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 July 7, 2009 32.Dt PATHCONF 2 33.Os 34.Sh NAME 35.Nm pathconf , 36.Nm lpathconf , 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 lpathconf "const char *path" "int name" 47.Ft long 48.Fn fpathconf "int fd" "int name" 49.Sh DESCRIPTION 50The 51.Fn pathconf , 52.Fn lpathconf 53and 54.Fn fpathconf 55system calls provide a method for applications to determine the current 56value of a configurable system limit or option variable associated 57with a pathname or file descriptor. 58.Pp 59For 60.Fn pathconf 61and 62.Fn lpathconf , 63the 64.Fa path 65argument is the name of a file or directory. 66For 67.Fn fpathconf , 68the 69.Fa fd 70argument is an open file descriptor. 71The 72.Fa name 73argument specifies the system variable to be queried. 74Symbolic constants for each name value are found in the include file 75.Li <unistd.h> . 76.Pp 77The 78.Fn lpathconf 79system call is like 80.Fn pathconf 81except in the case where the named file is a symbolic link, 82in which case 83.Fn lpathconf 84returns information about the link, 85while 86.Fn pathconf 87returns information about the file the link references. 88.Pp 89The available values are as follows: 90.Pp 91.Bl -tag -width 6n 92.It Li _PC_LINK_MAX 93The maximum file link count. 94.It Li _PC_MAX_CANON 95The maximum number of bytes in terminal canonical input line. 96.It Li _PC_MAX_INPUT 97The minimum maximum number of bytes for which space is available in 98a terminal input queue. 99.It Li _PC_NAME_MAX 100The maximum number of bytes in a file name. 101.It Li _PC_PATH_MAX 102The maximum number of bytes in a pathname. 103.It Li _PC_PIPE_BUF 104The maximum number of bytes which will be written atomically to a pipe. 105.It Li _PC_CHOWN_RESTRICTED 106Return 1 if appropriate privilege is required for the 107.Xr chown 2 108system call, otherwise 0. 109.St -p1003.1-2001 110requires appropriate privilege in all cases, but this behavior was optional 111in prior editions of the standard. 112.It Li _PC_NO_TRUNC 113Return greater than zero if attempts to use pathname components longer than 114.Brq Dv NAME_MAX 115will result in an 116.Bq Er ENAMETOOLONG 117error; otherwise, such components will be truncated to 118.Brq Dv NAME_MAX . 119.St -p1003.1-2001 120requires the error in all cases, but this behavior was optional in prior 121editions of the standard, and some 122.No non- Ns Tn POSIX Ns -compliant 123file systems do not support this behavior. 124.It Li _PC_VDISABLE 125Returns the terminal character disabling value. 126.It Li _PC_ASYNC_IO 127Return 1 if asynchronous I/O is supported, otherwise 0. 128.It Li _PC_PRIO_IO 129Returns 1 if prioritised I/O is supported for this file, 130otherwise 0. 131.It Li _PC_SYNC_IO 132Returns 1 if synchronised I/O is supported for this file, otherwise 0. 133.It Li _PC_ALLOC_SIZE_MIN 134Minimum number of bytes of storage allocated for any portion of a file. 135.It Li _PC_FILESIZEBITS 136Number of bits needed to represent the maximum file size. 137.It Li _PC_REC_INCR_XFER_SIZE 138Recommended increment for file transfer sizes between 139.Dv _PC_REC_MIN_XFER_SIZE 140and 141.Dv _PC_REC_MAX_XFER_SIZE . 142.It Li _PC_REC_MAX_XFER_SIZE 143Maximum recommended file transfer size. 144.It Li _PC_REC_MIN_XFER_SIZE 145Minimum recommended file transfer size. 146.It Li _PC_REC_XFER_ALIGN 147Recommended file transfer buffer alignment. 148.It Li _PC_SYMLINK_MAX 149Maximum number of bytes in a symbolic link. 150.It Li _PC_ACL_EXTENDED 151Returns 1 if an Access Control List (ACL) can be set on the specified 152file, otherwise 0. 153.It Li _PC_ACL_NFS4 154Returns 1 if an NFSv4 ACLs can be set on the specified 155file, otherwise 0. 156.It Li _PC_ACL_PATH_MAX 157Maximum number of ACL entries per file. 158.It Li _PC_CAP_PRESENT 159Returns 1 if a capability state can be set on the specified file, 160otherwise 0. 161.It Li _PC_INF_PRESENT 162Returns 1 if an information label can be set on the specified file, 163otherwise 0. 164.It Li _PC_MAC_PRESENT 165Returns 1 if a Mandatory Access Control (MAC) label can be set on the 166specified file, otherwise 0. 167.It Li _PC_MIN_HOLE_SIZE 168If a file system supports the reporting of holes (see 169.Xr lseek 2 , 170.Fn pathconf 171and 172.Fn fpathconf 173return a positive number that represents the minimum hole size returned in 174bytes. 175The offsets of holes returned will be aligned to this same value. 176A special value of 1 is returned if the file system does not specify the minimum 177hole size but still reports holes. 178.El 179.Sh RETURN VALUES 180If the call to 181.Fn pathconf 182or 183.Fn fpathconf 184is not successful, \-1 is returned and 185.Va errno 186is set appropriately. 187Otherwise, if the variable is associated with functionality that does 188not have a limit in the system, \-1 is returned and 189.Va errno 190is not modified. 191Otherwise, the current variable value is returned. 192.Sh ERRORS 193If any of the following conditions occur, the 194.Fn pathconf 195and 196.Fn fpathconf 197system calls shall return -1 and set 198.Va errno 199to the corresponding value. 200.Bl -tag -width Er 201.It Bq Er EINVAL 202The value of the 203.Fa name 204argument is invalid. 205.It Bq Er EINVAL 206The implementation does not support an association of the variable 207name with the associated file. 208.El 209.Pp 210The 211.Fn pathconf 212system call 213will fail if: 214.Bl -tag -width Er 215.It Bq Er ENOTDIR 216A component of the path prefix is not a directory. 217.It Bq Er ENAMETOOLONG 218A component of a pathname exceeded 219.Brq Dv NAME_MAX 220characters (but see 221.Dv _PC_NO_TRUNC 222above), 223or an entire path name exceeded 224.Brq Dv PATH_MAX 225characters. 226.It Bq Er ENOENT 227The named file does not exist. 228.It Bq Er EACCES 229Search permission is denied for a component of the path prefix. 230.It Bq Er ELOOP 231Too many symbolic links were encountered in translating the pathname. 232.It Bq Er EIO 233An I/O error occurred while reading from or writing to the file system. 234.El 235.Pp 236The 237.Fn fpathconf 238system call 239will fail if: 240.Bl -tag -width Er 241.It Bq Er EBADF 242The 243.Fa fd 244argument 245is not a valid open file descriptor. 246.It Bq Er EIO 247An I/O error occurred while reading from or writing to the file system. 248.El 249.Sh SEE ALSO 250.Xr lseek 2 , 251.Xr sysctl 3 252.Sh HISTORY 253The 254.Fn pathconf 255and 256.Fn fpathconf 257system calls first appeared in 258.Bx 4.4 . 259The 260.Fn lpathconf 261system call first appeared in 262.Fx 8.0 . 263