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.\" 30.Dd August 6, 2021 31.Dt PATHCONF 2 32.Os 33.Sh NAME 34.Nm pathconf , 35.Nm lpathconf , 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 lpathconf "const char *path" "int name" 46.Ft long 47.Fn fpathconf "int fd" "int name" 48.Sh DESCRIPTION 49The 50.Fn pathconf , 51.Fn lpathconf 52and 53.Fn fpathconf 54system calls provide a method for applications to determine the current 55value of a configurable system limit or option variable associated 56with a pathname or file descriptor. 57.Pp 58For 59.Fn pathconf 60and 61.Fn lpathconf , 62the 63.Fa path 64argument is the name of a file or directory. 65For 66.Fn fpathconf , 67the 68.Fa fd 69argument is an open file descriptor. 70The 71.Fa name 72argument specifies the system variable to be queried. 73Symbolic constants for each name value are found in the include file 74.Li <unistd.h> . 75.Pp 76The 77.Fn lpathconf 78system call is like 79.Fn pathconf 80except in the case where the named file is a symbolic link, 81in which case 82.Fn lpathconf 83returns information about the link, 84while 85.Fn pathconf 86returns information about the file the link references. 87.Pp 88The available values are as follows: 89.Bl -tag -width 6n 90.It Li _PC_LINK_MAX 91The maximum file link count. 92.It Li _PC_MAX_CANON 93The maximum number of bytes in terminal canonical input line. 94.It Li _PC_MAX_INPUT 95The minimum maximum number of bytes for which space is available in 96a terminal input queue. 97.It Li _PC_NAME_MAX 98The maximum number of bytes in a file name. 99.It Li _PC_PATH_MAX 100The maximum number of bytes in a pathname. 101.It Li _PC_PIPE_BUF 102The maximum number of bytes which will be written atomically to a pipe. 103.It Li _PC_CHOWN_RESTRICTED 104Return 1 if appropriate privilege is required for the 105.Xr chown 2 106system call, otherwise 0. 107.St -p1003.1-2001 108requires appropriate privilege in all cases, but this behavior was optional 109in prior editions of the standard. 110.It Li _PC_NO_TRUNC 111Return greater than zero if attempts to use pathname components longer than 112.Brq Dv NAME_MAX 113will result in an 114.Bq Er ENAMETOOLONG 115error; otherwise, such components will be truncated to 116.Brq Dv NAME_MAX . 117.St -p1003.1-2001 118requires the error in all cases, but this behavior was optional in prior 119editions of the standard, and some 120.No non- Ns Tn POSIX Ns -compliant 121file systems do not support this behavior. 122.It Li _PC_VDISABLE 123Returns the terminal character disabling value. 124.It Li _PC_ASYNC_IO 125Return 1 if asynchronous I/O is supported, otherwise 0. 126.It Li _PC_PRIO_IO 127Returns 1 if prioritised I/O is supported for this file, 128otherwise 0. 129.It Li _PC_SYNC_IO 130Returns 1 if synchronised I/O is supported for this file, otherwise 0. 131.It Li _PC_ALLOC_SIZE_MIN 132Minimum number of bytes of storage allocated for any portion of a file. 133.It Li _PC_FILESIZEBITS 134Number of bits needed to represent the maximum file size. 135.It Li _PC_REC_INCR_XFER_SIZE 136Recommended increment for file transfer sizes between 137.Dv _PC_REC_MIN_XFER_SIZE 138and 139.Dv _PC_REC_MAX_XFER_SIZE . 140.It Li _PC_REC_MAX_XFER_SIZE 141Maximum recommended file transfer size. 142.It Li _PC_REC_MIN_XFER_SIZE 143Minimum recommended file transfer size. 144.It Li _PC_REC_XFER_ALIGN 145Recommended file transfer buffer alignment. 146.It Li _PC_SYMLINK_MAX 147Maximum number of bytes in a symbolic link. 148.It Li _PC_ACL_EXTENDED 149Returns 1 if an Access Control List (ACL) can be set on the specified 150file, otherwise 0. 151.It Li _PC_ACL_NFS4 152Returns 1 if an NFSv4 ACLs can be set on the specified 153file, otherwise 0. 154.It Li _PC_ACL_PATH_MAX 155Maximum number of ACL entries per file. 156.It Li _PC_CAP_PRESENT 157Returns 1 if a capability state can be set on the specified file, 158otherwise 0. 159.It Li _PC_INF_PRESENT 160Returns 1 if an information label can be set on the specified file, 161otherwise 0. 162.It Li _PC_MAC_PRESENT 163Returns 1 if a Mandatory Access Control (MAC) label can be set on the 164specified file, otherwise 0. 165.It Li _PC_MIN_HOLE_SIZE 166If a file system supports the reporting of holes (see 167.Xr lseek 2 ) , 168.Fn pathconf 169and 170.Fn fpathconf 171return a positive number that represents the minimum hole size returned in 172bytes. 173The offsets of holes returned will be aligned to this same value. 174A special value of 1 is returned if the file system does not specify the minimum 175hole size but still reports holes. 176.It Li _PC_DEALLOC_PRESENT 177Return 1 if a file system supports hole-punching (see 178.Xr fspacectl 2 ) , 179otherwise 0. 180.El 181.Sh RETURN VALUES 182If the call to 183.Fn pathconf 184or 185.Fn fpathconf 186is not successful, \-1 is returned and 187.Va errno 188is set appropriately. 189Otherwise, if the variable is associated with functionality that does 190not have a limit in the system, \-1 is returned and 191.Va errno 192is not modified. 193Otherwise, the current variable value is returned. 194.Sh ERRORS 195If any of the following conditions occur, the 196.Fn pathconf 197and 198.Fn fpathconf 199system calls shall return -1 and set 200.Va errno 201to the corresponding value. 202.Bl -tag -width Er 203.It Bq Er EINVAL 204The value of the 205.Fa name 206argument is invalid. 207.It Bq Er EINVAL 208The implementation does not support an association of the variable 209name with the associated file. 210.El 211.Pp 212The 213.Fn pathconf 214system call 215will fail if: 216.Bl -tag -width Er 217.It Bq Er ENOTDIR 218A component of the path prefix is not a directory. 219.It Bq Er ENAMETOOLONG 220A component of a pathname exceeded 221.Brq Dv NAME_MAX 222characters (but see 223.Dv _PC_NO_TRUNC 224above), 225or an entire path name exceeded 226.Brq Dv PATH_MAX 227characters. 228.It Bq Er ENOENT 229The named file does not exist. 230.It Bq Er EACCES 231Search permission is denied for a component of the path prefix. 232.It Bq Er ELOOP 233Too many symbolic links were encountered in translating the pathname. 234.It Bq Er EIO 235An I/O error occurred while reading from or writing to the file system. 236.It Bq Er EINTEGRITY 237Corrupted data was detected while reading from the file system. 238.El 239.Pp 240The 241.Fn fpathconf 242system call 243will fail if: 244.Bl -tag -width Er 245.It Bq Er EBADF 246The 247.Fa fd 248argument 249is not a valid open file descriptor. 250.It Bq Er EIO 251An I/O error occurred while reading from or writing to the file system. 252.It Bq Er EINTEGRITY 253Corrupted data was detected while reading from the file system. 254.El 255.Sh SEE ALSO 256.Xr lseek 2 , 257.Xr sysctl 3 258.Sh HISTORY 259The 260.Fn pathconf 261and 262.Fn fpathconf 263system calls first appeared in 264.Bx 4.4 . 265The 266.Fn lpathconf 267system call first appeared in 268.Fx 8.0 . 269