A File is an abstraction of any file object accessible by the program and is closely associated with class IO. File includes the methods of module FileTest as class methods, allowing you to write (for example) File.exist?("foo").
In this section, permission bits are a platform-specific set of bits that indicate permissions of a file. On Unix-based systems, permissions are viewed as a set of three octets, for the owner, the group, and the rest of the world. For each of these entities, permissions may be set to read, write, or execute (or search, if a directory) the file:
| Owner | Group | Other | ||||||
|---|---|---|---|---|---|---|---|---|
| r | w | x | r | w | x | r | w | x |
| 4 | 2 | 1 | 4 | 2 | 1 | 4 | 2 | 1 |
The permission bits 0644 (in octal) would thus be interpreted as read/write for owner, and read-only for group and other. Higher-order bits may also be used to indicate the type of file (plain, directory, pipe, socket, and so on) and various other special features.
On non-Posix operating systems, there may be only the ability to make a file read-only or not. In this case, the remaining permission bits will be synthesized to resemble typical values. For instance, on Windows NT the default permission bits are 0644, which means read/write for owner, read-only for all others. The only change that can be made is to make the file read-only, which is reported as 0444.
FileTestblockdev?, chardev?, directory?, executable?, executable_real?, exist?, exists?, file?, grpowned?, owned?, pipe?, readable?, readable_real?, setgid?, setuid?, size, size?, socket?, sticky?, symlink?, writable?, writable_real?, zero?File.atime("testfile") → Sun Jun 09 00:09:52 CDT 2002/”) regardless of the separator used on the local file system. If aSuffix is given and present at the end of fileName, it is removed.
File.basename("/home/gumby/work/ruby.rb") → "ruby.rb"
File.basename("/home/gumby/work/ruby.rb", ".rb") → "ruby"chmod(2) for details. Returns the number of files processed.
File.chmod(0644, "testfile", "out") → 2Changes the owner and group of the named file(s) to the given numeric owner and group id's. Only a process with superuser privileges may change the owner of a file. The current owner of a file may change the file's group to any group to which the owner belongs. A nil or -1 owner or group id is ignored.
Returns the number of files processed.
File.chown(nil, 100, "testfile")File.ctime("testfile") → Sun Jun 09 00:17:17 CDT 2002Deletes the named file(s). Returns the number of files processed.
See also Dir.rmdir.
File.new("testrm", "w+").close → nil
File.delete("testrm") → 1/”) regardless of the separator used on the local file system.
File.dirname("/home/gumby/work/ruby.rb") → "/home/gumby/work"~”, which expands to the process owner's home directory (the environment variable HOME must be set correctly). “~user” expands to the named user's home directory.
File.expand_path("~oracle/bin") → "/home/oracle/bin"
File.expand_path("../../bin", "/tmp/x") → "/bin"file”, “directory”, “characterSpecial”, “blockSpecial”, “fifo”, “link”, or “socket”.
File.ftype("testfile") → "file"
File.ftype("/dev/tty") → "characterSpecial"
File.ftype("/tmp/.X11-unix/X0") → "socket"Returns a new string formed by joining the strings using File::SEPARATOR (see Table 22.2).
File.join("usr", "mail", "gumby") → "usr/mail/gumby"ALT_SEPARATOR |
Alternate path separator. |
PATH_SEPARATOR |
Character that separates filenames in a search path (such as “:” or “;”). |
SEPARATOR |
Character that separates directory components in a filename (such as “\” or “/”). |
Separator |
Alias for SEPARATOR. |
SystemCallError). Not available on all platforms.
File.link("testfile", ".testfile") → 0
IO.readlines(".testfile")[0] → "This is line one\n"IO#stat, but does not follow the last symbolic link.
Instead, reports on the link itself.
File.symlink("testfile", "link2test") → 0
File.stat("testfile").size → 66
File.lstat("link2test").size → 8
File.stat("link2test").size → 66File.mtime("testfile") → Sun Nov 25 23:48:26 CST 2001File object. See Table 22.5 for a description of aModeString. The file mode may optionally be specified as a Fixnum by or-ing together the flags described in Table 22.3. Optional permission bits may be given in aPermNum. These mode and permission bits are platform dependent; on Unix systems, see open(2) for details.
f = File.new("testfile", "r")
f = File.new("newfile", "w+")
f = File.new("newfile", File::CREAT|File::TRUNC|File::RDWR, 0644)APPEND |
Open the file in append mode; all writes will occur at end of file. |
CREAT |
Create the file on open if it does not exist. |
EXCL |
When used with CREAT, open will fail if the file exists. |
NOCTTY |
When opening a terminal device (see IO#isatty), do not allow it to become the controlling terminal. |
NONBLOCK |
Open the file in nonblocking mode. |
RDONLY |
Open for reading only. |
RDWR |
Open for reading and writing. |
TRUNC |
Open the file and truncate it to zero length if the file exists. |
WRONLY |
Open for writing only. |
nilnilopen is a synonym for File.new. If the optional code block is given, it will be passed file as an argument, and the file will automatically be closed when the block terminates. In this instance, File.open returns nil. File.symlink("testfile", "link2test") → 0
File.readlink("link2test") → "testfile"SystemCallError if the file cannot be renamed.
File.rename("afile", "afile.bak") → 0File.size("testfile") → 66File.dirname and File.basename.
File.split("/home/gumby/.profile") → ["/home/gumby", ".profile"]File::Stat object for the named file (see File::Stat).
File.stat("testfile").mtime → Sun Nov 25 23:48:26 CST 2001nilnil on all platforms that do not support symbolic links.
File.symlink("testfile", "link2test") → 0f = File.new("out", "w")
f.write("1234567890") → 10
f.close → nil
File.truncate("out", 5) → 0
File.size("out") → 50222 would make a file read-only for everyone. See also the discussion of permissions.
File.umask(0006) → 18
File.umask → 6File.delete. See also Dir.rmdir. Time or integers representing the number of seconds since epoch. Returns the number of files processed. Not available on all platforms.
File.utime(0, 0, "testfile") → 1
File.mtime("testfile") → Wed Dec 31 18:00:00 CST 1969
File.utime(0, Time.now, "testfile") → 1
File.mtime("testfile") → Sun Jun 09 00:17:19 CDT 2002File.new("testfile").atime → Wed Dec 31 18:00:00 CST 19690chmod(2) for details. See the discussion of permissions.
f = File.new("out", "w");
f.chmod(0644) → 0nil or -1 owner or group id is ignored.
File.new("testfile").chown(502, 1000)File.new("testfile").ctime → Sun Jun 09 00:17:19 CDT 2002falsefalse if File::LOCK_NB is specified and the operation would otherwise have blocked. Not available on all platforms.
File.new("testfile").flock(File::LOCK_UN) → 0LOCK_EX |
Exclusive lock. Only one process may hold an exclusive lock for a given file at a time. |
LOCK_NB |
Don't block when locking. May be combined with other lock options using logical or. |
LOCK_SH |
Shared lock. Multiple processes may each hold a shared lock for a given file at the same time. |
LOCK_UN |
Unlock. |
IO#stat, but does not follow the last symbolic link.
Instead, reports on the link itself.
File.symlink("testfile", "link2test") → 0
File.stat("testfile").size → 66
f = File.new("link2test")
f.lstat.size → 8
f.stat.size → 66File.new("testfile").mtime → Sun Jun 09 00:17:19 CDT 2002File.new("testfile").path → "testfile"f = File.new("out", "w")
f.syswrite("1234567890") → 10
f.truncate(5) → 0
f.close() → nil
File.size("out") → 5Extracted from the book "Programming Ruby - The Pragmatic Programmer's Guide"
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