role X::OS

Error reported by the operating system

role X::OS { has $.os-error }

Common role for all exceptions that are triggered by some error reported by the operating system (failed IO, system calls, fork, memory allocation).

Methods

method os-error

method os-error(--> Str:D)

Returns the error as reported by the operating system.

Type Graph

Type relations for X::OS
perl6-type-graph X::OS X::OS Exception Exception X::OS->Exception Mu Mu Any Any Any->Mu Exception->Any X::IO X::IO X::IO->X::OS X::IO->Exception X::IO::Rename X::IO::Rename X::IO::Rename->Exception X::IO::Rename->Exception X::IO::Rename->X::IO X::IO::Symlink X::IO::Symlink X::IO::Symlink->Exception X::IO::Symlink->Exception X::IO::Symlink->X::IO X::IO::Chmod X::IO::Chmod X::IO::Chmod->Exception X::IO::Chmod->Exception X::IO::Chmod->X::IO X::IO::Move X::IO::Move X::IO::Move->Exception X::IO::Move->Exception X::IO::Move->X::IO X::IO::Dir X::IO::Dir X::IO::Dir->Exception X::IO::Dir->Exception X::IO::Dir->X::IO X::IO::Rmdir X::IO::Rmdir X::IO::Rmdir->Exception X::IO::Rmdir->Exception X::IO::Rmdir->X::IO X::IO::DoesNotExist X::IO::DoesNotExist X::IO::DoesNotExist->Exception X::IO::DoesNotExist->Exception X::IO::DoesNotExist->X::IO X::IO::Cwd X::IO::Cwd X::IO::Cwd->Exception X::IO::Cwd->Exception X::IO::Cwd->X::IO X::IO::Chdir X::IO::Chdir X::IO::Chdir->Exception X::IO::Chdir->Exception X::IO::Chdir->X::IO X::IO::Unlink X::IO::Unlink X::IO::Unlink->Exception X::IO::Unlink->Exception X::IO::Unlink->X::IO X::IO::Mkdir X::IO::Mkdir X::IO::Mkdir->Exception X::IO::Mkdir->Exception X::IO::Mkdir->X::IO X::IO::Copy X::IO::Copy X::IO::Copy->Exception X::IO::Copy->Exception X::IO::Copy->X::IO X::IO::Link X::IO::Link X::IO::Link->Exception X::IO::Link->Exception X::IO::Link->Exception X::IO::Link->X::IO

Stand-alone image: vector

Routines supplied by class Exception

X::OS inherits from class Exception, which provides the following routines:

(Exception) method message

Defined as:

method message(Exception:D: --> Str:D)

This is a stub that must be overwritten by subclasses, and should return the exception message.

Special care should be taken that this method does not produce an exception itself.

try die "Something bad happened";
if ($!) {
    say $!.message; # OUTPUT: «Something bad happened.␤» 
}

(Exception) method backtrace

Defined as:

method backtrace(Exception:D: --> Backtrace:D)

Returns the backtrace associated with the exception. Only makes sense on exceptions that have been thrown at least once.

try die "Something bad happened";
if ($!) {
    print $!.backtrace;
}

(Exception) method throw

Defined as:

method throw(Exception:D:)

Throws the exception.

my $exception = X::AdHoc.new;    # Totally fine 
try $exception.throw;            # Throws 
if ($!) { #`( some handling ) }; # Suppress the exception 

(Exception) method resume

Defined as:

method resume(Exception:D:)

Resumes control flow where .throw left it when handled in a CATCH block.

# For example, resume control flow for any exception 
CATCH { default { .resume } }

(Exception) method rethrow

Defined as:

method rethrow(Exception:D:)

Rethrows an exception that has already been thrown at least once. This is different from throw in that it preserves the original backtrace.

my $e = X::AdHoc.new(payload => "Bad situation");
sub f() { die 'Bad' };
sub g() { try f; CATCH { default { .rethrow } } };
g;
CATCH { default { say .backtrace.full } };

(Exception) method fail

Defined as:

multi sub    fail(*@text)
multi sub    fail(Exception $e)
method fail(Exception:D:)

Exits the calling Routine and returns a Failure object wrapping the exception $e - or, for the *@text form, an X::AdHoc exception constructed from the concatenation of @text. If the caller activated fatal exceptions via the pragma use fatal;, the exception is thrown instead of being returned as a Failure.

sub copy-directory-tree ($dir) {
    fail "$dir is not a directory" if !$dir.IO.d;
    ...
}

(Exception) method gist

Defined as:

multi method gist(Exception:D:)

Returns whatever the exception printer should produce for this exception. The default implementation returns message and backtrace separated by a newline.

my $e = X::AdHoc.new(payload => "This exception is pretty bad");
try $e.throw;
if ($!) { say $!.gist; };
# OUTPUT: «This exception is pretty bad 
#   in block <unit> at <unknown file> line 1␤» 

(Exception) sub die

Defined as:

multi sub die()
multi sub die(*@message)
multi sub die(Exception:D $e)
method    die(Exception:D:)

Throws a fatal Exception. The default exception handler prints each element of the list to $*ERR (STDERR).

die "Important reason";

If the subroutine form is called without arguments, the value of $! variable is checked. If it is set to a .DEFINITE value, its value will be used as the Exception to throw if it's of type Exception, otherwise, it will be used as payload of X::AdHoc exception. If $! is not .DEFINITE, X::AdHoc with string "Died" as payload will be thrown.

(Exception) sub warn

Defined as:

multi sub warn(*@message)

Throws a resumable warning exception, which is considered a control exception, and hence is invisible to most normal exception handlers. The outermost control handler will print the warning to $*ERR. After printing the warning, the exception is resumed where it was thrown. To override this behavior, catch the exception in a CONTROL block. A quietly {...} block is the opposite of a try {...} block in that it will suppress any warnings but pass fatal exceptions through.

To simply print to $*ERR, please use note instead. warn should be reserved for use in threatening situations when you don't quite want to throw an exception.

warn "Warning message";