pathconf(3)

—

Options · 21

_PC_LINK_MAX	The maximum number of links to the file. If fd or path refer to a directory, then the value applies to the whole directory. The corresponding macro is _POSIX_LINK_MAX.
_PC_MAX_CANON	The maximum length of a formatted input line, where fd or path must refer to a terminal. The corresponding macro is _POSIX_MAX_CANON.
_PC_MAX_INPUT	The maximum length of an input line, where fd or path must refer to a terminal. The corresponding macro is _POSIX_MAX_INPUT.
_PC_NAME_MAX	The maximum length of a filename in the directory path or fd that the process is allowed to create. The corresponding macro is _POSIX_NAME_MAX.
_PC_PATH_MAX	The maximum length of a relative pathname when path or fd is the current working directory. The corresponding macro is _POSIX_PATH_MAX.
_PC_PIPE_BUF	The maximum number of bytes that can be written atomically to a pipe of FIFO. For fpathconf(), fd should refer to a pipe or FIFO. For fpathconf(), path should refer to a FIFO or a directory; in the latter case, the returned value corresponds to FIFOs created in that directory. The corresponding macro is _POSIX_PIPE_BUF.
_PC_CHOWN_RESTRICTED	This returns a positive value if the use of chown(2) and fchown(2) for changing a file's user ID is restricted to a process with appropriate privileges, and changing a file's group ID to a value other than the process's effective group ID or one of its supplementary group IDs is restricted to a process with appropriate privileges. According to POSIX.1, this variable shall always be defined with a value other than -1. The corresponding macro is _POSIX_CHOWN_RESTRICTED.
_PC_NO_TRUNC	This returns nonzero if accessing filenames longer than _POSIX_NAME_MAX generates an error. The corresponding macro is _POSIX_NO_TRUNC.
_PC_VDISABLE	This returns nonzero if special character processing can be disabled, where fd or path must refer to a terminal.
•	On error, -1 is returned and errno is set to indicate the error (for example, EINVAL, indicating that name is invalid).
•	If name corresponds to a maximum or minimum limit, and that limit is indeterminate, -1 is returned and errno is not changed. (To distinguish an indeterminate limit from an error, set errno to zero before the call, and then check whether errno is nonzero when -1 is returned.)
•	If name corresponds to an option, a positive value is returned if the option is supported, and -1 is returned if the option is not supported.
•	Otherwise, the current value of the option or limit is returned. This value will not be more restrictive than the corresponding value that was described to the application in <unistd.h> or <limits.h> when the application was compiled.
EACCES	(pathconf()) Search permission is denied for one of the directories in the path prefix of path.
EBADF	(fpathconf()) fd is not a valid file descriptor.
EINVAL	name is invalid.
EINVAL	The implementation does not support an association of name with the specified file.
ELOOP	(pathconf()) Too many symbolic links were encountered while resolving path.
ENAMETOOLONG	(pathconf()) path is too long.
ENOENT	(pathconf()) A component of path does not exist, or path is an empty string.
ENOTDIR	(pathconf()) A component used as a directory in path is not in fact a directory.

NAME

fpathconf, pathconf - get configuration values for files

SYNOPSIS

bash

#include <unistd.h>

bash

long fpathconf(int \nfd\n, int \nname\n);\n
\nlong pathconf(const char *\npath\n, int \nname\n);

DESCRIPTION

fpathconf() gets a value for the configuration option name for the open file descriptor fd.

pathconf() gets a value for configuration option name for the filename path.

The corresponding macros defined in <unistd.h> are minimum values; if an application wants to take advantage of values which may change, a call to fpathconf() or pathconf() can be made, which may yield more liberal results.

Setting name equal to one of the following constants returns the following configuration options:

_PC_LINK_MAX: The maximum number of links to the file. If fd or path refer to a directory, then the value applies to the whole directory. The corresponding macro is _POSIX_LINK_MAX.
_PC_MAX_CANON: The maximum length of a formatted input line, where fd or path must refer to a terminal. The corresponding macro is _POSIX_MAX_CANON.
_PC_MAX_INPUT: The maximum length of an input line, where fd or path must refer to a terminal. The corresponding macro is _POSIX_MAX_INPUT.
_PC_NAME_MAX: The maximum length of a filename in the directory path or fd that the process is allowed to create. The corresponding macro is _POSIX_NAME_MAX.
_PC_PATH_MAX: The maximum length of a relative pathname when path or fd is the current working directory. The corresponding macro is _POSIX_PATH_MAX.
_PC_PIPE_BUF: The maximum number of bytes that can be written atomically to a pipe of FIFO. For fpathconf(), fd should refer to a pipe or FIFO. For fpathconf(), path should refer to a FIFO or a directory; in the latter case, the returned value corresponds to FIFOs created in that directory. The corresponding macro is _POSIX_PIPE_BUF.
_PC_CHOWN_RESTRICTED: This returns a positive value if the use of chown(2) and fchown(2) for changing a file's user ID is restricted to a process with appropriate privileges, and changing a file's group ID to a value other than the process's effective group ID or one of its supplementary group IDs is restricted to a process with appropriate privileges. According to POSIX.1, this variable shall always be defined with a value other than -1. The corresponding macro is _POSIX_CHOWN_RESTRICTED.

: If fd or path refers to a directory, then the return value applies to all files in that directory.

_PC_NO_TRUNC: This returns nonzero if accessing filenames longer than _POSIX_NAME_MAX generates an error. The corresponding macro is _POSIX_NO_TRUNC.
_PC_VDISABLE: This returns nonzero if special character processing can be disabled, where fd or path must refer to a terminal.

RETURN VALUE

The return value of these functions is one of the following:

•: On error, -1 is returned and errno is set to indicate the error (for example, EINVAL, indicating that name is invalid).
•: If name corresponds to a maximum or minimum limit, and that limit is indeterminate, -1 is returned and errno is not changed. (To distinguish an indeterminate limit from an error, set errno to zero before the call, and then check whether errno is nonzero when -1 is returned.)
•: If name corresponds to an option, a positive value is returned if the option is supported, and -1 is returned if the option is not supported.
•: Otherwise, the current value of the option or limit is returned. This value will not be more restrictive than the corresponding value that was described to the application in <unistd.h> or <limits.h> when the application was compiled.

ERRORS

EACCES: (pathconf()) Search permission is denied for one of the directories in the path prefix of path.
EBADF: (fpathconf()) fd is not a valid file descriptor.
EINVAL: name is invalid.
EINVAL: The implementation does not support an association of name with the specified file.
ELOOP: (pathconf()) Too many symbolic links were encountered while resolving path.
ENAMETOOLONG: (pathconf()) path is too long.
ENOENT: (pathconf()) A component of path does not exist, or path is an empty string.
ENOTDIR: (pathconf()) A component used as a directory in path is not in fact a directory.