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DRAFT: Synopsis 32: Setting Library - IO


    The authors of the related Perl 5 docs
    Rod Adams <>
    Larry Wall <>
    Aaron Sherman <>
    Mark Stosberg <>
    Carl Mäsak <>
    Moritz Lenz <>
    Tim Nelson <>
    Daniel Ruoso <>
    Lyle Hopkins <>


    Created: 19 Feb 2009 extracted from S29-functions.pod; added stuff from S16-IO later

    Last Modified: 4 July 2010
    Version: 13

The document is a draft.

If you read the HTML version, it is generated from the Pod in the specs repository under so edit it there in the git repository if you would like to make changes.


[Note: if a method declaration indicates a method name qualified by type, it should be taken as shorthand to say which role or class the method is actually declared in.]

    multi open (Str $name,
        Bool :$rw = False,
        Bool :$bin = False,
        Str  :$enc = "Unicode",
        Any  :$nl = "\n",
        Bool :$chomp = True,
        --> IO
    ) is export

A convenience method/function that hides most of the OO complexity. It will only open normal files. Text is the default. Note that the "Unicode" encoding implies figuring out which actual UTF is in use, either from a BOM or other heuristics. If heuristics are inconclusive, UTF-8 will be assumed. (No 8-bit encoding will ever be picked implicitly.) A file opened with :bin may still be processed line-by-line, but IO will be in terms of Buf rather than Str types.

TODO: document read/write/append modes (:r, :w, :a)

    multi dir($directory = '.', Mu :$test = none('.', '..')) { ... }

Returns a lazy list of file names in the $directory. By default the current and the parent directory are excluded, which can be controlled with the $test named paramater. Only items that smart-match against this test are returned.

    method getc (Int $chars = 1 --> Char)

See below for details.

    method print (*@LIST --> Bool)
    multi print (*@LIST --> Bool)
    method Str::print (IO $io --> Bool)
    method Array::print (IO $io --> Bool)
    method Hash::print (IO $io --> Bool)

See below for details.

    method say (*@LIST --> Bool)
    multi say (*@LIST --> Bool)
    method Str::say (IO $io --> Bool)
    method Array::say (IO $io --> Bool)
    method Hash::say (IO $io --> Bool)

See below for details.

    multi note (*@LIST --> Bool)

See below for details.

    method printf (Str $fmt, *@LIST --> Bool)
    multi printf (Str $fmt, *@LIST --> Bool)

See below for details.

    method uri(Str $uri --> IO::Streamable);
    sub uri(Str $uri --> IO::Streamable);

Returns an appropriate IO::Streamable descendant, with the type depending on the uri passed in. Here are some example mappings:

    URI type IO type
    ======== =======
    file:    IO::File or IO::Directory
    ftp:     IO::Socket::INET (data channel)
    http:    IO::Socket::INET

These can naturally be overridden or added to by other modules.

%*PROTOCOLS dynamic variable

For each protocol, stores a type name that should be instantiated by calling the uri constructor on that type, and passing in the appropriate uri.


The functionality of IO objects is broken down into several roles, which should identify the features each object supports.


The base role only tags that this is an IO object for more generic purposes. It doesn't specify any methods or attributes.


This role provides unbuffered read access to the data stream.

    role IO::Readable {
        has $.isReadable;
        method read(Int $bytes --> Buf)

When the $.isReadable is set, it tries to change the readability of the filehandle. This is not always possible, but can be done in a number of cases. IO::Socket can remove readability by calling shutdown, for example.

method read(Int $bytes --> Buf)

Tries to read $bytes bytes and return it as a Buf. The Buf may be shorter than the actual specified number of $bytes.

This is "raw" read. You're going to have plain octets stored in $buf. If what you want is a Str, you're going to need to .decode it after reading, or use "getc" or other IO::Readable::Encoded methods.


This role provides unbuffered write access to the data stream.

    role IO::Writeable {
        has $.isWriteable;
        method write(Buf $buf --> Int)

When the $.isWriteable is set, it tries to change the writeability of the filehandle. This is not always possible, but can be done in a number of cases. IO::Socket can remove writeability by calling shutdown(), for example.

method write(Buf $buf --> Int)

Tries to write $buf. The actual number of bytes written is returned. It might return unthrown failures, to be specified by each IO implementation.

This is "raw" write. $buf contains plain octets. If you want to write a Str, you should .encode it first, or use "print" or other IO::Writeable::Encoded methods.


method eoi( --> Bool)

EOI = End Of Input -- equivalent to End Of File, but applies to other kinds of sockets as well.

Returns true if it's the end of the input (i.e. end of file or whatever), returns false if not, fails if we can't say for certain.

method seek(Int $position --> Bool)

Position this stream into $position. The meaning of this position is always in "octets".

method tell( --> Int)

Returns the current raw position in the stream in number of "octets".


Indicates that this object performs buffering. The management of the buffer is completely implementation specific.

method flush( --> Bool)

Flushes the buffers associated with this object.

method autoflush( --> Bool) is rw

Forces this object to keep its buffers empty

If set to nonzero, forces a flush right away and after every write or print on the currently selected output channel. Default is 0 (regardless of whether the channel is really buffered by the system or not; $OUT_FH.autoflush tells you only whether you've asked Perl explicitly to flush after each write). $*OUT will typically be line buffered if output is to the terminal and block buffered otherwise. Setting this variable is useful primarily when you are outputting to a pipe or socket, such as when you are running a Perl program under rsh and want to see the output as it's happening. This has no effect on input buffering.


This role represents objects that depend on some external resource, which means that data might not be available at request.

    role IO::Streamable does IO {...}
    method new(
        Bool :$NoOpen,
        Bool :$Blocking,
        --> IO::Streamable
    ) {...}

Unless the NoOpen option is passed, an open will be done on the IO object when it is created.

If blocking is passed in, .blocking() is called (see below).

method blocking( --> Bool) is rw

This allows the user to control whether this object should do a blocking wait or immediately return in the case of not having data available.

    method uri(Str $uri --> IO::Streamable) {...}

This should be callable on the class, and act like a kind of "new()" function. When given a URI, it returns an IO::Streamable of the appropriate type, and throws an error when an inappropriate type is passed in. For example, calling IO::File.uri('http://....') will throw an error (but will suggest using just uri('http://...') instead).


This is a generic role for encoded data streams.

method encoding( --> Str) is rw
method locale( --> Str) is rw

Encoding and locale are required for sane conversions.


This role provides encoded access to a readable data stream, implies IO::Encoded. Might imply IO::Buffered, but that's not a requirement.

method ins( --> Int)

Returns the number of lines or records that have been input. Now with cleaned-up localization usage.

method input-line-separator( --> Str) is rw

This regulates how "get" and "lines" behave.

The input line (record) separator, newline by default. This influences Perl's idea of what a ``line'' is. Works like awk's RS variable, including treating empty lines as a terminator if set to the null string. (An empty line cannot contain any spaces or tabs.) You may set it to a multi-character string to match a multi-character terminator, or to Nil to read through the end of file. Setting it to "\n\n" means something slightly different than setting to "", if the file contains consecutive empty lines. Setting to "" will treat two or more consecutive empty lines as a single empty line. Setting to "\n\n" will blindly assume that the next input character belongs to the next paragraph, even if it's a newline.

You may also set it to a regular expression. The value of $/ will be (temporarily) set to the matched separator upon input, if you care about the contents of the separator.

method input-field-separator( --> Str) is rw


method input-escape( --> Str) is rw


method get( --> Str)

Reads the stream before it finds a $.input-line-separator and returns it (autochomped by default).

method readfield( --> Str)

[Deprecated. Use split or comb or an ILS regex.]

method getc( --> Char)

Reads the next character in the set $.encoding, or Failure at end of file, or if there was an error (in either case $! is set). Note that this function cannot be used interactively as a readkey() function, since under Unicode you can't tell the end of a grapheme until you see the beginning of the next one.

[TODO someone needs to define something like readkey() for terminal IO. Though most event-based programs will just want to feed keystrokes into the event queue.]

multi method comb ( Regex $matcher, Int $limit = * )

Reads everything into a string, and calls .comb on it with the same parameters. See Str::comb.


This role provides encoded access to a writeable data stream, implies IO::Encoded. Might imply IO::Buffered, but that's not a requirement.

If these are called in their non-object form, they operate on $*OUT, except in the case of warn(), which operates on $*ERR. The form with leading dot prints $_ to the appropriate handle unless $_ happens to be a filehandle.

Int method outs()

Returns the number of lines or records that have been output so far.

method output-line-separator( --> Str) is rw

This regulates how say behaves.

method output-field-separator( --> Str) is rw


method output-escape( --> Str) is rw


method Str::print (IO $io = $*OUT --> Bool)
method Str::say (IO $io = $*OUT --> Bool)
method Array::print(IO $io = $*OUT --> Bool)
method Array::say(IO $io = $*OUT --> Bool)
method Hash::print(IO $io = $*OUT --> Bool)
method Hash::say(IO $io = $*OUT --> Bool)

Stringifies the invocant (if necessary) and then sends it to the output. say should add an additional $.output-line-separator.

method print (*@LIST --> Bool)
multi print (*@LIST --> Bool)

Stringifies each element, concatenates those strings, and sends the result to the output. Returns Bool::True if successful, Failure otherwise.

The compiler will warn you if use a bare print without arguments. (However, it's fine if you have an explicit argument list that evaluates to the empty list at runtime.)

    print;             # warns
    if $_ { print }    # warns
    if $_ { print() }  # ok, but does nothing
    if $_ { print () } # ok, but does nothing
method say (*@LIST --> Bool)
multi say (*@LIST --> Bool)

This is identical to print() except that it auto-appends the output-line-separator after the final argument.

    Was:    print "Hello, world!\n";
    Now:    say   "Hello, world!";

As with print, the compiler will warn you if you use a bare say without arguments.

multi note (*@LIST --> Bool)

Does a "say" to $*ERR, more or less. Like warn, it adds a newline only if the message does not already end in newline. Unlike warn, it is not trappable as a resumable exception because it outputs directly to $*ERR. You can suppress notes in a lexical scope by declaring:

    only note(*@) {}
method printf ($self: Str $fmt, *@LIST --> Bool)
multi printf (Str $fmt, *@LIST --> Bool)

The function form works as in Perl 5 and always prints to $*OUT.

For any handle marked as textual, all these output calls intercept any newline character and translate it to the current output-line-separator if it is defined as something other than newline. No such translation is done on binary handles, though you may still specify a record separator. In any case, escaping separators is the responsibility of the programmer.


This role indicates that this object can be closed.

method close( --> Bool)

Closes the file or pipe associated with the object.

Returns True on success, but might return an unthrown Failure. Returns true only if IO buffers are successfully flushed and closes the system file descriptor.

Unlike in Perl 5, an IO object is not a special symbol table entry neither this object is available magically anywhere else. But as in Perl 5, unless stated otherwise, IO::Closeable objects always close themselves during destruction.


    role IO::Socket
        does IO::Closeable
        does IO::Readable
        does IO::Writeable
        does IO::Streamable
        has %.options;
        has Bool $.Listener;

Accessing the %.options would on Unix be done with getsockopt(2)/setsockopt(2).

The $.Listener attribute indicates whether the socket will be a listening socket when opened, rather than indicating whether it is currently listening.

    method new(
        :$Listener, # initialises $.Listener

The initial value of the $.Listener attribute is defined according to the following rules:

 * If $Listener is passed to .new(), then that value is used
 * If neither a local address nor a remote address are passed in, throw an exception
 * If no remote address is passed, then $.Listener is set to SOMAXCONN
 * If no local address is used, then $Listener is set to 0
 * If both local and remote addresses are used, throw an exception that asks people to
   specify $Listener
    method open()

If $.Listener is true, does a bind(2) and a listen(2), otherwise does a connect(2).

It's end-user use case is intended for the case where NoOpen is passed to .new(). .new() itself will presumably also call it.

    method close()

Implements the close() function from IO::Closeable by doing a shutdown on the connection (see below) with @how set to ('Readable', 'Writeable').

    method shutdown(Str @how)

Does a shutdown(2) on the connection. See also IO::Readable.isReadable and IO::Writeable.isWriteable.

$how can contain 1 or more of the strings 'Readable' and 'Writeable'.

    method accept( --> IO::Socket)
method read($buf is rw, Int $bytes --> Int)

Implements the IO::Readable interface by doing a recv(2).

method write($buf, Int $bytes --> Int)

Implements the IO::Writeable interface by doing a send(2).



This role indicates that this object actually represents an open file descriptor in the os level.

method int fileno()

File descriptors are always native integers, conforming to C89.



This does file input and output.

    class IO::File does IO::Streamable {
    method new(
        Path :$Path,
        Bool :$NoOpen,

The Path and fd options are mutually exclusive.

NoOpen is passed to


    # Read, no interpolation
    $fobj = => qp{/path/to/file});

    # Write, interpolation
    $fobj =
        Path => p:qq{$filename},
        Writeable => 1

    # Read using file descriptor
    $fobj = => $fd);

This final example associates an IO object with an already-open file descriptor, presumably passed in from the parent process.


This function opens a file that had the NoOpen option passed to the new method.


Available only as a handle method.


    role IO::Directory does IO::Streamable {
        Str  :$enc = "Unicode",

Opens a directory for processing, if the new method was passed the NoOpen option. Makes the directory looks like a list of autochomped lines, so just use ordinary IO operators after the open.


This represents the file systems mounted on the current machine (i.e. accessible via a filesystem path).

    class IO::FileSystems {
        has Str $.illegal-chars; # i.e. /\x0
        has Int $.max-path;
        has Int $.max-path-element;

Changes the current working directory to the one specified by FILENAME. If it succeeds it returns true, otherwise it returns Failure and sets $! (errno). Note, though, that chdir affects only the system directory; most things in Perl 6 that need a current directory depend on their thread's copy of $*CWD, so you probably want to set $*CWD instead of using chdir().


Returns Path objects. Path.Encoding is set to $?ENC unless the $Encoding parameter is passed in (see Path for further discussion of encoding).


Returns Path objects. Path.Encoding is set to $?ENC unless the Encoding parameter is passed in (see Path for further discussion of encoding).



The "Path" role covers both the path to the file, and the file metadata. They are usually created with the qp{/path/to/file} syntax. It could be a directory, file, link, or something else OS-specific.

    role Path does Str does Array {
        has Str $.Type;
        has Str @.Elements;
        has Str $.Encoding;
        has Buf $.Binary;
        has IO::ACL @.ACLs;
        has %.times;

$.Type can be File, Directory, Link, or Other. See .create() method documentation for how it is set.

The @.Elements array is a list of Str that contain the path elements, but all are checked before being pushed onto the array. Note that @.Elements can not be accessed unless $.Encoding is defined.

The %.times has keys that can be e.g. ctime, Modification, and Access (and maybe others on other operating systems), and the values are all Instant objects.

When a Path is used as a Str, it allows some operations, so that it can be concatenated easily with other strings. When used as an Array, it acts as an array of path elements.



While new Path objects will normally be created with the qp{/path/to/file} syntax, there are also OO-related alternatives.

This is called automatically on object creation.

    multi method new(
        Stringy :$Path,
        Str :@PathElements,
        Str :$Encoding,

        Str :@Constraints, 
        Str :$Protocol,

        Str :$Target,
        Str :$LinkType,
        Str :$Type,

Path and PathElements are mutually exclusive.

If the $Encoding parameter is not defined, then, if Path is a Buf, the $.Encoding attribute remains undefined, otherwise it is set to $?ENC. There are a number of features that don't work without the encoding being set.

$Constraints determines whether the $Path and $Target strings should be assumed to be Unix-style, Windows-style, or something else.

If the Type option is not passed in, the Path.Type attribute is initialised as follows:

    Value        Condition
    =====        =========
    Directory    $Path ends in a separator (i.e. /)
    Link         $Target is specified
    Other        $Protocol is specified
    Undefined    All other cases

If the $.Type attribute is read (which will happen in a number of cases, including when you read $.Target and $.LinkType), but is still undefined, then an attempt is made to determine what its type should be from the filesystem. If no answers are found using this method, then it defaults to "File".

The Target and LinkType options are only relevant for links that have not been created yet, or are to be overwritten; in all other cases, they will be determined from the filesystem. If Target is not specified, this Path is assumed not to be a link. If LinkType is not specified, then the default is used (symbolic, on a Unix system).


    # These three do the same thing (on a Unix machine)
    $path = qp{/home/wayland};
    $path = => ['home', 'wayland']);
    $path = => ['Unix'], Path => qp{/home/wayland});
    $path = => qp{/home/wayland});

    # This creates a symlink from /home/wayland/m to /home/wayland/Music
    $path =
        Path => qp{/home/wayland/m},
        Target => qp{/home/wayland/Music},

method path( --> Str);

Returns @.elements concatenated together for use as a string. Usually this is the path that it was originally created with.

    method canonpath( --> Str);

No physical check on the filesystem, but a logical cleanup of a path.

    method realpath( --> Str);

Gets the real path to the object, resolving softlinks/shortcuts, etc

    method resolvepath(Str :@Types --> Str);

@Types can contain "real" and "canon", in any order, and the method will run realpath and canonpath in the order specified.

    multi method ACCEPTS(Path $filename);

Test whether the specified filename is the same file as this file. On a Unix system, this would presumably be done by comparing inode numbers or something.

    method create(
        Bool :$Recursive,
        Bool :$Truncate,

Creates/touches the specified path. In the case of a link or a directory, no parameters are required. If a file doesn't exist, then no parameters are required. If the path already exists, then an exception is thrown, unless the file is an ordinary file or a link, and $Truncate is true.

The $Recursive option specifies that any necessary parent directories should also be created.


Update timestamps on a file.


    method delete(Bool :$Recursive --> Int);

This deletes the Path from the filesystem. If the node has children, it throws an error unless the Recursive option is specified. It returns the number of nodes deleted, and may throw an exception.

    multi get () 

Returns the next line from $*ARGFILES. (Note that other get functions and methods are operations on any iterator, not just an IO handle.)

    method lines ($handle:
        Any  $limit = *,
        Bool :$bin = False,
        Str  :$enc = "Unicode",
        Any  :$nl = "\n",
        Bool :$chomp = True,
        --> List

    multi lines (IO $fh = $*ARGFILES,
        Any  $limit = *,
        Bool :$bin = False,
        Str  :$enc = "Unicode",
        Any  :$nl = "\n",
        Bool :$chomp = True,
        --> List

    # See also Str.lines and lines(Str)

Returns some or all the lines of a file or entries in a directory as a List regardless of context. See also slurp. Note that lists are lazy by default, but you can always ask for eager lines. Note that the limit semantics cannot be duplicated by subscripting, since


reads all the lines before the subscript gives you the first five, whereas


reads only five lines from the handle. Note that


is equivalent to


If fewer lines are available than the limit, it is not an error; you just get the number of lines available.

    method slurp ($handle:
        Bool :$bin = False,
        Str  :$enc = "Unicode",
        --> Str|Buf
    multi slurp (IO $fh = $*ARGFILES,
        Bool :$bin = False,
        Str  :$enc = "Unicode",
        --> Str|Buf
    multi slurp (Str $filename,
        Bool :$bin = False,
        Str  :$enc = "Unicode",
        --> Str|Buf

Slurps the entire file into a Str (or Buf if :bin) regardless of context. (See also lines.)

In the case of a directory, it uses "\n" to separate entries.

Other things

IO ~~ :X
EXPR ~~ :X
  $file ~~ :X

A file test, where X is one of the letters listed below. This unary operator takes one argument, either a filename or a filehandle, and tests the associated file to see if something is true about it.

A Pair used as a pattern is treated as a file test.

    :r  File is readable by effective uid/gid.
    :w  File is writable by effective uid/gid.
    :x  File is executable by effective uid/gid.
    :o  File is owned by effective uid.

    :R  File is readable by real uid/gid.
    :W  File is writable by real uid/gid.
    :X  File is executable by real uid/gid.
    :O  File is owned by real uid.

    :e  File exists.
    :s  File has a size > 0 bytes

    :f  File is a plain file.
    :d  File is a directory.
    :l  File is a symbolic link.
    :p  File is a named pipe (FIFO), or Filehandle is a pipe.
    :S  File is a socket.
    :b  File is a block special file.
    :c  File is a character special file.
    :t  Filehandle is opened to a tty.

    :u  File has setuid bit set.
    :g  File has setgid bit set.
    :k  File has sticky bit set.

Each of these is redirected (by Pair.ACCEPTS) to the corresponding method name on an IO object. (These methods are not defined on bare strings). Each test returns a boolean, and may be negated with a ! after the colon. They maybe ANDed and ORed using junctional logic. In fact, this is the primary reason for writing them as a pattern match; if you only want one test, you could just call the individual IO method directly and more efficiently. In any case, you must call the .s method to return the file's size in bytes.

There is no <.z> method, so just write :!s to test a file for zero size. Likewise, just call .s directly if you actually want to know the file's size, since ~~ :s only returns a boolean.

The .T and .B methods will be replaced by some filetype guessing methods more appropriate to the age of Unicode. There are likely methods to return the various ages of the file corresponding to Perl 5's -M, -A, and -C times, but they make no sense as booleans, so also call those methods directly (whatever they end up being named).

The interpretation of the file permission operators :r, :R, :w, :W, :x, and :X is by default based on:

  • The mode of the file and the uids and gids of the user

  • ACLs (access control lists)

  • read-only filesystems

There may be other reasons you can't actually read, write, or execute the file. Such reasons may be for example network filesystem access controls and unrecognized executable formats.

Also note that, for the superuser on the local filesystems, the :r, :R, :w, and :W tests always return 1, and :x and :X return 1 if any execute bit is set in the mode. Scripts run by the superuser may thus need to do a stat to determine the actual mode of the file, or temporarily set their effective uid to something else.

You can test multiple features using junctions:

  if $filename.IO ~~ :r & :w & :x  {...}


This is a basic abstraction; for better control, use the operating-system specific interfaces, over which this is a thin veneer.

    class IO::ACL {
        has Str $.type; # "User", "Group", "Everyone", ???
        has Str $.id; # username or groupname; unused for $type eq "Everyone"
        has %.permissions;
                # Unsupported values may (or may not) throw
                # UnsupportedPermission when set or read
        has Path $.owningObject;

The permissions used in %permissions are:


Should be supported by all filesystems as an item to read from the hash for the group "Everyone".


Should be supported by all filesystems as an item to read from the hash for the group "Everyone".


Supported on most Unix systems, anyway. Windows should be able to guess when this is read, and throw an exception if written to.


An ACL of User,fred,Default sets the user "fred" to be the owner of the file. This can be done with groups too. Works on Unix, at least.

The $.owningObject attribute of ACL shows what the ACL is set on. On a Windows system, this can be a parent directory, as permissions are inherited.


    class IO::Socket::INET does IO::Socket {
        has Int $.Version = 4; # Whether to use IPv4 or IPv6
        has Str $.Protocol = 'TCP';
        has Str $.RemoteHost;
        has Int $.RemotePort;
        has Str $.LocalHost;
        has Int $.LocalPort;
    method new(
        Str  :$RemoteHost, # Initialises $.RemoteHost
        Str  :$RemotePort, # Initialises $.RemotePort (if it's not a numeric string, use getservbyname)
        Str  :$LocalHost,  # Initialises $.LocalHost
        Str  :$LocalPort,  # Initialises $.LocalPort (if it's not a numeric string, use getservbyname)
        Str  :$Protocol,   # Initialises $.Protocol
        Int  :$Version,    # Initialises $.Version (IPv4 vs. IPv6)

        Bool :$Listener,   # Passed to

        Bool :$Blocking,   # Passed to
        Bool :$NoOpen,     # Passed to

        --> IO::Socket::INET
    ) {...}


    class IO::Pipe does IO::Streamable does IO::Readable does IO::Writable {

Will need to set IO::Readable.isReadable and IO::Writable.isWriteable depending on opening method.


If the file handle came from a piped open, close will additionally return Failure (aliased to $!) if one of the other system calls involved fails, or if the program exits with non-zero status. The exception object will contain any pertinent information. Closing a pipe also waits for the process executing on the pipe to complete, in case you want to look at the output of the pipe afterwards, and implicitly puts the exit status value into the Failure object if necessary.
    method to(Str $command, *%opts --> Bool)
    method to(Str *@command, *%opts --> Bool)

Opens a one-way pipe writing to $command. IO redirection for stderr is specified with :err(IO) or :err<Str>. Other IO redirection is done with feed operators. XXX how to specify "2>&1"?

    method from(Str $command, *%opts --> Bool)
    method from(Str *@command, *%opts --> Bool)

Opens a one-way pipe reading from $command. IO redirection for stderr is specified with :err(IO) or :err<Str>. Other IO redirection is done with feed operators. XXX how to specify "2>&1"?

    method pair(--> List of IO::Pipe)

A wrapper for pipe(2), returns a pair of IO objects representing the reader and writer ends of the pipe.

   ($r, $w) = IO::Pipe.pair;

OS-specific classes



    multi chown ($uid = -1, $gid = -1, *@files --> Int)

Changes the owner (and group) of a list of files. The first two elements of the list must be the numeric uid and gid, in that order. A value of -1 in either position is interpreted by most systems to leave that value unchanged. Returns the number of files successfully changed.

    $count = chown $uid, $gid, 'foo', 'bar';
    chown $uid, $gid, @filenames;

On systems that support fchown, you might pass file handles among the files. On systems that don't support fchown, passing file handles produces a fatal error at run time.

Here's an example that looks up nonnumeric uids in the passwd file:

   $user = prompt "User: ";
   $pattern = prompt "Files: ";

   ($login,$pass,$uid,$gid) = getpwnam($user)
       or die "$user not in passwd file";

   @ary = glob($pattern);      # expand filenames
   chown $uid, $gid, @ary;

On most systems, you are not allowed to change the ownership of the file unless you're the superuser, although you should be able to change the group to any of your secondary groups. On insecure systems, these restrictions may be relaxed, but this is not a portable assumption. On POSIX systems, you can detect this condition this way:

    use POSIX qw(sysconf _PC_CHOWN_RESTRICTED);
    $can-chown-giveaway = not sysconf(_PC_CHOWN_RESTRICTED);
chmod LIST

Changes the permissions of a list of files. The first element of the list must be the numerical mode, which should probably be an octal number, and which definitely should not be a string of octal digits: 0o644 is okay, 0644 is not. Returns the number of files successfully changed.

    $count = chmod 0o755, 'foo', 'bar';
    chmod 0o755, @executables;
    $mode = '0644'; chmod $mode, 'foo';      # !!! sets mode to --w----r-T
    $mode = '0o644'; chmod $mode, 'foo';     # this is better
    $mode = 0o644;   chmod $mode, 'foo';     # this is best
    $node.stat(Bool :$link); # :link does an lstat instead

Returns a stat buffer. If the lstat succeeds, the stat buffer evaluates to true, and additional file tests may be performed on the value. If the stat fails, all subsequent tests on the stat buffer also evaluate to false.


    role IO::Socket::Unix does IO::Socket {
        has Str $.RemoteAddr, # Remote Address
        has Str $.LocalAddr,  # Local Address
    method new(
        Str  :$RemoteAddr,
        Str  :$LocalAddr,

        Bool :$Listener,   # Passed to

        Bool :$Blocking,   # Passed to
        Bool :$NoOpen,     # Passed to

        --> IO::Socket::Unix
    ) {...}
    method pair(Int $domain, Int $type, Int $protocol --> List of IO)

A wrapper for socketpair(2), returns a pair of IO objects representing the reader and writer ends of the socket.

   use IO::Socket;
   ($r, $w) = IO::Socket::Unix.pair(AF_UNIX, SOCK_STREAM, PF_UNSPEC);


Indicates that this object can perform standard posix IO operations. It implies IO::Readable and IO::Writeable.

method dup( --> IO)
has Bool $.blocking is rw
method flock(:$r,:$w --> Bool)
method funlock( --> Bool)



Available only as a handle method.

    multi prompt (Str $prompt --> Str)

Should there be an IO::Interactive role?


Removed functions


Gone, see eoi IO::Seekable.


See IO::FileDescriptor.


Should be implemented by an external library.


Use stat with the :link option.

Changed to .path, but we haven't gotten around to specifying this on all of them.

The .name method returns the name of the file/socket/uri the handle was opened with, if known. Returns Nil otherwise. There is no corresponding name() function.


Gone, see Pipe.pair


Gone. (Note: for sub-second sleep, just use sleep with a fractional argument.)


Gone, see IO::Socket.close(), $IO::Readable.isReadable, and $IO::Writeable.isWriteable


Gone, see Socket.pair


Gone, see


Gone, see


Gone, see Path.times.


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