class IO::ArgFiles
Iterate over contents of files specified on command line
is IO::CatHandle
This class exists for backwards compatibility reasons and provides no additional methods to IO::CatHandle
, so it can be used in the same way as it, for instance, in this way:
my = IO::ArgFiles.new();.say for .lines;
If invoked with perl6 io-argfiles.p6 *.p6
it will print the contents of all the files with that extension in the directory. However, that is totally equivalent to:
my = IO::CatHandle.new();.say for .lines;
Variables
$*ARGFILES
This class is the magic behind the $*ARGFILES
variable, which provides a way to iterate over files passed in to the program on the command line (i.e. elements of @*ARGS
). Thus the examples above can be simplified like so:
.say for .lines;# orwhile ! .eof# orsay .slurp;
Save one of the variations above in a file, say argfiles.p6
. Then create another file (named, say sonnet18.txt
with the contents:
Shall I compare thee to a summer's day?
Running the command
$ perl6 argfiles.p6 sonnet18.txt
will then give the output
Shall I compare thee to a summer's day?
As of 6.d language, $*ARGFILES
inside sub MAIN
is always set to $*IN
, even when @*ARGS
is not empty. That means that
sub MAIN ()
which can be used as cat *.p6 | perl6 argfiles-main.p6
, for instance, is totally equivalent to:
sub MAIN ()
and, in fact, can't be used to process the arguments in the command line, since, in this case, it would result in an usage error.
Bear in mind that the object $*ARGFILES
is going to contain a handle for every argument in a command line, even if that argument is not a valid file. You can retrieve them via the .handles
method.
for .handles ->
That code will fail if any of the arguments is not the valid name of a file. You will have to deal with that case at another level, checking that @*ARGS
contains valid file names, for instance.
Type Graph
Routines supplied by class IO::CatHandle
IO::ArgFiles inherits from class IO::CatHandle, which provides the following routines:
(IO::CatHandle) method new
Defined as:
method new(*, :, : = True,: = ["\n", "\r\n"], Str :, Bool :)
Creates a new IO::CatHandle object.
The @handles
positional argument indicates a source of handles for the IO::CatHandle
to read from and can deal with a mixed collection of Cool, IO::Path, and IO::Handle (including IO::Pipe) objects. As input from IO::CatHandle is processed (so operations won't happen during .new
call, but only when @handles
' data is needed), it will walk through the @handles
list, processing each argument as follows:
IO::Path objects will be opened for reading using the IO::CatHandle's (invocant's) attributes for open
calls;
un-opened IO::Handle objects will be opened in the same fashion as IO::Path objects;
and already opened IO::Handle objects will have all of their attributes set to the attributes of the invocant IO::CatHandle.
In short, all the @handles
end up as IO::Handle objects opened in the same mode and with the same attributes as the invocant IO::CatHandle.
See .on-switch
method for details on the :&on-switch
named argument, which by default is not set.
The :$encoding
named argument specifies the handle's encoding and accepts the same values as IO::Handle.encoding
. Set :$bin
named argument to True
if you wish the handle to be in binary mode. Attempting to specify both a defined :$encoding
and a True
:$bin
is a fatal error resulting in X::IO::BinaryAndEncoding
exception thrown. If neither :$encoding
is set nor :$bin
set to a true value, the handle will default to utf8
encoding.
The :$chomp
and :$nl-in
arguments have the same meaning as in IO::Handle and take and default to the same values.
(IO::CatHandle) method chomp
Defined as:
method chomp(IO::CatHandle:) is rw
Sets the invocant's $.chomp
attribute to the assigned value. All source handles, including the active one will use the provided $.chomp
value.
(my = 'foo'.IO).spurt: "A\nB\nC\n";(my = 'bar'.IO).spurt: "D\nE\n";with IO::CatHandle.new: ,
(IO::CatHandle) method nl-in
Defined as:
method nl-in(IO::CatHandle:) is rw
Sets the invocant's $.nl-in
attribute to the assigned value, which can be a Str or a List of Str, where each Str object represents the end-of-line string. All source handles, including the active one will use the provided $.nl-in
value. Note that source handle boundary is always counted as a new line break.
(my = 'foo'.IO).spurt: "A\nB\nC";(my = 'bar'.IO).spurt: "DxEx";with IO::CatHandle.new: ,
(IO::CatHandle) method close
Defined as:
method close(IO::CatHandle: --> True)
Closes the currently active source handle, as well as any already-open source handles, and empties the source handle queue. Unlike a regular IO::Handle, an explicit call to .close
is often not necessary on a CatHandle, as merely exhausting all the input closes all the handles that need to be closed.
with IO::CatHandle.new:
(IO::CatHandle) method comb
Defined as:
method comb(IO::CatHandle: |args --> Seq)
Read the handle and processes its contents the same way Str.comb
does, taking the same arguments. Implementations may slurp the contents of all the source handles in their entirety when this method is called.
(my = 'foo'.IO).spurt: 'foo';(my = 'bar'.IO).spurt: 'bar';IO::CatHandle.new(, ).comb(2).perl.say;# OUTPUT: «("fo", "ob", "ar").Seq»
(IO::CatHandle) method DESTROY
Defined as:
method DESTROY(IO::CatHandle:)
Calls .close
. This method isn't to be used directly, but is something that's called during garbage collection.
(IO::CatHandle) method encoding
Defined as:
multi method encoding(IO::CatHandle:)multi method encoding(IO::CatHandle: )
Sets the invocant's $.encoding
attribute to the provided value. Valid values are the same as those accepted by IO::Handle.encoding
(use value Nil to switch to binary mode). All source handles, including the active one will use the provided $.encoding
value.
(my = 'foo'.IO).spurt: 'I ♥ Perl';(my = 'bar'.IO).spurt: 'meow';with IO::CatHandle.new: ,
(IO::CatHandle) method eof
Defined as:
method eof(IO::CatHandle: --> Bool)
Returns True
if the read operations have exhausted the source handle queue, including the contents of the last handle. Note: calling this method may cause one or more .on-switch
calls, while the source handle queue is examined, and the source handle queue may get exhausted.
(my = 'foo'.IO).spurt: 'foo';(my = 'bar'.IO).spurt: 'bar';with IO::CatHandle.new: :on-switch, ,
The same caveats for non-seekable handles and empty files that apply to IO::Handle.eof apply here.
(IO::CatHandle) method get
Defined as:
method get(IO::CatHandle: --> Bool)
Returns a single line of input from the handle, with the new line string defined by the value(s) of $.nl-in
attribute, which will be removed from the line if $.chomp
attribute is set to True
. Returns Nil
when there is no more input. It is an error to call this method when the handle is in binary mode, resulting in X::IO::BinaryMode
exception being thrown.
(my = 'foo'.IO).spurt: "a\nb\nc";(my = 'bar'.IO).spurt: "d\ne";my = IO::CatHandle.new: , ;.say while = .get; # OUTPUT: «abcde»
(IO::CatHandle) method getc
Defined as:
method getc(IO::CatHandle: --> Bool)
Returns a single character of input from the handle. All the caveats described in IO::Handle.getc
apply. Returns Nil
when there is no more input. It is an error to call this method when the handle is in binary mode, resulting in X::IO::BinaryMode
exception being thrown.
(my = 'foo'.IO).spurt: 'I ♥ Perl';(my = 'bar'.IO).spurt: 'meow';my = IO::CatHandle.new: , ;.say while = .getc; # OUTPUT: «I ♥ Perlmeow»
(IO::CatHandle) method handles
Defines as:
method handles(IO::CatHandle: --> Seq)
Returns a Seq containing the currently-active handle, as well as all the remaining source handles produced by calling next-handle. If the invocant has already been fully-consumed, returns an empty Seq.
This method is especially handy when working with IO::ArgFiles, where you want to treat each filehandle separately:
# print at most the first 2 lines of each file in $*ARGFILES:.say for flat .handles.map: *.lines: 2
It is acceptable to call this method multiple times; .handles.head
is a valid idiom for obtaining the currently-active handle. If, between reification of the elements of the returned Seq the handles get switched by some other means, the next element produced by the Seq would be the next handle of the invocant, not the handle that would've been produced if no switching occurred:
(my := 'file1'.IO).spurt: "1a\n1b\n1c";(my := 'file2'.IO).spurt: "2a\n2b\n2c";(my := 'file3'.IO).spurt: "3a\n3b\n3c";my := IO::CatHandle.new: , , ;for .handles# OUTPUT: «(1a 1b)(3a 3b)»
Likewise, reifying the returned Seq consumes the invocant's source handles and once it is fully reified the invocant becomes fully-consumed.
(IO::CatHandle) method IO
Defined as:
method IO(IO::CatHandle:)
Alias for .path
(IO::CatHandle) method lines
Defined as:
method lines(IO::CatHandle: = Inf, : --> Seq)
Same as IO::Handle.lines
. Note that a boundary between source handles is considered to be a newline break.
(my = 'foo'.IO).spurt: "foo\nbar";(my = 'bar'.IO).spurt: 'meow';IO::CatHandle.new(, ).lines.perl.say;# OUTPUT: «("foo", "bar", "meow").Seq»
Note: if :$close
is False
, fully-consumed handles are still going to be closed.
(IO::CatHandle) method lock
Defined as:
method lock(IO::CatHandle: Bool : = False, Bool : = False --> True)
Same as IO::Handle.lock
. Returns Nil if the source handle queue has been exhausted.
Locks only the currently active source handle. The .on-switch
Callable can be used to conveniently lock/unlock the handles as they're being processed by the CatHandle.
(IO::CatHandle) method native-descriptor
Defined as:
method native-descriptor(IO::CatHandle: --> Int)
Returns the native-descriptor of the currently active source handle or Nil if the source handle queue has been exhausted.
Since the CatHandle
closes a source handle, once it's done with it, it's possible for successive source handles to have the same native descriptor, if they were passed to .new as Cool or IO::Path objects.
(my = 'foo'.IO).spurt: 'foo';(my = 'bar'.IO).spurt: 'bar';with IO::CatHandle.new: , ,
(IO::CatHandle) method next-handle
Defined as:
method next-handle(IO::CatHandle: --> IO::Handle)
Switches the active source handle to the next handle in the source handle queue, which is the sources given in @handles
attribute to .new
. The return value is the currently active source handle or Nil
if the source handle queue has been exhausted.
Coerces Cool source "handles" to IO::Path; opens IO::Path and unopened IO::Handle source handles for reading using the invocant's $.nl-in
, $.chomp
, and $.encoding
attributes; those same attributes of already-opened IO::Handle objects will be changed to the values of the invocant's attributes.
This method is called automatically whenever CatHandle's methods require a switch to the next source handle, triggers .on-switch
Callable to be called, and is called once during .new call. The .on-switch
will continue to be triggered each time this method is called, even after the source handle queue has been exhausted. Note that generally reaching the EOF of the currently active source handle does not trigger the .next-handle
call, but rather further read operations that need more data do.
(my = 'foo'.IO).spurt: "a\nb";(my = 'bar'.IO).spurt: "c\nd";with IO::CatHandle.new: :on-switch, ,
(IO::CatHandle) method on-switch
Defined as:
has is rw
One of the attributes that can be set during .new
call and changed later by assigning to. By default is not specified. Takes a Callable with .count
of 0
, 1
, 2
, or Inf
. Gets called every time .next-handle
is, which happens once during .new
call and then each time a source handle is switched to the next one in the queue, or when the .next-handle
method is called manually.
If the .count
of &.on-switch
is 0
, it receives no arguments; if it's 1
, it receives the currently active handle, and if it's 2
or Inf
, it receives the currently active handle, and the last active handle as positional arguments (in that order). On the very first &.on-switch
execution, the "last active handle" argument is Nil
. Upon source handle queue exhaustion the "currently active handle" argument is Nil
, and all the executions made afterwards have both arguments as Nil
.
(my = 'foo'.IO).spurt: "A\nB\nC";(my = 'bar'.IO).spurt: "D\nE";my ;my = IO::CatHandle.new: :on-switch, , ;say ": $_" for .lines;# OUTPUT:# foo:1 A# foo:2 B# foo:3 C# bar:1 D# bar:2 E
my ;sub on-switch (, )(my = 'foo'.IO).spurt: "A\nB\nC";(my = 'bar'.IO).spurt: "D\nE";my = IO::CatHandle.new: :, , ;.lines.perl.say; # OUTPUT: «("", "B", "C", "", "E").Seq».perl.say; # OUTPUT: «["A\nB\nC", "D\nE"]»
(IO::CatHandle) method open
Defined as:
method open(IO::CatHandle: --> IO::CatHandle)
Returns the invocant. The intent of this method is to merely make CatHandle workable with things that open IO::Handle. You never have to call this method intentionally.
(IO::CatHandle) method opened
Defined as:
method opened(IO::CatHandle: --> Bool)
Returns True
if the invocant has any source handles, False
otherwise.
say IO::CatHandle.new .opened; # OUTPUT: «False»say IO::CatHandle.new().opened; # OUTPUT: «True»(my = 'foo'.IO).spurt: "A\nB\nC";with IO::CatHandle.new:
(IO::CatHandle) method path
Defined as:
method path(IO::CatHandle:)
Returns the value of .path
attribute of the currently active source handle, or Nil if the source handle queue has been exhausted. Basically, if your CatHandle is based on files, this is the way to get the path of the file the CatHandle is currently reading from.
(my = 'foo'.IO).spurt: "A\nB\nC";(my = 'bar'.IO).spurt: "D\nE";my ;my = IO::CatHandle.new: :on-switch, , ;say ": $_" for .lines;# OUTPUT:# foo:1 A# foo:2 B# foo:3 C# bar:1 D# bar:2 E
(IO::CatHandle) method read
Defined as:
method read(IO::CatHandle: Int(Cool) = 65536 --> Buf)
Reads up to $bytes
bytes from the handle and returns them in a Buf. $bytes
defaults to an implementation-specific value (in Rakudo, the value of $*DEFAULT-READ-ELEMS
, which by default is set to 65536
). It is permitted to call this method on handles that are not in binary mode.
(my = 'foo'.IO).spurt: 'meow';(my = 'bar'.IO).spurt: Blob.new: 4, 5, 6;with IO::CatHandle.new: :bin, ,# Non-binary mode is OK too:with IO::CatHandle.new: ,
(IO::CatHandle) method readchars
Defined as:
method readchars(IO::CatHandle: Int(Cool) = 65536 --> Str)
Returns a Str of up to $chars
characters read from the handle. $chars
defaults to an implementation-specific value (in Rakudo, the value of $*DEFAULT-READ-ELEMS
, which by default is set to 65536
). It is NOT permitted to call this method on handles opened in binary mode and doing so will result in X::IO::BinaryMode
exception being thrown.
(my = 'foo'.IO).spurt: 'Perl loves to';(my = 'bar'.IO).spurt: ' meow';with IO::CatHandle.new: ,
(IO::CatHandle) method seek
Defined as:
method seek(IO::CatHandle: |c)
Calls .seek
on the currently active source handle, forwarding it all the arguments, and returns the result. Returns Nil if the source handle queue has been exhausted. NOTE: this method does NOT perform any source handle switching, so seeking past the end of the current source handle will NOT seek to the next source handle in the queue and seeking past the beginning of the current source handle is a fatal error. Also see .next-handle
, to learn the details on when source handles are switched.
(my = 'foo'.IO).spurt: 'foo';(my = 'bar'.IO).spurt: 'bar';with IO::CatHandle.new: ,
(IO::CatHandle) method tell
Defined as:
method tell(IO::CatHandle: --> Int)
Calls .tell
on the currently active source handle and returns the result. Returns Nil if the source handle queue has been exhausted.
(my = 'foo'.IO).spurt: 'foo';(my = 'bar'.IO).spurt: 'bar';with IO::CatHandle.new: ,
(IO::CatHandle) method slurp
Defined as:
method slurp(IO::CatHandle:)
Reads all of the available input from all the source handles and returns it as a Buf if the handle is in binary mode or as a Str otherwise. Returns Nil if the source handle queue has been exhausted.
(my = 'foo'.IO).spurt: 'foo';(my = 'bar'.IO).spurt: 'bar';IO::CatHandle.new( , ).slurp.say; # OUTPUT: «foobar»IO::CatHandle.new(:bin, , ).slurp.say; # OUTPUT: «Buf[uint8]:0x<66 6f 6f 62 61 72>»IO::CatHandle.new .slurp.say; # OUTPUT: «Nil»
(IO::CatHandle) method split
Defined as:
method split(IO::CatHandle: |args --> Seq)
Read the handle and processes its contents the same way Str.split
does, taking the same arguments. Implementations may slurp the contents of all the source handles in their entirety when this method is called.
(my = 'foo'.IO).spurt: 'foo';(my = 'bar'.IO).spurt: 'bar';IO::CatHandle.new(, ).split(/o+/).perl.say;# OUTPUT: «("f", "bar").Seq»
(IO::CatHandle) method Str
Defined as:
method Str(IO::CatHandle: --> Str)
Calls .Str
on the currently active source handle and returns the result. If the source handle queue has been exhausted, returns an implementation-defined string ('<closed IO::CatHandle>'
in Rakudo).
(IO::CatHandle) method Supply
Defined as:
method Supply(IO::CatHandle: : = 65536 --> Supply)
Returns a Supply fed with either .read
, if the handle is in binary mode, or with .readchars
, if it isn't, with reads of :$size
bytes or characters. :$size
defaults to an implementation-specific value (in Rakudo, the value of $*DEFAULT-READ-ELEMS
, which by default is set to 65536
).
(my = 'foo'.IO).spurt: 'foo';(my = 'bar'.IO).spurt: 'bar';react whenever IO::CatHandle.new(, ).Supply: :2size# OUTPUT: «foobar»react whenever IO::CatHandle.new(:bin, , ).Supply: :2size# OUTPUT: «Buf[uint8]:0x<66 6f>Buf[uint8]:0x<6f 62>Buf[uint8]:0x<61 72>»
(IO::CatHandle) method t
Defined as:
method t(IO::CatHandle: --> Bool)
Calls .t
, which tells if the handle is a TTY, on the currently active source handle and returns the result. If the source handle queue has been exhausted, returns False
.
(my = 'foo'.IO).spurt: 'foo';with IO::CatHandle.new: ,
(IO::CatHandle) method unlock
Defined as:
method unlock(IO::CatHandle:)
Same as IO::Handle.unlock
. Returns Nil if the source handle queue has been exhausted.
Unlocks only the currently active source handle. The .on-switch
Callable can be used to conveniently lock/unlock the handles as they're being processed by the CatHandle.
(IO::CatHandle) method words
Defined as:
method words(IO::CatHandle: = Inf, : --> Seq)
Same as IO::Handle.words
(including the caveat about more data read than needed to make some number of words). Note that a boundary between source handles is considered to be word boundary.
(my = 'foo'.IO).spurt: 'foo bar';(my = 'bar'.IO).spurt: 'meow';IO::CatHandle.new(, ).words.perl.say;# OUTPUT: «("foo", "bar", "meow").Seq»
Note: if :$close
is False
, fully-consumed handles are still going to be closed.
(IO::CatHandle) method flush
Defined as:
multi method flush(|)
The IO::CatHandle type overrides this method to throw a X::NYI
exception. If you have a good idea for how this method should behave, tell Rakudo developers about it!
(IO::CatHandle) method nl-out
Defined as:
multi method nl-out(|)
The IO::CatHandle type overrides this method to throw a X::NYI
exception. If you have a good idea for how this method should behave, tell Rakudo developers about it!
(IO::CatHandle) method out-buffer
Defined as:
multi method out-buffer(|)
The IO::CatHandle type overrides this method to throw a X::NYI
exception. If you have a good idea for how this method should behave, tell Rakudo developers about it!
(IO::CatHandle) method print
Defined as:
multi method print(|)
The IO::CatHandle type overrides this method to throw a X::NYI
exception. If you have a good idea for how this method should behave, tell Rakudo developers about it!
(IO::CatHandle) method printf
Defined as:
multi method printf(|)
The IO::CatHandle type overrides this method to throw a X::NYI
exception. If you have a good idea for how this method should behave, tell Rakudo developers about it!
(IO::CatHandle) method print-nl
Defined as:
multi method print-nl(|)
The IO::CatHandle type overrides this method to throw a X::NYI
exception. If you have a good idea for how this method should behave, tell Rakudo developers about it!
(IO::CatHandle) method put
Defined as:
multi method put(|)
The IO::CatHandle type overrides this method to throw a X::NYI
exception. If you have a good idea for how this method should behave, tell Rakudo developers about it!
(IO::CatHandle) method say
Defined as:
multi method say(|)
The IO::CatHandle type overrides this method to throw a X::NYI
exception. If you have a good idea for how this method should behave, tell Rakudo developers about it!
(IO::CatHandle) method write
Defined as:
multi method write(|)
The IO::CatHandle type overrides this method to throw a X::NYI
exception. If you have a good idea for how this method should behave, tell Rakudo developers about it!
(IO::CatHandle) method WRITE
Defined as:
multi method WRITE(|)
The IO::CatHandle type overrides this method to throw a X::NYI
exception. If you have a good idea for how this method should behave, tell Rakudo developers about it!
(IO::CatHandle) method READ
Defined as:
multi method EOF(|)
The IO::CatHandle type overrides this method to throw a X::NYI
exception. If you have a good idea for how this method should behave, tell Rakudo developers about it!
(IO::CatHandle) method EOF
Defined as:
multi method EOF(|)
The IO::CatHandle type overrides this method to throw a X::NYI
exception. If you have a good idea for how this method should behave, tell Rakudo developers about it!
Routines supplied by class IO::Handle
IO::ArgFiles inherits from class IO::Handle, which provides the following routines:
(IO::Handle) method open
Defined as:
method open(IO::Handle::, :, :, :, Str :,Str :,:, :, :, :, :, :, :, :,:, :, :, :,:,--> IO::Handle)
Opens the handle in one of the modes. Fails with appropriate exception if the open fails.
See description of individual methods for the accepted values and behavior of :$chomp
, :$nl-in
, :$nl-out
, and :$enc
. The values for parameters default to the invocant's attributes and if any of them are provided, the attributes will be updated to the new values. Specify :$bin
set to True
instead of :$enc
to indicate the handle should be opened in binary mode. Specifying undefined value as :$enc
is equivalent to not specifying :$enc
at all. Specifying both a defined encoding as :$enc
and :$bin
set to true will cause X::IO::BinaryAndEncoding
exception to be thrown.
The open mode defaults to non-exclusive, read only (same as specifying :r
) and can be controlled by a mix of the following arguments:
:r same as specifying :mode<ro> same as specifying nothing:w same as specifying :mode<wo>, :create, :truncate:a same as specifying :mode<wo>, :create, :append:x same as specifying :mode<wo>, :create, :exclusive:update same as specifying :mode<rw>:rw same as specifying :mode<rw>, :create:ra same as specifying :mode<rw>, :create, :append:rx same as specifying :mode<rw>, :create, :exclusive
Support for combinations of modes other than what is listed above is implementation-dependent and should be assumed unsupported. That is, specifying, for example, .open(:r :create)
or .open(:mode<wo> :append :truncate)
might work or might cause the Universe to implode, depending on a particular implementation. This applies to reads/writes to a handle opened in such unsupported modes as well.
The mode details are:
:mode<ro> means "read only":mode<wo> means "write only":mode<rw> means "read and write":create means the file will be created, if it does not exist:truncate means the file will be emptied, if it exists:exclusive means .open will fail if the file already exists:append means writes will be done at the end of file's current contents
Attempts to open a directory, write to a handle opened in read-only mode or read from a handle opened in write-only mode, or using text-reading methods on a handle opened in binary mode will fail or throw.
In 6.c language, it's possible to open path '-'
, which will cause open
to open (if closed
) the $*IN
handle if opening in read-only mode or to open the $*OUT
handle if opening in write-only mode. All other modes in this case will result in exception being thrown.
As of 6.d language version, use path '-'
is deprecated and it will be removed in future language versions entirely.
The :out-buffer
controls output buffering and by default behaves as if it were Nil
. See method out-buffer for details.
Note (Rakudo versions before 2017.09): Filehandles are NOT flushed or closed when they go out of scope. While they will get closed when garbage collected, garbage collection isn't guaranteed to get run. This means you should use an explicit close
on handles opened for writing, to avoid data loss, and an explicit close
is recommended on handles opened for reading as well, so that your program does not open too many files at the same time, triggering exceptions on further open
calls.
Note (Rakudo versions 2017.09 and after): Open filehandles are automatically closed on program exit, but it is still highly recommended that you close
opened handles explicitly.
(IO::Handle) method comb
Defined as:
method comb(IO::Handle: Bool :, |args --> Seq)
Read the handle and processes its contents the same way Str.comb
does, taking the same arguments, closing the handle when done if $close
is set to a true value. Implementations may slurp the file in its entirety when this method is called.
Attempting to call this method when the handle is in binary mode will result in X::IO::BinaryMode
exception being thrown.
my = 'path/to/file'.IO.open;say "The file has ♥s in it";
(IO::Handle) method chomp
Defined as:
has is rw = True
One of the attributes that can be set via .new
or open. Defaults to True
. Takes a Bool specifying whether the line separators (as defined by .nl-in
) should be removed from content when using .get
or .lines
methods.
(IO::Handle) routine get
Defined as:
method get(IO::Handle: --> Str)multi sub get (IO::Handle = --> Str)
Reads a single line of input from the handle, removing the trailing newline characters (as set by .nl-in
) if the handle's .chomp
attribute is set to True
. Returns Nil
, if no more input is available. The subroutine form defaults to $*ARGFILES
if no handle is given.
Attempting to call this method when the handle is in binary mode will result in X::IO::BinaryMode
exception being thrown.
.get.say; # Read one line from the standard inputmy = open 'filename';.get.say; # Read one line from a file.close;say get; # Read one line from $*ARGFILES
(IO::Handle) routine getc
Defined as:
method getc(IO::Handle: --> Str)multi sub getc (IO::Handle = --> Str)
Reads a single character from the input stream. Attempting to call this method when the handle is in binary mode will result in X::IO::BinaryMode
exception being thrown. The subroutine form defaults to $*ARGFILES
if no handle is given. Returns Nil
, if no more input is available, otherwise operation will block, waiting for at least one character to be available; these caveats apply:
Buffering terminals
Using getc to get a single keypress from a terminal will only work properly if you've set the terminal to "unbuffered". Otherwise the terminal will wait for the return key to be struck or the buffer to be filled up before perl6 gets even a single byte of data.
Waiting for potential combiners
If your handle's encoding allows combining characters to be read, perl6 will wait for more data to be available before it provides a character. This means that inputting an "e" followed by a combining acute will give you an e with an acute rather than giving an "e" and letting the next reading function give you a dangling combiner. However, it also means that when the user inputs just an "e" and has no intention to also input a combining acute, your program will be waiting for another keypress before the initial "e" is returned.
(IO::Handle) submethod DESTROY
Defined as:
submethod DESTROY(IO::Handle:)
Closes the filehandle, unless its native-descriptor is 2
or lower. This ensures the standard filehandles do not get inadvertently closed.
Note that garbage collection is not guaranteed to happen, so you must NOT rely on DESTROY
for closing the handles you write to and instead close them yourself. Programs that open a lot of files should close the handles explicitly as well, regardless of whether they were open for writing, since too many files might get opened before garbage collection happens and the no longer used handles get closed.
(IO::Handle) method gist
Defined as:
method gist(IO::Handle: --> Str)
Returns a string containing information which .path
, if any, the handle is created for and whether it is .opened
.
say IO::Handle.new; # IO::Handle<(Any)>(closed)say "foo".IO.open; # IO::Handle<"foo".IO>(opened)
(IO::Handle) method eof
Defined as:
method eof(IO::Handle: --> Bool)
Non-blocking. Returns True
if the read operations have exhausted the contents of the handle. For seekable handles, this means current position is at or beyond the end of file and seeking an exhausted handle back into the file's contents will result in eof returning False
again.
On non-seekable handles and handles opened to zero-size files (including special files in /proc/
), EOF won't be set until a read operation fails to read any bytes. For example, in this code, the first read
consumes all of the data, but it's only until the second read
that reads nothing would the EOF on a TTY handle be set:
$ echo "x" | perl6 -e 'with $*IN { .read: 10000; .eof.say; .read: 10; .eof.say }'FalseTrue
(IO::Handle) method encoding
Defined as:
multi method encoding(IO::Handle: --> Str)multi method encoding(IO::Handle: --> Str)
Returns a Str representing the encoding currently used by the handle, defaulting to "utf8"
. Nil
indicates the filehandle is currently in binary mode. Specifying an optional positional $enc
argument switches the encoding used by the handle; specify Nil
as encoding to put the handle into binary mode.
The accepted values for encoding are case-insensitive. The available encodings vary by implementation and backend. On Rakudo MoarVM the following are supported:
utf8utf16utf16leutf16beutf8-c8iso-8859-1windows-1251windows-1252windows-932ascii
The default encoding is utf8, which undergoes normalization into Unicode NFC (normalization form canonical). In some cases you may want to ensure no normalization is done; for this you can use utf8-c8
. Before using utf8-c8
please read Unicode: Filehandles and I/O for more information on utf8-c8
and NFC.
As of Rakudo 2018.04 windows-932 is also supported which is a variant of ShiftJIS.
Implementation may choose to also provide support for aliases, e.g. Rakudo allows aliases latin-1
for iso-8859-1
encoding and dashed utf versions: utf-8
and utf-16
.
utf16, utf16le and utf16be
Unlike utf8, utf16 has an endianness — either big endian or little endian. This relates to the ordering of bytes. Computer CPUs also have an endianness. Perl 6's utf16
format specifier will use the endianness of host system when encoding. When decoding it will look for a byte order mark and if it is there use that to set the endianness. If there is no byte order mark it will assume the file uses the same endianness as the host system. A byte order mark is the codepoint U+FEFF which is ZERO WIDTH NO-BREAK SPACE. On utf16
encoded files the standard states if it exists at the start of a file it shall be interpreted as a byte order mark, not a U+FEFF codepoint.
While writing will cause a different file to be written on different endian systems, at the release of 2018.10 the byte order mark will be written out when writing a file and files created with the utf16 encoding will be able to be read on either big or little endian systems.
When using utf16be or utf16le encodings a byte order mark is not used. The endianness used is not affected by the host cpu type and is either big endian for utf16be or little endian for utf16le.
In keeping with the standard, a 0xFEFF byte at the start of a file is interpreted as a ZERO WIDTH NO-BREAK SPACE and not as a byte order mark. No byte order mark is written to files that use the utf16be or utf16le encodings.
As of Rakudo 2018.09 on MoarVM, utf16, utf16le and utf16be are supported. In 2018.10, writing to a file with utf16 will properly add a byte order mark (BOM).
Examples
with 'foo'.IO
(IO::Handle) routine lines
Defined as:
sub lines(IO::Handle = , = Inf, : --> Seq)method lines(IO::Handle: = Inf, : --> Seq)
Return a Seq each element of which is a line from the handle (that is chunks delineated by .nl-in
). If the handle's .chomp
attribute is set to True
, then characters specified by .nl-in
will be stripped from each line.
Reads up to $limit
lines, where $limit
can be a non-negative Int, Inf
, or Whatever (which is interpreted to mean Inf
). If :$close
is set to True
, will close the handle when the file ends or $limit
is reached. Subroutine form defaults to $*ARGFILES
, if no handle is provided.
Attempting to call this method when the handle is in binary mode will result in X::IO::BinaryMode
exception being thrown.
NOTE: the lines are read lazily, so ensure the returned Seq is either fully reified or is no longer needed when you close the handle or attempt to use any other method that changes the file position.
say "The file contains ",'50GB-file'.IO.open.lines.grep(*.contains: 'Perl').elems," lines that mention Perl";# OUTPUT: «The file contains 72 lines that mention Perl»
(IO::Handle) method lock
Defined as:
method lock(IO::Handle: Bool : = False, Bool : = False --> True)
Places an advisory lock on the filehandle. If :$non-blocking
is True
will fail
with X::IO::Lock
if lock could not be obtained, otherwise will block until the lock can be placed. If :$shared
is True
will place a shared (read) lock, otherwise will place an exclusive (write) lock. On success, returns True
; fails with X::IO::Lock
if lock cannot be placed (e.g. when trying to place a shared lock on a filehandle opened in write mode or trying to place an exclusive lock on a filehandle opened in read mode).
You can use lock
again to replace an existing lock with another one. To remove a lock, close
the filehandle or use unlock
.
# One program writes, the other reads, and thanks to locks either# will wait for the other to finish before proceeding to read/write# Writergiven "foo".IO.open(:w)# Readergiven "foo".IO.open
(IO::Handle) method unlock
Defined as:
method unlock(IO::Handle: --> True)
Removes a lock
from the filehandle.
(IO::Handle) routine words
Defined as:
multi sub words(IO::Handle = , = Inf, : --> Seq)multi method words(IO::Handle: = Inf, : --> Seq)
Similar to Str.words
, separates the handle's stream on contiguous chunks of whitespace (as defined by Unicode) and returns a Seq of the resultant "words." Takes an optional $limit
argument that can be a non-negative Int, Inf
, or Whatever (which is interpreted to mean Inf
), to indicate only up-to $limit
words must be returned. If Bool :$close
named argument is set to True
, will automatically close the handle when the returned Seq is exhausted. Subroutine form defaults to $*ARGFILES
, if no handle is provided.
Attempting to call this method when the handle is in binary mode will result in X::IO::BinaryMode
exception being thrown.
my := bag .words;say "Most common words: ", .sort(-*.value).head: 5;
NOTE: implementations may read more data than necessary when a call to .words
is made. That is, $handle.words(2)
may read more data than two "words" worth of data and subsequent calls to read methods might not read from the place right after the two fetched words. After a call to .words
, the file position should be treated as undefined.
(IO::Handle) method split
Defined as:
method split(IO::Handle: :, |c)
Slurps the handle's content and calls Str.split
on it, forwarding any of the given arguments. If :$close
named parameter is set to True
, will close the invocant after slurping.
Attempting to call this method when the handle is in binary mode will result in X::IO::BinaryMode
exception being thrown.
my = 'path/to/file'.IO.open;.split: '♥', :close; # Returns file content split on ♥
(IO::Handle) method spurt
Defined as:
multi method spurt(IO::Handle: Blob , : = False)multi method spurt(IO::Handle: Cool , : = False)
Writes all of the $data
into the filehandle, closing it when finished, if $close
is True
. For Cool
$data
, will use the encoding the handle is set to use (IO::Handle.open
or IO::Handle.encoding
).
Behavior for spurting a Cool
when the handle is in binary mode or spurting a Blob
when the handle is NOT in binary mode is undefined.
(IO::Handle) method print
Defined as:
multi method print(** --> True)multi method print(Junction --> True)
Writes the given @text
to the handle, coercing any non-Str objects to Str by calling .Str
method on them. Junction arguments autothread and the order of printed strings is not guaranteed. See write to write bytes.
Attempting to call this method when the handle is in binary mode will result in X::IO::BinaryMode
exception being thrown.
my = 'path/to/file'.IO.open: :w;.print: 'some text';.close;
(IO::Handle) method print-nl
Defined as:
method print-nl(IO::Handle: --> True)
Writes the value of $.nl-out
attribute into the handle. This attribute, by default, is 
, but see the page on newline for the rules it follows in different platforms and environments.
Attempting to call this method when the handle is in binary mode will result in X::IO::BinaryMode
exception being thrown.
my = 'path/to/file'.IO.open: :w, :nl-out("\r\n");.print: "some text";.print-nl; # prints \r\n.close;
(IO::Handle) method printf
Defined as:
multi method printf(IO::Handle: Cool , *)
Formats a string based on the given format and arguments and .print
s the result into the filehandle. See sub sprintf for details on acceptable format directives.
Attempting to call this method when the handle is in binary mode will result in X::IO::BinaryMode
exception being thrown.
my = open 'path/to/file', :w;.printf: "The value is %d\n", 32;.close;
(IO::Handle) method out-buffer
Defined as:
method out-buffer(--> Int) is rw
Controls output buffering and can be set via an argument to open. Takes an int
as the size of the buffer to use (zero is acceptable). Can take a Bool: True
means to use default, implementation-defined buffer size; False
means to disable buffering (equivalent to using 0
as buffer size).
Lastly, can take a Nil
to enable TTY-based buffering control: if the handle is a TTY, the buffering is disabled, otherwise, default, implementation-defined buffer size is used.
See flush to write out data currently in the buffer. Changing buffer size flushes the filehandle.
given 'foo'.IO.open: :w, :1000out-buffer
(IO::Handle) method put
Defined as:
multi method put(** --> True)multi method put(Junction --> True)
Writes the given @text
to the handle, coercing any non-Str objects to Str by calling .Str
method on them, and appending the value of .nl-out
at the end. Junction arguments autothread and the order of printed strings is not guaranteed.
Attempting to call this method when the handle is in binary mode will result in X::IO::BinaryMode
exception being thrown.
my = 'path/to/file'.IO.open: :w;.put: 'some text';.close;
(IO::Handle) method say
Defined as:
multi method say(IO::Handle: ** --> True)
This method is identical to put except that it stringifies its arguments by calling .gist
instead of .Str
.
Attempting to call this method when the handle is in binary mode will result in X::IO::BinaryMode
exception being thrown.
my = open 'path/to/file', :w;.say(Complex.new(3, 4)); # RESULT: «3+4i\n».close;
(IO::Handle) method read
Defined as:
method read(IO::Handle: Int(Cool) = 65536 --> Buf)
Binary reading; reads and returns up to $bytes
bytes from the filehandle. $bytes
defaults to an implementation-specific value (in Rakudo, the value of $*DEFAULT-READ-ELEMS
, which by default is set to 65536
). This method can be called even when the handle is not in binary mode.
(my = 'foo'.IO).spurt: 'I ♥ Perl';given .open
(IO::Handle) method readchars
Defined as:
method readchars(IO::Handle: Int(Cool) = 65536 --> Str)
Reading chars; reads and returns up to $chars
chars (graphemes) from the filehandle. $chars
defaults to an implementation-specific value (in Rakudo, the value of $*DEFAULT-READ-ELEMS
, which by default is set to 65536
). Attempting to call this method when the handle is in binary mode will result in X::IO::BinaryMode
exception being thrown.
(my = 'foo'.IO).spurt: 'I ♥ Perl';given .open
(IO::Handle) method write
Defined as:
method write(IO::Handle: Blob --> True)
Writes $buf
to the filehandle. This method can be called even when the handle is not in binary mode.
(IO::Handle) method seek
Defined as:
method seek(IO::Handle: Int , SeekType --> True)
Move the file pointer (that is, the position at which any subsequent read or write operations will begin) to the byte position specified by $offset
relative to the location specified by $whence
which may be one of:
SeekFromBeginning
: The beginning of the file.
SeekFromCurrent
: The current position in the file.
SeekFromEnd
: The end of the file. Please note that you need to specify a negative offset if you want to position before the end of the file.
(IO::Handle) method tell
Defined as:
method tell(IO::Handle: --> Int)
Return the current position of the file pointer in bytes.
(IO::Handle) method slurp-rest
Defined as:
multi method slurp-rest(IO::Handle: :! --> Buf)multi method slurp-rest(IO::Handle: : --> Str)
DEPRECATION NOTICE: this method is deprecated in the 6.d
version. Do not use it for new code, use .slurp
method instead.
Returns the remaining content of the file from the current file position (which may have been set by previous reads or by seek
.) If the adverb :bin
is provided a Buf will be returned; otherwise the return will be a Str
with the optional encoding :enc
.
(IO::Handle) method slurp
Defined as:
method slurp(IO::Handle: :, :)
Returns all the content from the current file pointer to the end. If the invocant is in binary mode or if $bin
is set to True
, will return a Buf, otherwise will decode the content using invocant's current .encoding
and return a Str.
If :$close
is set to True
, will close the handle when finished reading.
Note: On Rakudo this method was introduced with release 2017.04; $bin
arg was added in 2017.10.
(IO::Handle) method Supply
Defined as:
multi method Supply(IO::Handle: : = 65536)
Returns a Supply
that will emit the contents of the handle in chunks. The chunks will be Buf
if the handle is in binary mode or, if it isn't, Str
decoded using same encoding as IO::Handle.encoding
.
The size of the chunks is determined by the optional :size
named parameter and 65536
bytes in binary mode or 65536
characters in non-binary mode.
"foo".IO.open(:bin).Supply(:size<10>).tap: *.perl.say;# OUTPUT:# Buf[uint8].new(73,32,226,153,165,32,80,101,114,108)# Buf[uint8].new(32,54,33,10)"foo".IO.open.Supply(:size<10>).tap: *.perl.say;# OUTPUT:# "I ♥ Perl"# " 6!\n"
(IO::Handle) method path
Defined as:
method path(IO::Handle:)
For a handle opened on a file this returns the IO::Path that represents the file. For the standard I/O handles $*IN
, $*OUT
, and $*ERR
it returns an IO::Special object.
(IO::Handle) method IO
Defined as:
method IO(IO::Handle:)
Alias for .path
(IO::Handle) method Str
Returns the value of .path
, coerced to Str.
say "foo".IO.open.path; # OUTPUT: «"foo".IO»
(IO::Handle) routine close
Defined as:
method close(IO::Handle: --> Bool)multi sub close(IO::Handle )
Closes an open filehandle. It's not an error to call close
on an already-closed filehandle. Returns True
on success. If you close one of the standard filehandles (by default: $*IN
, $*OUT
, or $*ERR
), that is any handle with native-descriptor 2
or lower, you won't be able to re-open such a handle.
It's a common idiom to use LEAVE
phaser for closing the handles, which ensures the handle is closed regardless of how the block is left.
ifsub do-stuff-with-the-file (IO )my = .open;# stick a `try` on it, since this will get run even when the sub is# called with wrong arguments, in which case the `$fh` will be an `Any`LEAVE try close ;# ... do stuff with the file}given "foo/bar".IO.open(:w)
Note: unlike some other languages, Perl 6 does not use reference counting, and so the filehandles are NOT closed when they go out of scope. While they will get closed when garbage collected, garbage collection isn't guaranteed to get run. This means you must use an explicit close
on handles opened for writing, to avoid data loss, and an explicit close
is recommended on handles opened for reading as well, so that your program does not open too many files at the same time, triggering exceptions on further open
calls.
Note several methods allow for providing :close
argument, to close the handle after the operation invoked by the method completes. As a simpler alternative, the IO::Path type provides many reading and writing methods that let you work with files without dealing with filehandles directly.
(IO::Handle) method flush
Defined as:
method flush(IO::Handle: --> True)
Will flush the handle, writing any of the buffered data. Returns True
on success; otherwise, fails with X::IO::Flush
.
given "foo".IO.open: :w
(IO::Handle) method native-descriptor
Defined as:
method native-descriptor()
This returns a value that the operating system would understand as a "file descriptor" and is suitable for passing to a native function that requires a file descriptor as an argument such as fcntl
or ioctl
.
(IO::Handle) method nl-in
Defined as:
method nl-in(--> Str) is rw
One of the attributes that can be set via .new
or open. Defaults to ["\x0A", "\r\n"]
. Takes either a Str or Array of Str
specifying input line ending(s) for this handle. If .chomp
attribute is set to True
, will strip these endings in routines that chomp
, such as get
and lines
.
with 'test'.IO
(IO::Handle) method nl-out
Defined as:
has Str is rw = "\n";
One of the attributes that can be set via .new
or open. Defaults to "\n"
. Takes a Str specifying output line ending for this handle, to be used by methods .put
and .say
.
with 'test'.IO
(IO::Handle) method opened
Defined as:
method opened(IO::Handle: --> Bool)
Returns True
if the handle is open, False
otherwise.
(IO::Handle) method t
Defined as:
method t(IO::Handle: --> Bool)
Returns True
if the handle is opened to a TTY, False
otherwise.
(IO::Handle) method WRITE
Defined as:
method WRITE(IO::Handle: Blob \data --> Bool)
Called whenever a write operation is performed on the handle. Always receives the data as a Blob, even if a textual writing method has been called.
is IO::Handlemy = IO::Store.new();my = ::OUT;::OUT = ;.say for <one two three>;::OUT = ;say .lines(); # OUTPUT «[one two three]»
In this example we are creating a simple WRITE
redirection which stores anything written to the filehandle to an array. Se need to save the standard output first, which we do in $output
, and then everything that is print
ed or said (through say
) gets stored in the defined IO::Store
class. Two things should be taken into account in this class. By default, IO::Handle
s are in binary mode, so we need to TWEAK
the objects if we want them to work with text. Second, a WRITE
operation should return True
if successful. It will fail if it does not.
(IO::Handle) method READ
Defined as:
method READ(IO::Handle: Int \bytes --> Buf)
Called whenever a read operation is performed on the handle. Receives the number of bytes requested to read. Returns a Buf with those bytes which can be used to either fill the decoder buffer or returned from reading methods directly. The result is allowed to have fewer than the requested number of bytes, including no bytes at all.
If you provide your own .READ
, you very likely need to provide your own .EOF
as well, for all the features to behave correctly.
The compiler may call .EOF
method any number of times during a read operation to ascertain whether a call to .READ
should be made. More bytes than necessary to satisfy a read operation may be requested from .READ
, in which case the extra data may be buffered by the IO::Handle or the decoder it's using, to fulfill any subsequent reading operations, without necessarily having to make another .READ
call.
is IO::Handlemy := IO::Store.new();.print( ) for <one two three>;say .read(3).decode; # OUTPUT «one»say .read(3).decode; # OUTPUT «two»
In this case, we have programmed the two READ
and EOF
methods, as well as WRITE
, which stores every line in an element in an array. The read
method actually calls READ
, returning 3 bytes, which correspond to the three characters in the first two elements. Please note that it's the IO::Handle
base class the one that is taking care of cursor, since READ
just provides a handle into the whole content of the object; the base class will READ
1024 * 1024 bytes at a time. If your object is planned to hold an amount of bytes bigger than that, you will have to handle an internal cursor yourself. That is why in this example we don't actually use the bytes
argument.
(IO::Handle) method EOF
Defined as:
method EOF(IO::Handle: --> Bool)
Indicates whether "end of file" has been reached for the data source of the handle; i.e. no more data can be obtained by calling .READ
method. Note that this is not the same as eof method, which will return True
only if .EOF
returns True
and all the decoder buffers, if any were used by the handle, are also empty. See .READ
for an example implementation.