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.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)pathconf.2 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD$ 34.\" 35.Dd November 4, 2002 36.Dt PATHCONF 2 37.Os 38.Sh NAME 39.Nm pathconf , 40.Nm fpathconf 41.Nd get configurable pathname variables 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In unistd.h 46.Ft long 47.Fn pathconf "const char *path" "int name" 48.Ft long 49.Fn fpathconf "int fd" "int name" 50.Sh DESCRIPTION 51The 52.Fn pathconf 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 , 61the 62.Fa path 63argument is the name of a file or directory. 64For 65.Fn fpathconf , 66the 67.Fa fd 68argument is an open file descriptor. 69The 70.Fa name 71argument specifies the system variable to be queried. 72Symbolic constants for each name value are found in the include file 73.Li <unistd.h> . 74.Pp 75The available values are as follows: 76.Pp 77.Bl -tag -width 6n 78.Pp 79.It Li _PC_LINK_MAX 80The maximum file link count. 81.It Li _PC_MAX_CANON 82The maximum number of bytes in terminal canonical input line. 83.It Li _PC_MAX_INPUT 84The minimum maximum number of bytes for which space is available in 85a terminal input queue. 86.It Li _PC_NAME_MAX 87The maximum number of bytes in a file name. 88.It Li _PC_PATH_MAX 89The maximum number of bytes in a pathname. 90.It Li _PC_PIPE_BUF 91The maximum number of bytes which will be written atomically to a pipe. 92.It Li _PC_CHOWN_RESTRICTED 93Return 1 if appropriate privilege is required for the 94.Xr chown 2 95system call, otherwise 0. 96.St -p1003.1-2001 97requires appropriate privilege in all cases, but this behavior was optional 98in prior editions of the standard. 99.It Li _PC_NO_TRUNC 100Return greater than zero if attempts to use pathname components longer than 101.Brq Dv NAME_MAX 102will result in an 103.Bq Er ENAMETOOLONG 104error; otherwise, such components will be truncated to 105.Brq Dv NAME_MAX . 106.St -p1003.1-2001 107requires the error in all cases, but this behavior was optional in prior 108editions of the standard, and some 109.No non- Ns Tn POSIX Ns -compliant 110file systems do not support this behavior. 111.It Li _PC_VDISABLE 112Returns the terminal character disabling value. 113.It Li _PC_ASYNC_IO 114Return 1 if asynchronous I/O is supported, otherwise 0. 115.It Li _PC_PRIO_IO 116Returns 1 if prioritised I/O is supported for this file, 117otherwise 0. 118.It Li _PC_SYNC_IO 119Returns 1 if synchronised I/O is supported for this file, otherwise 0. 120.It Li _PC_ALLOC_SIZE_MIN 121Minimum number of bytes of storage allocated for any portion of a file. 122.It Li _PC_FILESIZEBITS 123Number of bits needed to represent the maximum file size. 124.It Li _PC_REC_INCR_XFER_SIZE 125Recommended increment for file transfer sizes between 126.Dv _PC_REC_MIN_XFER_SIZE 127and 128.Dv _PC_REC_MAX_XFER_SIZE . 129.It Li _PC_REC_MAX_XFER_SIZE 130Maximum recommended file transfer size. 131.It Li _PC_REC_MIN_XFER_SIZE 132Minimum recommended file transfer size. 133.It Li _PC_REC_XFER_ALIGN 134Recommended file transfer buffer alignment. 135.It Li _PC_SYMLINK_MAX 136Maximum number of bytes in a symbolic link. 137.It Li _PC_ACL_EXTENDED 138Returns 1 if an Access Control List (ACL) can be set on the specified 139file, otherwise 0. 140.It Li _PC_ACL_PATH_MAX 141Maximum number of ACL entries per file. 142.It Li _PC_CAP_PRESENT 143Returns 1 if a capability state can be set on the specified file, 144otherwise 0. 145.It Li _PC_INF_PRESENT 146Returns 1 if an information label can be set on the specified file, 147otherwise 0. 148.It Li _PC_MAC_PRESENT 149Returns 1 if a Mandatory Access Control (MAC) label can be set on the 150specified file, otherwise 0. 151.El 152.Sh RETURN VALUES 153If the call to 154.Fn pathconf 155or 156.Fn fpathconf 157is not successful, \-1 is returned and 158.Va errno 159is set appropriately. 160Otherwise, if the variable is associated with functionality that does 161not have a limit in the system, \-1 is returned and 162.Va errno 163is not modified. 164Otherwise, the current variable value is returned. 165.Sh ERRORS 166If any of the following conditions occur, the 167.Fn pathconf 168and 169.Fn fpathconf 170system calls shall return -1 and set 171.Va errno 172to the corresponding value. 173.Bl -tag -width Er 174.It Bq Er EINVAL 175The value of the 176.Fa name 177argument is invalid. 178.It Bq Er EINVAL 179The implementation does not support an association of the variable 180name with the associated file. 181.El 182.Pp 183The 184.Fn pathconf 185system call 186will fail if: 187.Bl -tag -width Er 188.It Bq Er ENOTDIR 189A component of the path prefix is not a directory. 190.It Bq Er ENAMETOOLONG 191A component of a pathname exceeded 192.Brq Dv NAME_MAX 193characters (but see 194.Dv _PC_NO_TRUNC 195above), 196or an entire path name exceeded 197.Brq Dv PATH_MAX 198characters. 199.It Bq Er ENOENT 200The named file does not exist. 201.It Bq Er EACCES 202Search permission is denied for a component of the path prefix. 203.It Bq Er ELOOP 204Too many symbolic links were encountered in translating the pathname. 205.It Bq Er EIO 206An I/O error occurred while reading from or writing to the file system. 207.El 208.Pp 209.Bl -tag -width Er 210The 211.Fn fpathconf 212system call 213will fail if: 214.It Bq Er EBADF 215The 216.Fa fd 217argument 218is not a valid open file descriptor. 219.It Bq Er EIO 220An I/O error occurred while reading from or writing to the file system. 221.El 222.Sh SEE ALSO 223.Xr sysctl 3 224.Sh HISTORY 225The 226.Fn pathconf 227and 228.Fn fpathconf 229system calls first appeared in 230.Bx 4.4 . 231