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154 lines
4.1 KiB
Groff
154 lines
4.1 KiB
Groff
.\" Copyright (c) 1983, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)truncate.2 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd December 13, 2006
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.Dt TRUNCATE 2
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.Os
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.Sh NAME
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.Nm truncate ,
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.Nm ftruncate
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.Nd truncate or extend a file to a specified length
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In unistd.h
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.Ft int
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.Fn truncate "const char *path" "off_t length"
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.Ft int
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.Fn ftruncate "int fd" "off_t length"
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.Sh DESCRIPTION
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The
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.Fn truncate
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system call
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causes the file named by
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.Fa path
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or referenced by
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.Fa fd
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to be truncated or extended to
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.Fa length
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bytes in size.
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If the file
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was larger than this size, the extra data
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is lost.
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If the file was smaller than this size,
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it will be extended as if by writing bytes
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with the value zero.
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With
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.Fn ftruncate ,
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the file must be open for writing.
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.Sh RETURN VALUES
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.Rv -std
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If the file to be modified is not a directory or
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a regular file, the
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.Fn truncate
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call has no effect and returns the value 0.
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.Sh ERRORS
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The
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.Fn truncate
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system call
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succeeds unless:
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.Bl -tag -width Er
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.It Bq Er ENOTDIR
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A component of the path prefix is not a directory.
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.It Bq Er ENAMETOOLONG
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A component of a pathname exceeded 255 characters,
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or an entire path name exceeded 1023 characters.
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.It Bq Er ENOENT
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The named file does not exist.
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.It Bq Er EACCES
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Search permission is denied for a component of the path prefix.
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.It Bq Er EACCES
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The named file is not writable by the user.
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.It Bq Er ELOOP
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Too many symbolic links were encountered in translating the pathname.
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.It Bq Er EPERM
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The named file has its immutable or append-only flag set, see the
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.Xr chflags 2
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manual page for more information.
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.It Bq Er EISDIR
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The named file is a directory.
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.It Bq Er EROFS
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The named file resides on a read-only file system.
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.It Bq Er ETXTBSY
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The file is a pure procedure (shared text) file that is being executed.
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.It Bq Er EFBIG
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The
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.Fa length
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argument was greater than the maximum file size.
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.It Bq Er EINVAL
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The
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.Fa length
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argument was less than 0.
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.It Bq Er EIO
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An I/O error occurred updating the inode.
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.It Bq Er EFAULT
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The
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.Fa path
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argument
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points outside the process's allocated address space.
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.El
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.Pp
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The
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.Fn ftruncate
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system call
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succeeds unless:
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.Bl -tag -width Er
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.It Bq Er EBADF
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The
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.Fa fd
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argument
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is not a valid descriptor.
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.It Bq Er EINVAL
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The
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.Fa fd
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argument
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references a socket, not a file.
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.It Bq Er EINVAL
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The
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.Fa fd
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descriptor
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is not open for writing.
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.El
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.Sh SEE ALSO
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.Xr chflags 2 ,
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.Xr open 2
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.Sh HISTORY
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The
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.Fn truncate
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system call appeared in
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.Bx 4.2 .
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.Sh BUGS
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These calls should be generalized to allow ranges
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of bytes in a file to be discarded.
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.Pp
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Use of
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.Fn truncate
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to extend a file is not portable.
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