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Test Your Knowledge in Computers #925
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The earliest versions of Unix time had a 32-bit integer incrementing at a rate of 60 Hz.
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lseek(2) [bsd man page]

LSEEK(2)							System Calls Manual							  LSEEK(2)

NAME
lseek - move read/write pointer SYNOPSIS
#include <sys/file.h> #define L_SET 0 /* set the seek pointer */ #define L_INCR 1 /* increment the seek pointer */ #define L_XTND 2 /* extend the file size */ pos = lseek(d, offset, whence) off_t pos; int d; off_t offset; int whence; DESCRIPTION
The descriptor d refers to a file or device open for reading and/or writing. Lseek sets the file pointer of d as follows: If whence is L_SET, the pointer is set to offset bytes. If whence is L_INCR, the pointer is set to its current location plus offset. If whence is L_XTND, the pointer is set to the size of the file plus offset. Upon successful completion, the resulting pointer location as measured in bytes from beginning of the file is returned. Some devices are incapable of seeking. The value of the pointer associated with such a device is undefined. NOTES
Seeking far beyond the end of a file, then writing, creates a gap or "hole", which occupies no physical space and reads as zeros. RETURN VALUE
Upon successful completion, the current 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: [EBADF] Fildes is not an open file descriptor. [ESPIPE] Fildes is associated with a pipe or a socket. [EINVAL] Whence is not a proper value. SEE ALSO
dup(2), open(2) BUGS
This document's use of whence is incorrect English, but maintained for historical reasons. 4th Berkeley Distribution February 24, 1986 LSEEK(2)

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LSEEK(2)							System Calls Manual							  LSEEK(2)

NAME
lseek, tell - move read/write pointer SYNOPSIS
long lseek(fildes, offset, whence) long offset; long tell(fildes) DESCRIPTION
The file descriptor refers to a file open for reading or writing. The read (resp. write) pointer for the file is set 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. The returned value is the resulting pointer location. The obsolete function tell(fildes) is identical to lseek(fildes, 0L, 1). Seeking far beyond the end of a file, then writing, creates a gap or `hole', which occupies no physical space and reads as zeros. SEE ALSO
open(2), creat(2), fseek(3) DIAGNOSTICS
-1 is returned for an undefined file descriptor, seek on a pipe, or seek to a position before the beginning of file. BUGS
Lseek is a no-op on character special files. ASSEMBLER
(lseek = 19.) (file descriptor in r0) sys lseek; offset1; offset2; whence Offset1 and offset2 are the high and low words of offset; r0 and r1 contain the pointer upon return. LSEEK(2)

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