87 lines
1.9 KiB
Groff
87 lines
1.9 KiB
Groff
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.\" Copyright (c) 1980 Regents of the University of California.
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.\" All rights reserved. The Berkeley software License Agreement
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.\" specifies the terms and conditions for redistribution.
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.\"
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.\" @(#)lseek.2 6.3 (Berkeley) 2/24/86
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.\"
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.TH LSEEK 2 "February 24, 1986"
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.UC 4
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.SH NAME
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lseek \- move read/write pointer
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.SH SYNOPSIS
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.nf
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.ft B
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#include <sys/types.h>
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#include <unistd.h>
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.ta +1.8i +0.6i
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#define SEEK_SET 0 /* offset is absolute */
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#define SEEK_CUR 1 /* relative to current position */
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#define SEEK_END 2 /* relative to end of file */
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off_t lseek(int d, off_t offset, int whence)
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.fi
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.ft R
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.SH DESCRIPTION
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The descriptor
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.I d
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refers to a file or device open for reading and/or writing.
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.B Lseek
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sets the file pointer of
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.I d
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as follows:
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.IP
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If
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.I whence
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is SEEK_SET, the pointer is set to
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.I offset
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bytes.
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.IP
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If
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.I whence
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is SEEK_CUR, the pointer is set to its current location plus
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.IR offset .
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.IP
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If
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.I whence
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is SEEK_END, the pointer is set to the size of the
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file plus
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.IR offset .
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.PP
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Upon successful completion, the resulting pointer location
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as measured in bytes from beginning of the file is returned.
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Some devices are incapable of seeking. The value of the pointer
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associated with such a device is undefined.
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.SH NOTES
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Seeking far beyond the end of a file, then writing,
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creates a gap or \*(lqhole\*(rq, which occupies no
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physical space and reads as zeros.
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.SH "RETURN VALUE
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Upon successful completion,
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the current file pointer value is returned.
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Otherwise,
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a value of \-1 is returned and \fBerrno\fP is set to indicate
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the error.
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.SH "ERRORS
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.B Lseek
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will fail and the file pointer will remain unchanged if:
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.TP 15
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[EBADF]
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.I Fildes
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is not an open file descriptor.
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.TP 15
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[ESPIPE]
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.I Fildes
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is associated with a pipe or a socket.
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.TP 15
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[EINVAL]
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.I Whence
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is not a proper value.
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.SH "SEE ALSO"
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.BR fcntl (2),
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.BR open (2).
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.SH BUGS
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This document's use of
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.I whence
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is incorrect English, but maintained for historical reasons.
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