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man pages section 2: System Calls

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Updated: Thursday, June 13, 2019
 
 

fpathconf(2)

Name

fpathconf, pathconf - get configurable pathname variables

Synopsis

#include <unistd.h>

long fpathconf(int fildes, int name);
long pathconf(const char *path, int name);

Description

The fpathconf() and pathconf() functions determine the current value of a configurable limit or option ( variable ) that is associated with a file or directory.

For pathconf(), the path argument points to the pathname of a file or directory.

For fpathconf(), the fildes argument is an open file descriptor.

The name argument represents the variable to be queried relative to that file or directory. The variables in the following table come from <limits.h> or <unistd.h> and the symbolic constants, defined in <unistd.h >, are the corresponding values used for name:

Variable
Value of name
Notes
{ACL_ENABLED}
_PC_ACL_ENABLED
10
{FILESIZEBITS}
_PC_FILESIZEBITS
3,4
{LINK_MAX}
_PC_LINK_MAX
1
{MAX_CANON}
_PC_MAX_CANON
2
{MAX_INPUT}
_PC_MAX_INPUT
2
{MIN_HOLE_SIZE}
_PC_MIN_HOLE_SIZE
11
{NAME_MAX}
_PC_NAME_MAX
3, 4
{PATH_MAX}
_PC_PATH_MAX
4,5
{PIPE_BUF}
_PC_PIPE_BUF
6
{POSIX_ALLOC_SIZE_MIN}
_PC_ALLOC_SIZE_MIN
{POSIX_REC_INCR_XFER_SIZE}
_PC_REC_INCR_XFER_SIZE
{POSIX_REC_MAX_XFER_SIZE}
_PC_REC_MAX_XFER_SIZE
{POSIX_REC_MIN_XFER_SIZE}
_PC_REC_MIN_XFER_SIZE
{POSIX_REC_XFER_ALIGN}
_PC_REC_XFER_ALIGN
{REFLINK_ENABLED}
_PC_REFLINK_ENABLED
{SYMLINK_MAX}
_PC_SYMLINK_MAX
4, 9
{XATTR_ENABLED}
_PC_XATTR_ENABLED
1
{SATTR_ENABLED}
_PC_SATTR_ENABLED
{XATTR_EXISTS}
_PC_XATTR_EXISTS
1
{SATTR_EXISTS}
_PC_SATTR_EXISTS
{ACCESS_FILTERING}
_PC_ACCESS_FILTERING
12
_POSIX_CHOWN_RESTRICTED
_PC_CHOWN_RESTRICTED
7
_POSIX_NO_TRUNC
_PC_NO_TRUNC
3, 4
_POSIX_VDISABLE
_PC_VDISABLE
2
_POSIX_ASYNC_IO
_PC_ASYNC_IO
8
_POSIX_PRIO_IO
_PC_PRIO_IO
8
_POSIX_SYNC_IO
_PC_SYNC_IO
8
_POSIX_TIMESTAMP_RESOLUTION
_PC_TIMESTAMP_RESOLUTION
1

Notes:

  1. If path or fildes refers to a directory, the value returned applies to the directory itself.

  2. If path or fildes does not refer to a terminal file, it is unspecified whether an implementation supports an association of the variable name with the specified file.

  3. If path or fildes refers to a directory, the value returned applies to filenames within the directory.

  4. If path or fildes does not refer to a directory, it is unspecified whether an implementation supports an association of the variable name with the specified file.

  5. 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 working directory.

  6. If path refers to a FIFO, or fildes refers to a pipe or FIFO, the value returned applies to the referenced object. If path or fildes refers to a directory, the value returned applies to any FIFO that exists or can be created within the directory. If path or fildes refers to any other type of file, it is unspecified whether an implementation supports an association of the variable name with the specified file.

  7. If path or fildes refers to a directory, the value returned applies to any files, other than directories, that exist or can be created within the directory.

  8. If path or fildes refers to a directory, it is unspecified whether an implementation supports an association of the variable name with the specified file.

  9. If path or fildes refers to a directory, the value returned is the maximum length of the string that a symbolic link in that directory can contain.

  10. If path or fildes refers to a file or directory in a file system that supports ACLs, the value returned is the bitwise inclusive OR of the following flags associated with ACL types supported by the file system; otherwise 0 is returned.

    _ACL_ACE_ENABLED

    The file system supports ACE ACLs.

    _ACL_ACLENT_ENABLED

    The file system supports UFS aclent ACLs.

  11. If a filesystem 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 filesystem does not specify the minimum hole size but still reports holes.

  12. If path or fildes refers to a directory and the file system in which the directory resides supports access filtering, a non-zero value is returned. Otherwise, 0 is returned.

Return Values

If name is an invalid value, both pathconf() and fpathconf() return −1 and errno is set to indicate the error.

If the variable corresponding to name has no limit for the path or file descriptor, both pathconf() and fpathconf() return −1 without changing errno. If pathconf () needs to use path to determine the value of name and pathconf() does not support the association of name with the file specified by path, or if the process did not have appropriate privileges to query the file specified by path, or path does not exist, pathconf() returns −1 and errno is set to indicate the error.

If fpathconf() needs to use fildes to determine the value of name and fpathconf() does not support the association of name with the file specified by fildes, or if fildes is an invalid file descriptor, fpathconf() returns −1 and errno is set to indicate the error.

Otherwise pathconf() or fpathconf() returns the current variable value for the file or directory without changing errno. The value returned will not be more restrictive than the corresponding value available to the application when it was compiled with <limits.h> or <unistd.h>.

Errors

The pathconf() function will fail if:

EINVAL

The value of name is not valid.

ELOOP

A loop exists in symbolic links encountered during resolution of the path argument.

The fpathconf() function will fail if:

EINVAL

The value of name is not valid.

The pathconf() function may fail if:

EACCES

Search permission is denied for a component of the path prefix.

EINVAL

An association of the variable name with the specified file is not supported.

ENAMETOOLONG

The length of the path argument exceeds {PATH_MAX} or a pathname component is longer than {NAME_MAX}.

ENAMETOOLONG

As a result of encountering a symbolic link in resolution of the path argument, the length of the substituted pathname string exceeded {PATH_MAX}.

ENOENT

A component of path does not name an existing file or path is an empty string.

ENOTDIR

A component of the path prefix is not a directory.

The fpathconf() function may fail if:

EBADF

The fildes argument is not a valid file descriptor.

EINVAL

An association of the variable name with the specified file is not supported.

Usage

The {SYMLINK_MAX} variable applies only to the fpathconf() function.

Attributes

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Interface Stability
Committed
MT-Level
Async-Signal-Safe
Standard

See Also

lseek(2), confstr(3C), sysconf(3C), limits.h(3HEAD), attributes(7), standards(7)