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@(#)pathconf.2 8.1 (Berkeley) 6/4/93
.Dd June 4, 1993 .Dt PATHCONF 2 .Os BSD 4 .Sh NAME .Nm fpathconf , .Nm pathconf .Nd get configurable pathname variables .Sh SYNOPSIS .Fd #include <unistd.h> .Ft long .Fo fpathconf .Fa "int fildes" .Fa "int name" .Fc .Ft long .Fo pathconf .Fa "const char *path" .Fa "int name" .Fc .Sh DESCRIPTION
p The .Fn pathconf and .Fn fpathconf functions provides a method for applications to determine the current value of a configurable system limit or option variable associated with a pathname or file descriptor.
p For .Nm pathconf , the .Fa path argument is the name of a file or directory. For .Nm fpathconf , the .Fa fildes 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 <unistd.h> .
p The available values are as follows:
p l -tag -width "123456"
p
t Li _PC_LINK_MAX The maximum file link count.
t Li _PC_MAX_CANON The maximum number of bytes in terminal canonical input line.
t Li _PC_MAX_INPUT The minimum maximum number of bytes for which space is available in
a terminal input queue.
t Li _PC_NAME_MAX The maximum number of bytes in a file name.
t Li _PC_PATH_MAX The maximum number of bytes in a pathname.
t Li _PC_PIPE_BUF The maximum number of bytes which will be written atomically to a pipe.
t Li _PC_CHOWN_RESTRICTED Return 1 if appropriate privileges are required for the
.Xr chown 2
system call, otherwise 0.
t Li _PC_NO_TRUNC Return 1 if file names longer than KERN_NAME_MAX are truncated.
t Li _PC_VDISABLE Returns the terminal character disabling value.
t Li _PC_XATTR_SIZE_BITS Returns the number of bits used to store maximum extended
attribute size in bytes. For example, if the maximum
attribute size supported by a file system is 128K, the
value returned will be 18. However a value 18 can mean
that the maximum attribute size can be anywhere from
(256KB - 1) to 128KB. As a special case, the resource
fork can have much larger size, and some file system
specific extended attributes can have smaller and preset
size; for example, Finder Info is always 32 bytes.
.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.
l -tag -width ENAMETOOLONGAA ===========
t Bq Er EINVAL The value of the
.Fa name
argument is invalid.
===========
t Bq Er EINVAL The implementation does not support an association of the variable
name with the associated file.
.El
p
.Fn Pathconf
will fail if:
l -tag -width ENAMETOOLONGAA ===========
t Bq Er EACCES Search permission is denied for a component of the path prefix.
===========
t Bq Er EIO An I/O error occurs while reading from or writing to the file system.
===========
t Bq Er ELOOP Too many symbolic links are encountered in translating the pathname.
This is taken to be indicative of a looping symbolic link.
===========
t Bq Er ENAMETOOLONG A component of a pathname exceeded 255 characters,
or an entire path name exceeded 1023 characters.
===========
t Bq Er ENOENT The named file does not exist.
===========
t Bq Er ENOTDIR A component of the path prefix is not a directory.
.El
p
l -tag -width ENAMETOOLONGAA .Fn Fpathconf
will fail if:
===========
t Bq Er EBADF .Fa fildes
is not a valid open file descriptor.
===========
t Bq Er EIO An I/O error occurs while reading from or writing to the file system.
.El
.Sh SEE ALSO
.Xr sysctl 3
.Sh HISTORY
The
.Nm pathconf
and
.Nm fpathconf
functions first appeared in 4.4BSD.