09784497a2
if the new file mode is the same as it was before; however, this optimization must be disabled for filesystems that support NFSv4 ACLs. Chmod uses pathconf(2) to determine whether this is the case - however, pathconf(2) always follows symbolic links, while the 'chmod -h' doesn't. This change adds lpathconf(3) to make it possible to solve that problem in a clean way. Reviewed by: rwatson (earlier version) Approved by: re (kib)
264 lines
7.5 KiB
Groff
264 lines
7.5 KiB
Groff
.\" 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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.\" 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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.\" $FreeBSD$
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.\"
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.Dd July 7, 2009
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.Dt PATHCONF 2
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.Os
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.Sh NAME
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.Nm pathconf ,
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.Nm lpathconf ,
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.Nm fpathconf
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.Nd get configurable pathname variables
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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 long
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.Fn pathconf "const char *path" "int name"
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.Ft long
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.Fn lpathconf "const char *path" "int name"
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.Ft long
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.Fn fpathconf "int fd" "int name"
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.Sh DESCRIPTION
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The
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.Fn pathconf ,
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.Fn lpathconf
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and
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.Fn fpathconf
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system calls provide 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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.Fn pathconf
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and
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.Fn lpathconf ,
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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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.Fn fpathconf ,
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the
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.Fa fd
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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
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.Fn lpathconf
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system call is like
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.Fn pathconf
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except in the case where the named file is a symbolic link,
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in which case
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.Fn lpathconf
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returns information about the link,
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while
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.Fn pathconf
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returns information about the file the link references.
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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 6n
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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 privilege is required for the
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.Xr chown 2
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system call, otherwise 0.
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.St -p1003.1-2001
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requires appropriate privilege in all cases, but this behavior was optional
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in prior editions of the standard.
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.It Li _PC_NO_TRUNC
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Return greater than zero if attempts to use pathname components longer than
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.Brq Dv NAME_MAX
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will result in an
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.Bq Er ENAMETOOLONG
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error; otherwise, such components will be truncated to
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.Brq Dv NAME_MAX .
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.St -p1003.1-2001
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requires the error in all cases, but this behavior was optional in prior
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editions of the standard, and some
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.No non- Ns Tn POSIX Ns -compliant
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file systems do not support this behavior.
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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_ASYNC_IO
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Return 1 if asynchronous I/O is supported, otherwise 0.
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.It Li _PC_PRIO_IO
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Returns 1 if prioritised I/O is supported for this file,
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otherwise 0.
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.It Li _PC_SYNC_IO
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Returns 1 if synchronised I/O is supported for this file, otherwise 0.
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.It Li _PC_ALLOC_SIZE_MIN
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Minimum number of bytes of storage allocated for any portion of a file.
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.It Li _PC_FILESIZEBITS
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Number of bits needed to represent the maximum file size.
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.It Li _PC_REC_INCR_XFER_SIZE
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Recommended increment for file transfer sizes between
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.Dv _PC_REC_MIN_XFER_SIZE
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and
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.Dv _PC_REC_MAX_XFER_SIZE .
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.It Li _PC_REC_MAX_XFER_SIZE
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Maximum recommended file transfer size.
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.It Li _PC_REC_MIN_XFER_SIZE
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Minimum recommended file transfer size.
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.It Li _PC_REC_XFER_ALIGN
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Recommended file transfer buffer alignment.
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.It Li _PC_SYMLINK_MAX
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Maximum number of bytes in a symbolic link.
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.It Li _PC_ACL_EXTENDED
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Returns 1 if an Access Control List (ACL) can be set on the specified
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file, otherwise 0.
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.It Li _PC_ACL_NFS4
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Returns 1 if an NFSv4 ACLs can be set on the specified
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file, otherwise 0.
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.It Li _PC_ACL_PATH_MAX
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Maximum number of ACL entries per file.
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.It Li _PC_CAP_PRESENT
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Returns 1 if a capability state can be set on the specified file,
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otherwise 0.
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.It Li _PC_INF_PRESENT
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Returns 1 if an information label can be set on the specified file,
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otherwise 0.
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.It Li _PC_MAC_PRESENT
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Returns 1 if a Mandatory Access Control (MAC) label can be set on the
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specified file, otherwise 0.
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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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.Fn pathconf
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or
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.Fn 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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.Fn pathconf
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and
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.Fn fpathconf
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system calls 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 Er
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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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.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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The
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.Fn pathconf
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system call
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will fail if:
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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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.Brq Dv NAME_MAX
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characters (but see
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.Dv _PC_NO_TRUNC
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above),
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or an entire path name exceeded
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.Brq 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 ELOOP
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Too many symbolic links were encountered in translating the pathname.
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.It Bq Er EIO
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An I/O error occurred while reading from or writing to the file system.
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.El
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.Pp
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.Bl -tag -width Er
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The
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.Fn fpathconf
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system call
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will fail if:
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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 open file descriptor.
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.It Bq Er EIO
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An I/O error occurred 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 lseek 2 ,
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.Xr sysctl 3
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.Sh HISTORY
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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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system calls first appeared in
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.Bx 4.4 .
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The
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.Fn lpathconf
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system call first appeared in
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.Fx 8.0 .
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