fpathconf, pathconf

#include <unistd.h>

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

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

returns 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

returns 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

returns 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

returns 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

returns 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

returns the size of the pipe buffer, where fd must refer to a pipe or FIFO and path must refer to a FIFO. The corresponding macro is _POSIX_PIPE_BUF.

_PC_CHOWN_RESTRICTED

returns nonzero if the chown(2) call may not be used on this file. If fd or path refer to a directory, then this applies to all files in that directory. The corresponding macro is _POSIX_CHOWN_RESTRICTED.

_PC_NO_TRUNC

returns nonzero if accessing filenames longer than _POSIX_NAME_MAX generates an error. The corresponding macro is _POSIX_NO_TRUNC.

_PC_VDISABLE

returns nonzero if special character processing can be disabled, where fd or path must refer to a terminal.

The limit is returned, if one exists. If the system does not have a limit for the requested resource, -1 is returned, and errno is unchanged. If there is an error, -1 is returned, and errno is set to reflect the nature of the error.

For an explanation of the terms used in this section, see attributes(7).

POSIX.1-2001, POSIX.1-2008.

Files with name lengths longer than the value returned for name equal to _PC_NAME_MAX may exist in the given directory.

Some returned values may be huge; they are not suitable for allocating memory.

getconf(1), open(2), statfs(2), confstr(3), sysconf(3)

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