1.\" $NetBSD: pathconf.2,v 1.21 2008/08/14 18:00:08 wiz 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.Pp 76.It Li _PC_LINK_MAX 77The maximum file link count. 78.It Li _PC_MAX_CANON 79The maximum number of bytes in terminal canonical input line. 80.It Li _PC_MAX_INPUT 81The minimum maximum number of bytes for which space is available in 82a terminal input queue. 83.It Li _PC_NAME_MAX 84The maximum number of bytes in a filename, 85not including a terminating null character. 86.It Li _PC_PATH_MAX 87The maximum number of bytes in a pathname, 88including the terminating null character. 89.It Li _PC_PIPE_BUF 90The maximum number of bytes which will be written atomically to a pipe. 91.It Li _PC_CHOWN_RESTRICTED 92Return 1 if appropriate privileges are required for the 93.Xr chown 2 94system call, otherwise 0. 95.It Li _PC_NO_TRUNC 96Return 1 if filenames longer than 97.Dv {NAME_MAX} 98are truncated. 99.It Li _PC_VDISABLE 100Returns the terminal character disabling value. 101.It Li _PC_SYNC_IO 102Returns 1 if synchronized I/O is supported, otherwise 0. 103.It Li _PC_FILESIZEBITS 104If the maximum size file that could ever exist on the mounted file system is 105.Dv maxsize , 106then the returned value is 2 plus the floor of the base 2 logarithm of 107.Dv maxsize . 108.It Li _PC_SYMLINK_MAX 109The maximum number of bytes in a symbolic link. 110.It Li _PC_2_SYMLINKS 111When referring to a directory the system supports the creation of symbolic 112links within that directory; for nondirectory files, the meaning of 113.Dv {_PC_2_SYMLINKS} 114is undefined. 115.El 116.Sh RETURN VALUES 117If the call to 118.Nm pathconf 119or 120.Nm fpathconf 121is not successful, \-1 is returned and 122.Va errno 123is set appropriately. 124Otherwise, if the variable is associated with functionality that does 125not have a limit in the system, \-1 is returned and 126.Va errno 127is not modified. 128Otherwise, the current variable value is returned. 129.Sh ERRORS 130If any of the following conditions occur, the 131.Nm pathconf 132and 133.Nm fpathconf 134functions shall return \-1 and set 135.Va errno 136to the corresponding value. 137.Bl -tag -width Er 138.It Bq Er EINVAL 139The value of the 140.Fa name 141argument is invalid, or 142the implementation does not support an association of the variable 143name with the associated file. 144.El 145.Pp 146.Fn pathconf 147will fail if: 148.Bl -tag -width ENAMETOOLONGAA 149.It Bq Er EACCES 150Search permission is denied for a component of the path prefix. 151.It Bq Er EIO 152An I/O error occurred while reading from or writing to the file system. 153.It Bq Er ELOOP 154Too many symbolic links were encountered in translating the pathname. 155.It Bq Er ENAMETOOLONG 156A component of a pathname exceeded 255 characters, 157or an entire path name exceeded 1023 characters. 158.It Bq Er ENOENT 159The named file does not exist. 160.It Bq Er ENOTDIR 161A component of the path prefix is not a directory. 162.El 163.Pp 164.Bl -tag -width [EFAULT] 165.Fn fpathconf 166will fail if: 167.It Bq Er EBADF 168.Fa fd 169is not a valid open file descriptor. 170.It Bq Er EIO 171An I/O error occurred while reading from or writing to the file system. 172.El 173.Sh SEE ALSO 174.Xr sysctl 3 175.Sh STANDARDS 176The 177.Fn pathconf 178and 179.Fn fpathconf 180functions conform to 181.St -p1003.1-90 . 182.Sh HISTORY 183The 184.Nm pathconf 185and 186.Nm fpathconf 187functions first appeared in 188.Bx 4.4 . 189