.\" $OpenBSD: pathconf.2,v 1.20 2013/03/28 20:37:56 jmc Exp $ .\" $NetBSD: pathconf.2,v 1.2 1995/02/27 12:35:22 cgd Exp $ .\" .\" Copyright (c) 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. 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 $Mdocdate: March 28 2013 $ .Dt PATHCONF 2 .Os .Sh NAME .Nm pathconf , .Nm fpathconf .Nd get configurable pathname variables .Sh SYNOPSIS .Fd #include .Ft long .Fn pathconf "const char *path" "int name" .Ft long .Fn fpathconf "int fd" "int name" .Sh DESCRIPTION The .Fn pathconf and .Fn fpathconf functions 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 .Nm pathconf , the .Fa path argument is the name of a file or directory. For .Nm 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 .Aq Pa unistd.h . .Pp The available values are as follows: .Bl -tag -width "123456" .It Dv _PC_LINK_MAX The maximum file link count. .It Dv _PC_MAX_CANON The maximum number of bytes in a terminal canonical input line. .It Dv _PC_MAX_INPUT The maximum number of bytes for which space is available in a terminal input queue. .It Dv _PC_NAME_MAX The maximum number of bytes in a file name. .It Dv _PC_PATH_MAX The maximum number of bytes in a pathname. .It Dv _PC_PIPE_BUF The maximum number of bytes which will be written atomically to a pipe. .It Dv _PC_CHOWN_RESTRICTED Returns 1 if appropriate privileges are 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 Dv _PC_NO_TRUNC Returns 1 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 non-POSIX-compliant file systems do not support this behavior. .It Dv _PC_VDISABLE Returns the terminal character disabling value. .It Dv _PC_2_SYMLINKS Returns 1 if the filesystem supports the creation of symbolic links within the specified directory; the meaning of .Dv _PC_2_SYMLINKS is unspecified for non-directory files. .It Dv _PC_ALLOC_SIZE_MIN Minimum number of bytes of storage allocated for any portion of a file. .It Dv _PC_ASYNC_IO Returns 1 if asynchronous I/O is supported, otherwise 0. .It Dv _PC_FILESIZEBITS Number of bits needed to represent the maximum file size. .It Dv _PC_PRIO_IO Returns 1 if prioritized I/O is supported, otherwise 0. .It Dv _PC_REC_INCR_XFER_SIZE Recommended increment for file transfer sizes between _PC_REC_MIN_XFER_SIZE and _PC_REC_MAX_XFER_SIZE. .It Dv _PC_REC_MAX_XFER_SIZE Maximum recommended file transfer size. .It Dv _PC_REC_MIN_XFER_SIZE Minimum recommended file transfer size. .It Dv _PC_REC_XFER_ALIGN Recommended file transfer buffer alignment. .It Dv _PC_SYMLINK_MAX Maximum number of bytes in a symbolic link. .It Dv _PC_SYNC_IO Returns 1 if synchronized I/O is supported, otherwise 0. .It Dv _PC_TIMESTAMP_RESOLUTION The resolution in nanoseconds of file timestamps. .El .Sh RETURN VALUES If the call to .Nm pathconf or .Nm 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 .Nm pathconf and .Nm fpathconf functions 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. .It Bq Er EIO An I/O error occurred while reading from the file system. .El .Pp .Fn pathconf 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 EFAULT .Fa path points outside the process's allocated address space. .El .Pp .Fn fpathconf will fail if: .Bl -tag -width Er .It Bq Er EBADF .Fa fd is not a valid open file descriptor. .El .Sh SEE ALSO .Xr sysconf 3 , .Xr sysctl 3 .Sh STANDARDS The .Nm pathconf and .Nm fpathconf functions conform to .St -p1003.1-2008 . .Sh HISTORY The .Nm pathconf and .Nm fpathconf functions first appeared in .Bx 4.4 .