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IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)pathconf.2 8.1 (Berkeley) 6/4/93 .\" .Dd March 30, 2020 .Dt PATHCONF 2 .Os .Sh NAME .Nm pathconf , .Nm lpathconf , .Nm fpathconf .Nd get configurable pathname variables .Sh LIBRARY .Lb libc .Sh SYNOPSIS .In unistd.h .Ft long .Fn pathconf "const char *path" "int name" .Ft long .Fn lpathconf "const char *path" "int name" .Ft long .Fn fpathconf "int fd" "int name" .Sh DESCRIPTION The .Fn pathconf , .Fn lpathconf and .Fn fpathconf system calls provide a method for applications to determine the current value of a configurable system limit or option variable associated with a pathname or file descriptor. .Pp For .Fn pathconf and .Fn lpathconf , the .Fa path argument is the name of a file or directory. For .Fn fpathconf , the .Fa fd argument is an open file descriptor. The .Fa name argument specifies the system variable to be queried. Symbolic constants for each name value are found in the include file .Li . .Pp The .Fn lpathconf system call is like .Fn pathconf except in the case where the named file is a symbolic link, in which case .Fn lpathconf returns information about the link, while .Fn pathconf returns information about the file the link references. .Pp The available values are as follows: .Bl -tag -width 6n .It Li _PC_LINK_MAX The maximum file link count. .It Li _PC_MAX_CANON The maximum number of bytes in terminal canonical input line. .It Li _PC_MAX_INPUT The minimum maximum number of bytes for which space is available in a terminal input queue. .It Li _PC_NAME_MAX The maximum number of bytes in a file name. .It Li _PC_PATH_MAX The maximum number of bytes in a pathname. .It Li _PC_PIPE_BUF The maximum number of bytes which will be written atomically to a pipe. .It Li _PC_CHOWN_RESTRICTED Return 1 if appropriate privilege is required for the .Xr chown 2 system call, otherwise 0. .St -p1003.1-2001 requires appropriate privilege in all cases, but this behavior was optional in prior editions of the standard. .It Li _PC_NO_TRUNC Return greater than zero if attempts to use pathname components longer than .Brq Dv NAME_MAX will result in an .Bq Er ENAMETOOLONG error; otherwise, such components will be truncated to .Brq Dv NAME_MAX . .St -p1003.1-2001 requires the error in all cases, but this behavior was optional in prior editions of the standard, and some .No non- Ns Tn POSIX Ns -compliant file systems do not support this behavior. .It Li _PC_VDISABLE Returns the terminal character disabling value. .It Li _PC_ASYNC_IO Return 1 if asynchronous I/O is supported, otherwise 0. .It Li _PC_PRIO_IO Returns 1 if prioritised I/O is supported for this file, otherwise 0. .It Li _PC_SYNC_IO Returns 1 if synchronised I/O is supported for this file, otherwise 0. .It Li _PC_ALLOC_SIZE_MIN Minimum number of bytes of storage allocated for any portion of a file. .It Li _PC_FILESIZEBITS Number of bits needed to represent the maximum file size. .It Li _PC_REC_INCR_XFER_SIZE Recommended increment for file transfer sizes between .Dv _PC_REC_MIN_XFER_SIZE and .Dv _PC_REC_MAX_XFER_SIZE . .It Li _PC_REC_MAX_XFER_SIZE Maximum recommended file transfer size. .It Li _PC_REC_MIN_XFER_SIZE Minimum recommended file transfer size. .It Li _PC_REC_XFER_ALIGN Recommended file transfer buffer alignment. .It Li _PC_SYMLINK_MAX Maximum number of bytes in a symbolic link. .It Li _PC_ACL_EXTENDED Returns 1 if an Access Control List (ACL) can be set on the specified file, otherwise 0. .It Li _PC_ACL_NFS4 Returns 1 if an NFSv4 ACLs can be set on the specified file, otherwise 0. .It Li _PC_ACL_PATH_MAX Maximum number of ACL entries per file. .It Li _PC_CAP_PRESENT Returns 1 if a capability state can be set on the specified file, otherwise 0. .It Li _PC_INF_PRESENT Returns 1 if an information label can be set on the specified file, otherwise 0. .It Li _PC_MAC_PRESENT Returns 1 if a Mandatory Access Control (MAC) label can be set on the specified file, otherwise 0. .It Li _PC_MIN_HOLE_SIZE If a file system supports the reporting of holes (see .Xr lseek 2 ) , .Fn pathconf and .Fn fpathconf return a positive number that represents the minimum hole size returned in bytes. The offsets of holes returned will be aligned to this same value. A special value of 1 is returned if the file system does not specify the minimum hole size but still reports holes. .El .Sh RETURN VALUES If the call to .Fn pathconf or .Fn fpathconf is not successful, \-1 is returned and .Va errno is set appropriately. Otherwise, if the variable is associated with functionality that does not have a limit in the system, \-1 is returned and .Va errno is not modified. Otherwise, the current variable value is returned. .Sh ERRORS If any of the following conditions occur, the .Fn pathconf and .Fn fpathconf system calls shall return -1 and set .Va errno to the corresponding value. .Bl -tag -width Er .It Bq Er EINVAL The value of the .Fa name argument is invalid. .It Bq Er EINVAL The implementation does not support an association of the variable name with the associated file. .El .Pp The .Fn pathconf system call will fail if: .Bl -tag -width Er .It Bq Er ENOTDIR A component of the path prefix is not a directory. .It Bq Er ENAMETOOLONG A component of a pathname exceeded .Brq Dv NAME_MAX characters (but see .Dv _PC_NO_TRUNC above), or an entire path name exceeded .Brq Dv PATH_MAX characters. .It Bq Er ENOENT The named file does not exist. .It Bq Er EACCES Search permission is denied for a component of the path prefix. .It Bq Er ELOOP Too many symbolic links were encountered in translating the pathname. .It Bq Er EIO An I/O error occurred while reading from or writing to the file system. .It Bq Er EINTEGRITY Corrupted data was detected while reading from the file system. .El .Pp The .Fn fpathconf system call will fail if: .Bl -tag -width Er .It Bq Er EBADF The .Fa fd argument is not a valid open file descriptor. .It Bq Er EIO An I/O error occurred while reading from or writing to the file system. .It Bq Er EINTEGRITY Corrupted data was detected while reading from the file system. .El .Sh SEE ALSO .Xr lseek 2 , .Xr sysctl 3 .Sh HISTORY The .Fn pathconf and .Fn fpathconf system calls first appeared in .Bx 4.4 . The .Fn lpathconf system call first appeared in .Fx 8.0 .