket.

See Also
       dup(2), open(2)

																	  lseek(2)

Linux and UNIX Man Pages

lseek(2) [sunos man page]

Check Out this Related Man Page