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.Dd August 6, 2021 29.Dt PATHCONF 2 30.Os 31.Sh NAME 32.Nm pathconf , 33.Nm lpathconf , 34.Nm fpathconf 35.Nd get configurable pathname variables 36.Sh LIBRARY 37.Lb libc 38.Sh SYNOPSIS 39.In unistd.h 40.Ft long 41.Fn pathconf "const char *path" "int name" 42.Ft long 43.Fn lpathconf "const char *path" "int name" 44.Ft long 45.Fn fpathconf "int fd" "int name" 46.Sh DESCRIPTION 47The 48.Fn pathconf , 49.Fn lpathconf 50and 51.Fn fpathconf 52system calls provide a method for applications to determine the current 53value of a configurable system limit or option variable associated 54with a pathname or file descriptor. 55.Pp 56For 57.Fn pathconf 58and 59.Fn lpathconf , 60the 61.Fa path 62argument is the name of a file or directory. 63For 64.Fn fpathconf , 65the 66.Fa fd 67argument is an open file descriptor. 68The 69.Fa name 70argument specifies the system variable to be queried. 71Symbolic constants for each name value are found in the include file 72.Li <unistd.h> . 73.Pp 74The 75.Fn lpathconf 76system call is like 77.Fn pathconf 78except in the case where the named file is a symbolic link, 79in which case 80.Fn lpathconf 81returns information about the link, 82while 83.Fn pathconf 84returns information about the file the link references. 85.Pp 86The available values are as follows: 87.Bl -tag -width 6n 88.It Li _PC_LINK_MAX 89The maximum file link count. 90.It Li _PC_MAX_CANON 91The maximum number of bytes in terminal canonical input line. 92.It Li _PC_MAX_INPUT 93The minimum maximum number of bytes for which space is available in 94a terminal input queue. 95.It Li _PC_NAME_MAX 96The maximum number of bytes in a file name. 97.It Li _PC_PATH_MAX 98The maximum number of bytes in a pathname. 99.It Li _PC_PIPE_BUF 100The maximum number of bytes which will be written atomically to a pipe. 101.It Li _PC_CHOWN_RESTRICTED 102Return 1 if appropriate privilege is required for the 103.Xr chown 2 104system call, otherwise 0. 105.St -p1003.1-2001 106requires appropriate privilege in all cases, but this behavior was optional 107in prior editions of the standard. 108.It Li _PC_NO_TRUNC 109Return greater than zero if attempts to use pathname components longer than 110.Brq Dv NAME_MAX 111will result in an 112.Bq Er ENAMETOOLONG 113error; otherwise, such components will be truncated to 114.Brq Dv NAME_MAX . 115.St -p1003.1-2001 116requires the error in all cases, but this behavior was optional in prior 117editions of the standard, and some 118.No non- Ns Tn POSIX Ns -compliant 119file systems do not support this behavior. 120.It Li _PC_VDISABLE 121Returns the terminal character disabling value. 122.It Li _PC_ASYNC_IO 123Return 1 if asynchronous I/O is supported, otherwise 0. 124.It Li _PC_PRIO_IO 125Returns 1 if prioritised I/O is supported for this file, 126otherwise 0. 127.It Li _PC_SYNC_IO 128Returns 1 if synchronised I/O is supported for this file, otherwise 0. 129.It Li _PC_ALLOC_SIZE_MIN 130Minimum number of bytes of storage allocated for any portion of a file. 131.It Li _PC_FILESIZEBITS 132Number of bits needed to represent the maximum file size. 133.It Li _PC_REC_INCR_XFER_SIZE 134Recommended increment for file transfer sizes between 135.Dv _PC_REC_MIN_XFER_SIZE 136and 137.Dv _PC_REC_MAX_XFER_SIZE . 138.It Li _PC_REC_MAX_XFER_SIZE 139Maximum recommended file transfer size. 140.It Li _PC_REC_MIN_XFER_SIZE 141Minimum recommended file transfer size. 142.It Li _PC_REC_XFER_ALIGN 143Recommended file transfer buffer alignment. 144.It Li _PC_SYMLINK_MAX 145Maximum number of bytes in a symbolic link. 146.It Li _PC_ACL_EXTENDED 147Returns 1 if an Access Control List (ACL) can be set on the specified 148file, otherwise 0. 149.It Li _PC_ACL_NFS4 150Returns 1 if an NFSv4 ACLs can be set on the specified 151file, otherwise 0. 152.It Li _PC_ACL_PATH_MAX 153Maximum number of ACL entries per file. 154.It Li _PC_CAP_PRESENT 155Returns 1 if a capability state can be set on the specified file, 156otherwise 0. 157.It Li _PC_INF_PRESENT 158Returns 1 if an information label can be set on the specified file, 159otherwise 0. 160.It Li _PC_MAC_PRESENT 161Returns 1 if a Mandatory Access Control (MAC) label can be set on the 162specified file, otherwise 0. 163.It Li _PC_MIN_HOLE_SIZE 164If a file system supports the reporting of holes (see 165.Xr lseek 2 ) , 166.Fn pathconf 167and 168.Fn fpathconf 169return a positive number that represents the minimum hole size returned in 170bytes. 171The offsets of holes returned will be aligned to this same value. 172A special value of 1 is returned if the file system does not specify the minimum 173hole size but still reports holes. 174.It Li _PC_DEALLOC_PRESENT 175Return 1 if a file system supports hole-punching (see 176.Xr fspacectl 2 ) , 177otherwise 0. 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.It Bq Er EINTEGRITY 235Corrupted data was detected while reading from the file system. 236.El 237.Pp 238The 239.Fn fpathconf 240system call 241will fail if: 242.Bl -tag -width Er 243.It Bq Er EBADF 244The 245.Fa fd 246argument 247is not a valid open file descriptor. 248.It Bq Er EIO 249An I/O error occurred while reading from or writing to the file system. 250.It Bq Er EINTEGRITY 251Corrupted data was detected while reading from the file system. 252.El 253.Sh SEE ALSO 254.Xr lseek 2 , 255.Xr sysctl 3 256.Sh HISTORY 257The 258.Fn pathconf 259and 260.Fn fpathconf 261system calls first appeared in 262.Bx 4.4 . 263The 264.Fn lpathconf 265system call first appeared in 266.Fx 8.0 . 267