1.\" $NetBSD: pathconf.2,v 1.22 2009/03/11 13:39:14 joerg 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 August 14, 2008 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 include file 70.Li \*[Lt]unistd.h\*[Gt] . 71.Pp 72The available values are as follows: 73.Pp 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 1 if filenames longer than 96.Dv {NAME_MAX} 97are truncated. 98.It Li _PC_VDISABLE 99Returns the terminal character disabling value. 100.It Li _PC_SYNC_IO 101Returns 1 if synchronized I/O is supported, otherwise 0. 102.It Li _PC_FILESIZEBITS 103If the maximum size file that could ever exist on the mounted file system is 104.Dv maxsize , 105then the returned value is 2 plus the floor of the base 2 logarithm of 106.Dv maxsize . 107.It Li _PC_SYMLINK_MAX 108The maximum number of bytes in a symbolic link. 109.It Li _PC_2_SYMLINKS 110When referring to a directory the system supports the creation of symbolic 111links within that directory; for nondirectory files, the meaning of 112.Dv {_PC_2_SYMLINKS} 113is undefined. 114.El 115.Sh RETURN VALUES 116If the call to 117.Nm pathconf 118or 119.Nm fpathconf 120is not successful, \-1 is returned and 121.Va errno 122is set appropriately. 123Otherwise, if the variable is associated with functionality that does 124not have a limit in the system, \-1 is returned and 125.Va errno 126is not modified. 127Otherwise, the current variable value is returned. 128.Sh ERRORS 129If any of the following conditions occur, the 130.Nm pathconf 131and 132.Nm fpathconf 133functions shall return \-1 and set 134.Va errno 135to the corresponding value. 136.Bl -tag -width Er 137.It Bq Er EINVAL 138The value of the 139.Fa name 140argument is invalid, or 141the implementation does not support an association of the variable 142name with the associated file. 143.El 144.Pp 145.Fn pathconf 146will fail if: 147.Bl -tag -width ENAMETOOLONGAA 148.It Bq Er EACCES 149Search permission is denied for a component of the path prefix. 150.It Bq Er EIO 151An I/O error occurred while reading from or writing to the file system. 152.It Bq Er ELOOP 153Too many symbolic links were encountered in translating the pathname. 154.It Bq Er ENAMETOOLONG 155A component of a pathname exceeded 255 characters, 156or an entire path name exceeded 1023 characters. 157.It Bq Er ENOENT 158The named file does not exist. 159.It Bq Er ENOTDIR 160A component of the path prefix is not a directory. 161.El 162.Pp 163.Fn fpathconf 164will fail if: 165.Bl -tag -width [EFAULT] 166.It Bq Er EBADF 167.Fa fd 168is not a valid open file descriptor. 169.It Bq Er EIO 170An I/O error occurred while reading from or writing to the file system. 171.El 172.Sh SEE ALSO 173.Xr sysctl 3 174.Sh STANDARDS 175The 176.Fn pathconf 177and 178.Fn fpathconf 179functions conform to 180.St -p1003.1-90 . 181.Sh HISTORY 182The 183.Nm pathconf 184and 185.Nm fpathconf 186functions first appeared in 187.Bx 4.4 . 188