pathconf

Retrieves file implementation characteristics.

Format

#include  <unistd.h>

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

Arguments

path: The pathname of a file or directory.
name: The configuration attribute to query. If this attribute is not applicable to the file specified by the path argument, the pathconf function returns an error.

Description

This function allows an application to determine the characteristics of operations supported by the file system underlying the file named by path. Read, write, or execute permission of the named file is not required, but you must be able to search all directories in the path leading to the file.

Symbolic values for the name argument are defined in the <unistd.h> header file, as follows:

_PC_LINK_MAX The maximum number of links to the file. If the path argument refers to a directory, the value returned applies to the directory itself.

_PC_MAX_CANON The maximum number of bytes in a canonical input line. This is applicable only to terminal devices.

_PC_MAX_INPUT The number of types allowed in an input queue. This is applicable only to terminal devices.

_PC_NAME_MAX Maximum number of bytes in a filename (not including a terminating null). The byte range value is between 13 and 255. This is applicable only to a directory file. The value returned applies to filenames within the directory.

_PC_PATH_MAX Maximum number of bytes in a pathname (not including a terminating null). The byte value is never larger than 65,535. This is applicable only to a directory file. The value returned is the maximum length of a relative pathname when the specified directory is the working directory.

_PC_PIPE_BUF Maximum number of bytes guaranteed to be written atomically. This is applicable only to a FIFO. The value returned applies to the referenced object. If the path argument refers to a directory, the value returned applies to any FIFO that exists or can be created within the directory.

_PC_CHOWN_RESTRICTED This is applicable only to a directory file. The value returned applies to any files (other than directories) that exist or can be created within the directory.

_PC_NO_TRUNC Returns 1 if supplying a component name longer than allowed by NAME_MAX causes an error. Returns 0 (zero) if long component names are truncated. This is applicable only to a directory file.

_PC_VDISABLE This is always 0 (zero); no disabling character is defined. This is applicable only to a terminal device.

Return Values

x Resultant value of the configuration attribute specified in name.

- 1 Indicates an error; errno is set to one of the following values:

EACCES - Search permission is denied for a component of the path prefix.
EINVAL - The name argument specifies an unknown or inapplicable characteristic.
EFAULT - The path argument is an invalid address.
ENAMETOOLONG - The length of the path string exceeds PATH_MAX or a pathname component is longer than NAME_MAX.
ENOENT - The named file does not exist or the path argument points to an empty string.
ENOTDI - A component of the path prefix is not a directory.

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_PC_LINK_MAX	The maximum number of links to the file. If the path argument refers to a directory, the value returned applies to the directory itself.
_PC_MAX_CANON	The maximum number of bytes in a canonical input line. This is applicable only to terminal devices.
_PC_MAX_INPUT	The number of types allowed in an input queue. This is applicable only to terminal devices.
_PC_NAME_MAX	Maximum number of bytes in a filename (not including a terminating null). The byte range value is between 13 and 255. This is applicable only to a directory file. The value returned applies to filenames within the directory.
_PC_PATH_MAX	Maximum number of bytes in a pathname (not including a terminating null). The byte value is never larger than 65,535. This is applicable only to a directory file. The value returned is the maximum length of a relative pathname when the specified directory is the working directory.
_PC_PIPE_BUF	Maximum number of bytes guaranteed to be written atomically. This is applicable only to a FIFO. The value returned applies to the referenced object. If the path argument refers to a directory, the value returned applies to any FIFO that exists or can be created within the directory.
_PC_CHOWN_RESTRICTED	This is applicable only to a directory file. The value returned applies to any files (other than directories) that exist or can be created within the directory.
_PC_NO_TRUNC	Returns 1 if supplying a component name longer than allowed by NAME_MAX causes an error. Returns 0 (zero) if long component names are truncated. This is applicable only to a directory file.
_PC_VDISABLE	This is always 0 (zero); no disabling character is defined. This is applicable only to a terminal device.