07506ce5eb
normally lengtens the file if it's shorter than specified length also change wording slighly, to match wording in SUS XXX someone should check how much of SUS truncate(2) specification is true XXX on NetBSD and update this manpage accordingly
137 lines
4.1 KiB
Groff
137 lines
4.1 KiB
Groff
.\" $NetBSD: truncate.2,v 1.11 2000/05/28 09:41:52 jdolecek Exp $
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.\"
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.\" 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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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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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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.\"
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.Dd June 4, 1993
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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 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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.Fd #include <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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.Fn truncate
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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 have a size of
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.Fa length
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bytes. If the file previously
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was larger than this size, the extra data
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is discarded. If it was previously shorter than
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.Fa length ,
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its size is increased to the specified value and
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the extended area appears as if it were zero-filled.
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With
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.Fn ftruncate ,
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the file must be open for writing; for
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.Fn truncate ,
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the process must have write permissions for the file.
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.Sh RETURN VALUES
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A value of 0 is returned if the call succeeds. If the call
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fails a -1 is returned, and the global variable
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.Va errno
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specifies the error.
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.Sh ERRORS
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.Fn truncate
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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
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.Dv {NAME_MAX}
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characters, or an entire path name exceeded
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.Dv {PATH_MAX}
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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 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 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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.Fa path
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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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.Fn ftruncate
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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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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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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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is not open for writing.
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.El
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.Sh SEE ALSO
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.Xr open 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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.Sh HISTORY
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The
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.Fn truncate
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and
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.Fn ftruncate
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function calls appeared in
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.Bx 4.2 .
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