206 lines
6.4 KiB
Groff
206 lines
6.4 KiB
Groff
.\" $NetBSD: pathconf.2,v 1.2 1995/02/27 12:35:22 cgd Exp $
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.\"
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.\" Copyright (c) 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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.\" @(#)pathconf.2 8.1 (Berkeley) 6/4/93
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.\"
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.Dd June 4, 1993
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.Dt PATHCONF 2
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.Os BSD 4
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.Sh NAME
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.Nm fpathconf ,
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.Nm pathconf
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.Nd get configurable pathname variables
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.Sh SYNOPSIS
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.Fd #include <unistd.h>
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.Ft long
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.Fo fpathconf
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.Fa "int fildes"
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.Fa "int name"
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.Fc
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.Ft long
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.Fo pathconf
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.Fa "const char *path"
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.Fa "int name"
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.Fc
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.Sh DESCRIPTION
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.Pp
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The
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.Fn pathconf
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and
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.Fn fpathconf
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functions provides a method for applications to determine the current
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value of a configurable system limit or option variable associated
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with a pathname or file descriptor.
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.Pp
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For
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.Nm pathconf ,
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the
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.Fa path
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argument is the name of a file or directory.
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For
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.Nm fpathconf ,
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the
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.Fa fildes
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argument is an open file descriptor.
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The
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.Fa name
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argument specifies the system variable to be queried.
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Symbolic constants for each name value are found in the include file
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.Li <unistd.h> .
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.Pp
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The available values are as follows:
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.Pp
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.Bl -tag -width "123456"
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.Pp
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.It Li _PC_LINK_MAX
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The maximum file link count.
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.It Li _PC_MAX_CANON
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The maximum number of bytes in terminal canonical input line.
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.It Li _PC_MAX_INPUT
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The minimum maximum number of bytes for which space is available in
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a terminal input queue.
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.It Li _PC_NAME_MAX
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The maximum number of bytes in a file name.
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.It Li _PC_PATH_MAX
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The maximum number of bytes in a pathname.
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.It Li _PC_PIPE_BUF
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The maximum number of bytes which will be written atomically to a pipe.
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.It Li _PC_CHOWN_RESTRICTED
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Return 1 if appropriate privileges are required for the
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.Xr chown 2
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system call, otherwise 0.
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.It Li _PC_NO_TRUNC
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Return 1 if file names longer than KERN_NAME_MAX are truncated.
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.It Li _PC_VDISABLE
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Returns the terminal character disabling value.
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.It Li _PC_FILESIZEBITS
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The minimum number of bits needed to represent, as a signed integer value, the maximum size of a regular file allowed in the specified directory. The max file size is 2^(_PC_FILESIZEBITS - 1).
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.It Li _PC_XATTR_SIZE_BITS
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Returns the number of bits used to store maximum extended
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attribute size in bytes. For example, if the maximum
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attribute size supported by a file system is 128K, the
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value returned will be 18. However a value 18 can mean
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that the maximum attribute size can be anywhere from
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(256KB - 1) to 128KB. As a special case, the resource
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fork can have much larger size, and some file system
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specific extended attributes can have smaller and preset
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size; for example, Finder Info is always 32 bytes.
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.It Li _PC_MIN_HOLE_SIZE
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If a file system supports the reporting of holes (see
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.Xr lseek 2 ) ,
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.Fn pathconf
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and
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.Fn fpathconf
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return a positive number that represents the minimum hole size returned in
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bytes.
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The offsets of holes returned will be aligned to this same value.
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A special value of 1 is returned if the file system does not specify the minimum
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hole size but still reports holes.
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.El
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.Sh RETURN VALUES
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If the call to
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.Nm pathconf
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or
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.Nm fpathconf
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is not successful, \-1 is returned and
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.Va errno
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is set appropriately.
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Otherwise, if the variable is associated with functionality that does
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not have a limit in the system, \-1 is returned and
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.Va errno
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is not modified.
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Otherwise, the current variable value is returned.
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.Sh ERRORS
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If any of the following conditions occur, the
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.Nm pathconf
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and
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.Nm fpathconf
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functions shall return -1 and set
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.Va errno
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to the corresponding value.
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.Bl -tag -width ENAMETOOLONGAA
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.\" ===========
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.It Bq Er EINVAL
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The value of the
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.Fa name
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argument is invalid.
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.\" ===========
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.It Bq Er EINVAL
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The implementation does not support an association of the variable
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name with the associated file.
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.El
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.Pp
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.Fn pathconf
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will fail if:
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.Bl -tag -width ENAMETOOLONGAA
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.\" ===========
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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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.\" ===========
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.It Bq Er EIO
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An I/O error occurs while reading from or writing to the file system.
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.\" ===========
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.It Bq Er ELOOP
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Too many symbolic links are encountered in translating the pathname.
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This is taken to be indicative of a looping symbolic link.
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.\" ===========
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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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.\" ===========
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.It Bq Er ENOENT
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The named file does not exist.
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.\" ===========
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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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.El
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.Pp
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.Bl -tag -width ENAMETOOLONGAA
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.Fn fpathconf
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will fail if:
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.\" ===========
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.It Bq Er EBADF
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.Fa fildes
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is not a valid open file descriptor.
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.\" ===========
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.It Bq Er EIO
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An I/O error occurs while reading from or writing to the file system.
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.El
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.Sh SEE ALSO
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.Xr sysctl 3
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.Sh HISTORY
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The
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.Nm pathconf
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and
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.Nm fpathconf
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functions first appeared in 4.4BSD.
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