.\"	$OpenBSD: pathconf.2,v 1.10 2003/02/27 07:55:34 jmc Exp $
.\"	$NetBSD: pathconf.2,v 1.2 1995/02/27 12:35:22 cgd Exp $
.\"
.\" Copyright (c) 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
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.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\"	@(#)pathconf.2	8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.Dt PATHCONF 2
.Os
.Sh NAME
.Nm pathconf ,
.Nm fpathconf
.Nd get configurable pathname variables
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft long
.Fn pathconf "const char *path" "int name"
.Ft long
.Fn fpathconf "int fd" "int name"
.Sh DESCRIPTION
The
.Fn pathconf
and
.Fn fpathconf
functions provides a method for applications to determine the current
value of a configurable system limit or option variable associated
with a pathname or file descriptor.
.Pp
For
.Nm pathconf ,
the
.Fa path
argument is the name of a file or directory.
For
.Nm fpathconf ,
the
.Fa fd
argument is an open file descriptor.
The
.Fa name
argument specifies the system variable to be queried.
Symbolic constants for each name value are found in the include file
.Aq Pa unistd.h .
.Pp
The available values are as follows:
.Pp
.Bl -tag -width "123456"
.Pp
.It Dv _PC_LINK_MAX
The maximum file link count.
.It Dv _PC_MAX_CANON
The maximum number of bytes in a terminal canonical input line.
.It Dv _PC_MAX_INPUT
The maximum number of bytes for which space is available in
a terminal input queue.
.It Dv _PC_NAME_MAX
The maximum number of bytes in a file name.
.It Dv _PC_PATH_MAX
The maximum number of bytes in a pathname.
.It Dv _PC_PIPE_BUF
The maximum number of bytes which will be written atomically to a pipe.
.It Dv _PC_CHOWN_RESTRICTED
Return 1 if appropriate privileges are required for the
.Xr chown 2
system call, otherwise 0.
.It Dv _PC_NO_TRUNC
Return 1 if file names longer than
.Dv KERN_NAME_MAX
are truncated.
.It Dv _PC_VDISABLE
Returns the terminal character disabling value.
.El
.Sh RETURN VALUES
If the call to
.Nm pathconf
or
.Nm fpathconf
is not successful, \-1 is returned and
.Va errno
is set appropriately.
Otherwise, if the variable is associated with functionality that does
not have a limit in the system, \-1 is returned and
.Va errno
is not modified.
Otherwise, the current variable value is returned.
.Sh ERRORS
If any of the following conditions occur, the
.Nm pathconf
and
.Nm fpathconf
functions shall return \-1 and set
.Va errno
to the corresponding value.
.Bl -tag -width Er
.It Bq Er EINVAL
The value of the
.Fa name
argument is invalid.
.It Bq Er EINVAL
The implementation does not support an association of the variable
name with the associated file.
.El
.Fn pathconf
will fail if:
.Bl -tag -width ENAMETOOLONGAA
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.It Bq Er ENAMETOOLONG
A component of a pathname exceeded 255 characters,
or an entire path name exceeded 1023 characters.
.It Bq Er ENOENT
The named file does not exist.
.It Bq Er EACCES
Search permission is denied for a component of the path prefix.
.It Bq Er ELOOP
Too many symbolic links were encountered in translating the pathname.
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.El
.Pp
.Bl -tag -width [EFAULT]
.Fn fpathconf
will fail if:
.It Bq Er EBADF
.Fa fd
is not a valid open file descriptor.
.It Bq Er EIO
An I/O error occurred while reading from or writing to the file system.
.El
.Sh SEE ALSO
.Xr sysctl 3
.Sh HISTORY
The
.Nm pathconf
and
.Nm fpathconf
functions first appeared in
.Bx 4.4 .