1.\" Copyright (c) 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 4. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)pathconf.2 8.1 (Berkeley) 6/4/93 29.\" $FreeBSD$ 30.\" 31.Dd April 5, 2007 32.Dt PATHCONF 2 33.Os 34.Sh NAME 35.Nm pathconf , 36.Nm fpathconf 37.Nd get configurable pathname variables 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In unistd.h 42.Ft long 43.Fn pathconf "const char *path" "int name" 44.Ft long 45.Fn fpathconf "int fd" "int name" 46.Sh DESCRIPTION 47The 48.Fn pathconf 49and 50.Fn fpathconf 51system calls provide a method for applications to determine the current 52value of a configurable system limit or option variable associated 53with a pathname or file descriptor. 54.Pp 55For 56.Fn pathconf , 57the 58.Fa path 59argument is the name of a file or directory. 60For 61.Fn fpathconf , 62the 63.Fa fd 64argument is an open file descriptor. 65The 66.Fa name 67argument specifies the system variable to be queried. 68Symbolic constants for each name value are found in the include file 69.Li <unistd.h> . 70.Pp 71The available values are as follows: 72.Pp 73.Bl -tag -width 6n 74.Pp 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 file name. 84.It Li _PC_PATH_MAX 85The maximum number of bytes in a pathname. 86.It Li _PC_PIPE_BUF 87The maximum number of bytes which will be written atomically to a pipe. 88.It Li _PC_CHOWN_RESTRICTED 89Return 1 if appropriate privilege is required for the 90.Xr chown 2 91system call, otherwise 0. 92.St -p1003.1-2001 93requires appropriate privilege in all cases, but this behavior was optional 94in prior editions of the standard. 95.It Li _PC_NO_TRUNC 96Return greater than zero if attempts to use pathname components longer than 97.Brq Dv NAME_MAX 98will result in an 99.Bq Er ENAMETOOLONG 100error; otherwise, such components will be truncated to 101.Brq Dv NAME_MAX . 102.St -p1003.1-2001 103requires the error in all cases, but this behavior was optional in prior 104editions of the standard, and some 105.No non- Ns Tn POSIX Ns -compliant 106file systems do not support this behavior. 107.It Li _PC_VDISABLE 108Returns the terminal character disabling value. 109.It Li _PC_ASYNC_IO 110Return 1 if asynchronous I/O is supported, otherwise 0. 111.It Li _PC_PRIO_IO 112Returns 1 if prioritised I/O is supported for this file, 113otherwise 0. 114.It Li _PC_SYNC_IO 115Returns 1 if synchronised I/O is supported for this file, otherwise 0. 116.It Li _PC_ALLOC_SIZE_MIN 117Minimum number of bytes of storage allocated for any portion of a file. 118.It Li _PC_FILESIZEBITS 119Number of bits needed to represent the maximum file size. 120.It Li _PC_REC_INCR_XFER_SIZE 121Recommended increment for file transfer sizes between 122.Dv _PC_REC_MIN_XFER_SIZE 123and 124.Dv _PC_REC_MAX_XFER_SIZE . 125.It Li _PC_REC_MAX_XFER_SIZE 126Maximum recommended file transfer size. 127.It Li _PC_REC_MIN_XFER_SIZE 128Minimum recommended file transfer size. 129.It Li _PC_REC_XFER_ALIGN 130Recommended file transfer buffer alignment. 131.It Li _PC_SYMLINK_MAX 132Maximum number of bytes in a symbolic link. 133.It Li _PC_ACL_EXTENDED 134Returns 1 if an Access Control List (ACL) can be set on the specified 135file, otherwise 0. 136.It Li _PC_ACL_PATH_MAX 137Maximum number of ACL entries per file. 138.It Li _PC_CAP_PRESENT 139Returns 1 if a capability state can be set on the specified file, 140otherwise 0. 141.It Li _PC_INF_PRESENT 142Returns 1 if an information label can be set on the specified file, 143otherwise 0. 144.It Li _PC_MAC_PRESENT 145Returns 1 if a Mandatory Access Control (MAC) label can be set on the 146specified file, otherwise 0. 147.It Li _PC_MIN_HOLE_SIZE 148If a file system supports the reporting of holes (see 149.Xr lseek 2 , 150.Fn pathconf 151and 152.Fn fpathconf 153return a positive number that represents the minimum hole size returned in 154bytes. 155The offsets of holes returned will be aligned to this same value. 156A special value of 1 is returned if the file system does not specify the minimum 157hole size but still reports holes. 158.El 159.Sh RETURN VALUES 160If the call to 161.Fn pathconf 162or 163.Fn fpathconf 164is not successful, \-1 is returned and 165.Va errno 166is set appropriately. 167Otherwise, if the variable is associated with functionality that does 168not have a limit in the system, \-1 is returned and 169.Va errno 170is not modified. 171Otherwise, the current variable value is returned. 172.Sh ERRORS 173If any of the following conditions occur, the 174.Fn pathconf 175and 176.Fn fpathconf 177system calls shall return -1 and set 178.Va errno 179to the corresponding value. 180.Bl -tag -width Er 181.It Bq Er EINVAL 182The value of the 183.Fa name 184argument is invalid. 185.It Bq Er EINVAL 186The implementation does not support an association of the variable 187name with the associated file. 188.El 189.Pp 190The 191.Fn pathconf 192system call 193will fail if: 194.Bl -tag -width Er 195.It Bq Er ENOTDIR 196A component of the path prefix is not a directory. 197.It Bq Er ENAMETOOLONG 198A component of a pathname exceeded 199.Brq Dv NAME_MAX 200characters (but see 201.Dv _PC_NO_TRUNC 202above), 203or an entire path name exceeded 204.Brq Dv PATH_MAX 205characters. 206.It Bq Er ENOENT 207The named file does not exist. 208.It Bq Er EACCES 209Search permission is denied for a component of the path prefix. 210.It Bq Er ELOOP 211Too many symbolic links were encountered in translating the pathname. 212.It Bq Er EIO 213An I/O error occurred while reading from or writing to the file system. 214.El 215.Pp 216.Bl -tag -width Er 217The 218.Fn fpathconf 219system call 220will fail if: 221.It Bq Er EBADF 222The 223.Fa fd 224argument 225is not a valid open file descriptor. 226.It Bq Er EIO 227An I/O error occurred while reading from or writing to the file system. 228.El 229.Sh SEE ALSO 230.Xr lseek 2 , 231.Xr sysctl 3 232.Sh HISTORY 233The 234.Fn pathconf 235and 236.Fn fpathconf 237system calls first appeared in 238.Bx 4.4 . 239