PATHCONF(2P)PATHCONF(2P)NAME
pathconf, fpathconf - (POSIX only) get configurable pathname variables
SYNOPSIS
#include <unistd.h>
long pathconf(const char *path, int name);
long fpathconf(int fildes, int name);
DESCRIPTION
The information in this specification applies only to POSIX
applications.
The pathconf and fpathconf functions allow an application to query the
current value of a configurable limit or option (variable) associated
with a file or directory.
The pathconf function takes the name of a file or directory whose
pathname is pointed to by the path argument. The fpathconf function,
on the other hand, takes an open file descriptor as given by the fildes
argument.
The name argument represents the variable to be determined relative to
the file. The variables that may be queried by pathconf or fpathconf
and the corresponding values for the name argument are listed below:
Variable name
Value Notes
{LINK_MAX} {_PC_LINK_MAX} (1)
{MAX_CANON} {_PC_MAX_CANON} (2)
{MAX_INPUT} {_PC_MAX_INPUT} (2)
{NAME_MAX} {_PC_NAME_MAX} (3)
{PATH_MAX} {_PC_PATH_MAX} (4)
{PIPE_BUF} {_PC_PIPE_BUF} (5)
{_POSIX_CHOWN_RESTRICTED} {_PC_CHOWN_RESTRICTED} (6)
{_POSIX_NO_TRUNC} {_PC_NO_TRUNC} (3)
{_POSIX_VDISABLE} {_PC_VDISABLE} (2)
NOTES:
(1) If path or fildes refers to a directory, the value
returned applies to the directory itself.
(2) The value returned only applies to terminal files.
(3) If path or fildes refers to a directory, the value
returned applies to the filenames within the
directory.
(4) If path or fildes refers to a directory, the value
returned is the maximum length of a relative
pathname when the specified directory is the current
working directory.
(5) If path refers to a FIFO, or fildes refers to a pipe
or a FIFO, then the value returned applies to the
referenced object itself. If path or fildes refers
to a directory, then the value returned applies to
any FIFOs that exist or can be created within the
specified directory.
(6) If path or fildes refers to a directory, then the
value returned applies to terminal files that exist
or can be created within the specified directory.
The meaning of each variable is as follows:
Variable Description
{LINK_MAX} Maximum value of a file's
link count.
{MAX_CANON} Maximum number of bytes in a
terminal canonical input
line.
{MAX_INPUT} Minimum number of bytes for
which space will be available
in a terminal input queue;
therefore, the maximum number
of bytes a portable
application may require to be
typed as input before reading
them.
{NAME_MAX} Maximum number of bytes in a
file name, excluding the
terminating null.
{PATH_MAX} Maximum number of bytes in a
pathname, excluding the
terminating null.
{PIPE_BUF} Maximum number of bytes that
can written atomically when
writing to a pipe or FIFO.
{_POSIX_CHOWN_RESTRICTED} The use of chown is
restricted to super-user, and
to changing the group ID of a
file only to the effective
group ID of the process or to
one of its supplementary
group IDs.
{_POSIX_NO_TRUNC} Pathname components longer
that {NAME_MAX} generate an
error.
{_POSIX_VDISABLE} Terminal special characters
can be disabled using this
character value, if it is
defined. See tcgetattr(2P)
and tcsetattr(2P).
The values for the variables above are given in the header <limits.h>.
The symbolic constants used as values for name are given in <unistd.h>.
RETURN VALUE
Upon successful completion, both pathconf and fpathconf return the
current variable value for the file or directory without changing
errno. If the variable corresponding to name has no limit for the file
or directory, then pathconf and fpathconf return -1 without changing
errno. Otherwise, if an error condition occurs, then both functions
return -1 and change the value of errno to indicate the error.
ERRORS
If any of the following conditions occur, the pathconf and fpathconf
functions return -1 and set errno to the corresponding value:
[EINVAL] The value of name is invalid.
August 1, 1992 PATHCONF(2P)
