1.\" $NetBSD: pathconf.2,v 1.28 2014/06/09 09:15:48 njoly Exp $ 2.\" 3.\" Copyright (c) 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)pathconf.2 8.1 (Berkeley) 6/4/93 31.\" 32.Dd July 26, 2010 33.Dt PATHCONF 2 34.Os 35.Sh NAME 36.Nm pathconf , 37.Nm fpathconf 38.Nd get configurable pathname variables 39.Sh LIBRARY 40.Lb libc 41.Sh SYNOPSIS 42.In unistd.h 43.Ft long 44.Fn pathconf "const char *path" "int name" 45.Ft long 46.Fn fpathconf "int fd" "int name" 47.Sh DESCRIPTION 48The 49.Fn pathconf 50and 51.Fn fpathconf 52functions provide a method for applications to determine the current 53value of a configurable system limit or option variable associated 54with a pathname or file descriptor. 55.Pp 56For 57.Nm pathconf , 58the 59.Fa path 60argument is the name of a file or directory. 61For 62.Nm fpathconf , 63the 64.Fa fd 65argument is an open file descriptor. 66The 67.Fa name 68argument specifies the system variable to be queried. 69Symbolic constants for each name value are found in the 70.In unistd.h 71header. 72.Pp 73The available values are as follows: 74.Bl -tag -width "123456" 75.It Li _PC_LINK_MAX 76The maximum file link count. 77.It Li _PC_MAX_CANON 78The maximum number of bytes in terminal canonical input line. 79.It Li _PC_MAX_INPUT 80The minimum maximum number of bytes for which space is available in 81a terminal input queue. 82.It Li _PC_NAME_MAX 83The maximum number of bytes in a filename, 84not including a terminating null character. 85.It Li _PC_PATH_MAX 86The maximum number of bytes in a pathname, 87including the terminating null character. 88.It Li _PC_PIPE_BUF 89The maximum number of bytes which will be written atomically to a pipe. 90.It Li _PC_CHOWN_RESTRICTED 91Return 1 if appropriate privileges are required for the 92.Xr chown 2 93system call, otherwise 0. 94.It Li _PC_NO_TRUNC 95Return 0 if filenames longer than 96.Brq Dv NAME_MAX 97are silently truncated, or non-zero if an error is generated when 98.Brq Dv NAME_MAX 99is exceeded. 100.It Li _PC_VDISABLE 101Returns the terminal character disabling value. 102.It Li _PC_SYNC_IO 103Returns 1 if synchronized I/O is supported, otherwise 0. 104.It Li _PC_FILESIZEBITS 105If the maximum size file that could ever exist on the mounted file system is 106.Dv maxsize , 107then the returned value is 2 plus the floor of the base 2 logarithm of 108.Dv maxsize . 109.It Li _PC_SYMLINK_MAX 110The maximum number of bytes in a symbolic link. 111.It Li _PC_2_SYMLINKS 112When referring to a directory the system supports the creation of symbolic 113links within that directory; for nondirectory files, the meaning of 114.Dv {_PC_2_SYMLINKS} 115is undefined. 116.El 117.Sh RETURN VALUES 118If the call to 119.Nm pathconf 120or 121.Nm fpathconf 122is not successful, \-1 is returned and 123.Va errno 124is set appropriately. 125Otherwise, if the variable is associated with functionality that does 126not have a limit in the system, \-1 is returned and 127.Va errno 128is not modified. 129Otherwise, the current variable value is returned. 130.Sh ERRORS 131If any of the following conditions occur, the 132.Nm pathconf 133and 134.Nm fpathconf 135functions shall return \-1 and set 136.Va errno 137to the corresponding value. 138.Bl -tag -width Er 139.It Bq Er EINVAL 140The value of the 141.Fa name 142argument is invalid, or 143the implementation does not support an association of the variable 144name with the associated file. 145.El 146.Pp 147.Fn pathconf 148will fail if: 149.Bl -tag -width ENAMETOOLONGAA 150.It Bq Er EACCES 151Search permission is denied for a component of the path prefix. 152.It Bq Er EIO 153An I/O error occurred while reading from or writing to the file system. 154.It Bq Er ELOOP 155Too many symbolic links were encountered in translating the pathname. 156.It Bq Er ENAMETOOLONG 157A component of a pathname exceeded 158.Brq Dv NAME_MAX 159characters, or an entire path name exceeded 160.Brq Dv PATH_MAX 161characters. 162.It Bq Er ENOENT 163The named file does not exist. 164.It Bq Er ENOTDIR 165A component of the path prefix is not a directory. 166.El 167.Pp 168.Fn fpathconf 169will fail if: 170.Bl -tag -width [EFAULT] 171.It Bq Er EBADF 172.Fa fd 173is not a valid open file descriptor. 174.It Bq Er EIO 175An I/O error occurred while reading from or writing to the file system. 176.El 177.Sh SEE ALSO 178.Xr sysctl 3 179.Sh STANDARDS 180The 181.Fn pathconf 182and 183.Fn fpathconf 184functions conform to 185.St -p1003.1-90 . 186.Sh HISTORY 187The 188.Nm pathconf 189and 190.Nm fpathconf 191functions first appeared in 192.Bx 4.4 . 193