The
pathconf(),
lpathconf()
and
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.
For
pathconf()
and
lpathconf(),
the
path
argument is the name of a file or directory.
For
fpathconf(),
the
fd
argument is an open file descriptor.
The
name
argument specifies the system variable to be queried.
Symbolic constants for each name value are found in the include file
<unistd.h>.
The
lpathconf()
system call is like
pathconf()
except in the case where the named file is a symbolic link,
in which case
lpathconf()
returns information about the link,
while
pathconf()
returns information about the file the link references.
The available values are as follows:
_PC_LINK_MAX
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The maximum file link count.
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_PC_MAX_CANON
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The maximum number of bytes in terminal canonical input line.
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_PC_MAX_INPUT
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The minimum maximum number of bytes for which space is available in
a terminal input queue.
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_PC_NAME_MAX
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The maximum number of bytes in a file name.
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_PC_PATH_MAX
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The maximum number of bytes in a pathname.
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_PC_PIPE_BUF
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The maximum number of bytes which will be written atomically to a pipe.
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_PC_CHOWN_RESTRICTED
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Return 1 if appropriate privilege is required for the
chown(2)
system call, otherwise 0.
IEEE Std 1003.1-2001 ("POSIX.1")
requires appropriate privilege in all cases, but this behavior was optional
in prior editions of the standard.
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_PC_NO_TRUNC
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Return greater than zero if attempts to use pathname components longer than
{ NAME_MAX}
will result in an
[ENAMETOOLONG]
error; otherwise, such components will be truncated to
{ NAME_MAX}.
IEEE Std 1003.1-2001 ("POSIX.1")
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.
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_PC_VDISABLE
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Returns the terminal character disabling value.
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_PC_ASYNC_IO
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Return 1 if asynchronous I/O is supported, otherwise 0.
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_PC_PRIO_IO
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Returns 1 if prioritised I/O is supported for this file,
otherwise 0.
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_PC_SYNC_IO
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Returns 1 if synchronised I/O is supported for this file, otherwise 0.
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_PC_ALLOC_SIZE_MIN
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Minimum number of bytes of storage allocated for any portion of a file.
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_PC_FILESIZEBITS
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Number of bits needed to represent the maximum file size.
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_PC_REC_INCR_XFER_SIZE
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Recommended increment for file transfer sizes between
_PC_REC_MIN_XFER_SIZE
and
_PC_REC_MAX_XFER_SIZE.
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_PC_REC_MAX_XFER_SIZE
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Maximum recommended file transfer size.
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_PC_REC_MIN_XFER_SIZE
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Minimum recommended file transfer size.
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_PC_REC_XFER_ALIGN
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Recommended file transfer buffer alignment.
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_PC_SYMLINK_MAX
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Maximum number of bytes in a symbolic link.
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_PC_ACL_EXTENDED
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Returns 1 if an Access Control List (ACL) can be set on the specified
file, otherwise 0.
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_PC_ACL_NFS4
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Returns 1 if an NFSv4 ACLs can be set on the specified
file, otherwise 0.
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_PC_ACL_PATH_MAX
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Maximum number of ACL entries per file.
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_PC_CAP_PRESENT
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Returns 1 if a capability state can be set on the specified file,
otherwise 0.
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_PC_INF_PRESENT
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Returns 1 if an information label can be set on the specified file,
otherwise 0.
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_PC_MAC_PRESENT
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Returns 1 if a Mandatory Access Control (MAC) label can be set on the
specified file, otherwise 0.
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_PC_MIN_HOLE_SIZE
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If a file system supports the reporting of holes (see
lseek(2)),
pathconf()
and
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.
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