Default returns the default file system.

New returns a standard file system.

a: append-only.

c: Unix character device, when ModeDevice is set.

D: device file.

d: is a directory.

l: exclusive use.

?: non-regular file; nothing else is known about this file.

p: named pipe (FIFO).

Unix permission bits, 0o777.

g: setgid.

u: setuid.

S: Unix domain socket.

t: sticky.

L: symbolic link.

T: temporary file; Plan 9 only.

Mask for the type bits.

append data to the file when writing.

create a new file if none exists.

used with O_CREATE, file must not exist.

open the file read-only.

open the file read-write.

open for synchronous I/O.

truncate regular writable file when opened.

open the file write-only.

File is an extended file interface for *os.File.

FileInfo describes a file and is returned by Stat and Lstat.

FileMode represents a file's mode and permission bits.