1.\" $NetBSD: pathconf.2,v 1.27 2010/07/26 12:30:16 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.Pp 75.Bl -tag -width "123456" 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 0 if filenames longer than 97.Brq Dv NAME_MAX 98are silently truncated, or non-zero if an error is generated when 99.Brq Dv NAME_MAX 100is exceeded. 101.It Li _PC_VDISABLE 102Returns the terminal character disabling value. 103.It Li _PC_SYNC_IO 104Returns 1 if synchronized I/O is supported, otherwise 0. 105.It Li _PC_FILESIZEBITS 106If the maximum size file that could ever exist on the mounted file system is 107.Dv maxsize , 108then the returned value is 2 plus the floor of the base 2 logarithm of 109.Dv maxsize . 110.It Li _PC_SYMLINK_MAX 111The maximum number of bytes in a symbolic link. 112.It Li _PC_2_SYMLINKS 113When referring to a directory the system supports the creation of symbolic 114links within that directory; for nondirectory files, the meaning of 115.Dv {_PC_2_SYMLINKS} 116is undefined. 117.El 118.Sh RETURN VALUES 119If the call to 120.Nm pathconf 121or 122.Nm fpathconf 123is not successful, \-1 is returned and 124.Va errno 125is set appropriately. 126Otherwise, if the variable is associated with functionality that does 127not have a limit in the system, \-1 is returned and 128.Va errno 129is not modified. 130Otherwise, the current variable value is returned. 131.Sh ERRORS 132If any of the following conditions occur, the 133.Nm pathconf 134and 135.Nm fpathconf 136functions shall return \-1 and set 137.Va errno 138to the corresponding value. 139.Bl -tag -width Er 140.It Bq Er EINVAL 141The value of the 142.Fa name 143argument is invalid, or 144the implementation does not support an association of the variable 145name with the associated file. 146.El 147.Pp 148.Fn pathconf 149will fail if: 150.Bl -tag -width ENAMETOOLONGAA 151.It Bq Er EACCES 152Search permission is denied for a component of the path prefix. 153.It Bq Er EIO 154An I/O error occurred while reading from or writing to the file system. 155.It Bq Er ELOOP 156Too many symbolic links were encountered in translating the pathname. 157.It Bq Er ENAMETOOLONG 158A component of a pathname exceeded 255 characters, 159or an entire path name exceeded 1023 characters. 160.It Bq Er ENOENT 161The named file does not exist. 162.It Bq Er ENOTDIR 163A component of the path prefix is not a directory. 164.El 165.Pp 166.Fn fpathconf 167will fail if: 168.Bl -tag -width [EFAULT] 169.It Bq Er EBADF 170.Fa fd 171is not a valid open file descriptor. 172.It Bq Er EIO 173An I/O error occurred while reading from or writing to the file system. 174.El 175.Sh SEE ALSO 176.Xr sysctl 3 177.Sh STANDARDS 178The 179.Fn pathconf 180and 181.Fn fpathconf 182functions conform to 183.St -p1003.1-90 . 184.Sh HISTORY 185The 186.Nm pathconf 187and 188.Nm fpathconf 189functions first appeared in 190.Bx 4.4 . 191