W3cubDocs

/Crystal 0.31

enum Signal

Overview

Safely handle inter-process signals on POSIX systems.

Signals are dispatched to the event loop and later processed in a dedicated fiber. Some received signals may never be processed when the program terminates.

puts "Ctrl+C still has the OS default action (stops the program)"
sleep 3

Signal::INT.trap do
  puts "Gotcha!"
end
puts "Ctrl+C will be caught from now on"
sleep 3

Signal::INT.reset
puts "Ctrl+C is back to the OS default action"
sleep 3

Note:

  • An uncaught exception in a signal handler is a fatal error.

Defined in:

signal.cr

Enum Members

HUP = 1
INT = 2
QUIT = 3
ILL = 4
TRAP = 5
IOT = 6
ABRT = 6
FPE = 8
KILL = 9
BUS = 7
SEGV = 11
SYS = 31
PIPE = 13
ALRM = 14
TERM = 15
URG = 23
STOP = 19
TSTP = 20
CONT = 18
CHLD = 17
TTIN = 21
TTOU = 22
IO = 29
XCPU = 24
XFSZ = 25
VTALRM = 26
USR1 = 10
USR2 = 12
WINCH = 28
PWR = 30
STKFLT = 16
UNUSED = 31

Instance Method Summary

Instance methods inherited from struct Enum

&(other : self) &, +(other : Int) +, -(other : Int) -, <=>(other : self) <=>, ==(other : self) ==, ^(other : self) ^, clone clone, each(&block) each, hash(hasher) hash, includes?(other : self) includes?, to_f32 : Float32 to_f32, to_f32! : Float32 to_f32!, to_f64 : Float64 to_f64, to_f64! : Float64 to_f64!, to_i : Int32 to_i, to_i16 : Int16 to_i16, to_i16! : Int16 to_i16!, to_i32 : Int32 to_i32, to_i32! : Int32 to_i32!, to_i64 : Int64 to_i64, to_i64! : Int64 to_i64!, to_i8 : Int8 to_i8, to_i8! : Int8 to_i8!, to_json(json : JSON::Builder) to_json, to_s(io : IO) : Nil
to_s : String to_s
, to_u16 : UInt16 to_u16, to_u16! : UInt16 to_u16!, to_u32 : UInt32 to_u32, to_u32! : UInt32 to_u32!, to_u64 : UInt64 to_u64, to_u64! : UInt64 to_u64!, to_u8 : UInt8 to_u8, to_u8! : UInt8 to_u8!, to_yaml(yaml : YAML::Nodes::Builder) to_yaml, |(other : self) |, ~ ~

Constructor methods inherited from struct Enum

from_value(value : Int) : self from_value, from_value?(value : Int) : self? from_value?, new(ctx : YAML::ParseContext, node : YAML::Nodes::Node)
new(pull : JSON::PullParser) new
, parse(string : String) : self parse, parse?(string : String) : self? parse?

Class methods inherited from struct Enum

each(&block) each, names : Array(String) names, values : Array(self) values

Instance methods inherited from module Comparable(Enum)

<, <=(other : T) <=, <=>(other : T) <=>, ==(other : T) ==, >(other : T) >, >=(other : T) >=

Instance methods inherited from struct Value

==(other : JSON::Any)
==(other : YAML::Any)
==(other) ==
, dup dup

Instance methods inherited from class Object

!=(other) !=, !~(other) !~, ==(other) ==, ===(other : JSON::Any)
===(other : YAML::Any)
===(other) ===
, =~(other) =~, class class, dup dup, hash(hasher)
hash hash
, inspect(io : IO) : Nil
inspect : String inspect
, itself itself, not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, tap(&block) tap, to_json(io : IO)
to_json to_json
, to_pretty_json(indent : String = " ")
to_pretty_json(io : IO, indent : String = " ") to_pretty_json
, to_s : String
to_s(io : IO) : Nil to_s
, to_yaml(io : IO)
to_yaml to_yaml
, try(&block) try, unsafe_as(type : T.class) forall T unsafe_as

Constructor methods inherited from class Object

from_json(string_or_io, root : String) : self
from_json(string_or_io) : self from_json
, from_yaml(string_or_io : String | IO) : self from_yaml

Instance Method Detail

def abrt?Source

def alrm?Source

def bus?Source

def chld?Source

def cont?Source

def fpe?Source

def hup?Source

def ignore : NilSource

Clears the handler for this signal and prevents the OS default action.

Note that trying to ignore CHLD will actually set the default crystal handler that monitors and reaps child processes. This prevents zombie processes and is required by Process#wait for example.

def ill?Source

def int?Source

def io?Source

def iot?Source

def kill?Source

def pipe?Source

def pwr?Source

def quit?Source

def reset : NilSource

Resets the handler for this signal to the OS default.

Note that trying to reset CHLD will actually set the default crystal handler that monitors and reaps child processes. This prevents zombie processes and is required by Process#wait for example.

def segv?Source

def stkflt?Source

def stop?Source

def sys?Source

def term?Source

def trap(&handler : Signal -> ) : NilSource

Sets the handler for this signal to the passed function.

After executing this, whenever the current process receives the corresponding signal, the passed function will be called (instead of the OS default). The handler will run in a signal-safe fiber thought the event loop; there is no limit to what functions can be called, unlike raw signals that run on the sigaltstack.

Note that CHLD is always trapped and child processes will always be reaped before the custom handler is called, hence a custom CHLD handler must check child processes using Process.exists?. Trying to use waitpid with a zero or negative value won't work.

def trap?Source

def tstp?Source

def ttin?Source

def ttou?Source

def unused?Source

def urg?Source

def usr1?Source

def usr2?Source

def vtalrm?Source

def winch?Source

def xcpu?Source

def xfsz?Source

© 2012–2019 Manas Technology Solutions.
Licensed under the Apache License, Version 2.0.
https://crystal-lang.org/api/0.31.1/Signal.html