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. 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 March 30, 2020 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.Bl -tag -width 6n 91.It Li _PC_LINK_MAX 92The maximum file link count. 93.It Li _PC_MAX_CANON 94The maximum number of bytes in terminal canonical input line. 95.It Li _PC_MAX_INPUT 96The minimum maximum number of bytes for which space is available in 97a terminal input queue. 98.It Li _PC_NAME_MAX 99The maximum number of bytes in a file name. 100.It Li _PC_PATH_MAX 101The maximum number of bytes in a pathname. 102.It Li _PC_PIPE_BUF 103The maximum number of bytes which will be written atomically to a pipe. 104.It Li _PC_CHOWN_RESTRICTED 105Return 1 if appropriate privilege is required for the 106.Xr chown 2 107system call, otherwise 0. 108.St -p1003.1-2001 109requires appropriate privilege in all cases, but this behavior was optional 110in prior editions of the standard. 111.It Li _PC_NO_TRUNC 112Return greater than zero if attempts to use pathname components longer than 113.Brq Dv NAME_MAX 114will result in an 115.Bq Er ENAMETOOLONG 116error; otherwise, such components will be truncated to 117.Brq Dv NAME_MAX . 118.St -p1003.1-2001 119requires the error in all cases, but this behavior was optional in prior 120editions of the standard, and some 121.No non- Ns Tn POSIX Ns -compliant 122file systems do not support this behavior. 123.It Li _PC_VDISABLE 124Returns the terminal character disabling value. 125.It Li _PC_ASYNC_IO 126Return 1 if asynchronous I/O is supported, otherwise 0. 127.It Li _PC_PRIO_IO 128Returns 1 if prioritised I/O is supported for this file, 129otherwise 0. 130.It Li _PC_SYNC_IO 131Returns 1 if synchronised I/O is supported for this file, otherwise 0. 132.It Li _PC_ALLOC_SIZE_MIN 133Minimum number of bytes of storage allocated for any portion of a file. 134.It Li _PC_FILESIZEBITS 135Number of bits needed to represent the maximum file size. 136.It Li _PC_REC_INCR_XFER_SIZE 137Recommended increment for file transfer sizes between 138.Dv _PC_REC_MIN_XFER_SIZE 139and 140.Dv _PC_REC_MAX_XFER_SIZE . 141.It Li _PC_REC_MAX_XFER_SIZE 142Maximum recommended file transfer size. 143.It Li _PC_REC_MIN_XFER_SIZE 144Minimum recommended file transfer size. 145.It Li _PC_REC_XFER_ALIGN 146Recommended file transfer buffer alignment. 147.It Li _PC_SYMLINK_MAX 148Maximum number of bytes in a symbolic link. 149.It Li _PC_ACL_EXTENDED 150Returns 1 if an Access Control List (ACL) can be set on the specified 151file, otherwise 0. 152.It Li _PC_ACL_NFS4 153Returns 1 if an NFSv4 ACLs can be set on the specified 154file, otherwise 0. 155.It Li _PC_ACL_PATH_MAX 156Maximum number of ACL entries per file. 157.It Li _PC_CAP_PRESENT 158Returns 1 if a capability state can be set on the specified file, 159otherwise 0. 160.It Li _PC_INF_PRESENT 161Returns 1 if an information label can be set on the specified file, 162otherwise 0. 163.It Li _PC_MAC_PRESENT 164Returns 1 if a Mandatory Access Control (MAC) label can be set on the 165specified file, otherwise 0. 166.It Li _PC_MIN_HOLE_SIZE 167If a file system supports the reporting of holes (see 168.Xr lseek 2 ) , 169.Fn pathconf 170and 171.Fn fpathconf 172return a positive number that represents the minimum hole size returned in 173bytes. 174The offsets of holes returned will be aligned to this same value. 175A special value of 1 is returned if the file system does not specify the minimum 176hole size but still reports holes. 177.El 178.Sh RETURN VALUES 179If the call to 180.Fn pathconf 181or 182.Fn fpathconf 183is not successful, \-1 is returned and 184.Va errno 185is set appropriately. 186Otherwise, if the variable is associated with functionality that does 187not have a limit in the system, \-1 is returned and 188.Va errno 189is not modified. 190Otherwise, the current variable value is returned. 191.Sh ERRORS 192If any of the following conditions occur, the 193.Fn pathconf 194and 195.Fn fpathconf 196system calls shall return -1 and set 197.Va errno 198to the corresponding value. 199.Bl -tag -width Er 200.It Bq Er EINVAL 201The value of the 202.Fa name 203argument is invalid. 204.It Bq Er EINVAL 205The implementation does not support an association of the variable 206name with the associated file. 207.El 208.Pp 209The 210.Fn pathconf 211system call 212will fail if: 213.Bl -tag -width Er 214.It Bq Er ENOTDIR 215A component of the path prefix is not a directory. 216.It Bq Er ENAMETOOLONG 217A component of a pathname exceeded 218.Brq Dv NAME_MAX 219characters (but see 220.Dv _PC_NO_TRUNC 221above), 222or an entire path name exceeded 223.Brq Dv PATH_MAX 224characters. 225.It Bq Er ENOENT 226The named file does not exist. 227.It Bq Er EACCES 228Search permission is denied for a component of the path prefix. 229.It Bq Er ELOOP 230Too many symbolic links were encountered in translating the pathname. 231.It Bq Er EIO 232An I/O error occurred while reading from or writing to the file system. 233.It Bq Er EINTEGRITY 234Corrupted data was detected while reading from the file system. 235.El 236.Pp 237The 238.Fn fpathconf 239system call 240will fail if: 241.Bl -tag -width Er 242.It Bq Er EBADF 243The 244.Fa fd 245argument 246is not a valid open file descriptor. 247.It Bq Er EIO 248An I/O error occurred while reading from or writing to the file system. 249.It Bq Er EINTEGRITY 250Corrupted data was detected while reading from the file system. 251.El 252.Sh SEE ALSO 253.Xr lseek 2 , 254.Xr sysctl 3 255.Sh HISTORY 256The 257.Fn pathconf 258and 259.Fn fpathconf 260system calls first appeared in 261.Bx 4.4 . 262The 263.Fn lpathconf 264system call first appeared in 265.Fx 8.0 . 266