trap(:INT); system(); STDIN.gets(); ^C

Ruby
1

Considering a trivial example:

trap :INT do
puts
puts ‘Bye’
exit
end

system ‘date’

print 'Say something: ’
STDOUT.flush
puts “You said: #{STDIN.gets}”

When prompted to say something, hitting Ctrl+C will call trap(:INT)
block.
However, after uncommenting line 7, Ctrl+C won’t cause a call to
trap(:INT) block unless I send a newline or EOF.
Can anyone shed some light on this one?

Platform: linux; ruby 1.8.7

Thanks

2

unknown wrote:

With or without line 7, here both programs behave the same (Ctrl-C +
EOF -> Bye):

So you need to hit ^C^D every time?

Here’s the behavior I’m getting:

without system(‘date’)

$ ruby test.rb
Say something: ^C
Bye

with system(‘date’)

$ ruby test.rb
Wed Mar 31 20:04:28 EEST 2010
Say something: ^C

3

Might be worth to mention that both of the alternatives below will
immediately exit after ^C

ALT 1

trap :INT do
puts
puts ‘Bye’
exit
end

puts IO.popen(‘date’).gets
print 'Say something: ’
STDOUT.flush
puts “You said: #{STDIN.gets}”

ALT 2

begin
system ‘date’
print 'Say something: ’
STDOUT.flush
puts “You said: #{STDIN.gets}”
rescue Interrupt
puts
puts ‘Bye’
exit
end

4

On Wed, Mar 31, 2010 at 2:47 PM, Tudor L. [email protected]
wrote:

When prompted to say something, hitting Ctrl+C will call trap(:INT)
block.
However, after uncommenting line 7, Ctrl+C won’t cause a call to
trap(:INT) block unless I send a newline or EOF.

With or without line 7, here both programs behave the same (Ctrl-C +
EOF → Bye):

$ ruby a.rb
Say something:
Bye
$ ruby b.rb
Wed Mar 31 15:43:32 EDT 2010
Say something:
Bye

Platform: linux; ruby 1.8.7

$ uname -a
Linux mcu.claw.ctc.com 2.6.18-164.11.1.el5 #1 SMP Wed Jan 20 07:39:04
EST 2010 i686 i686 i386 GNU/Linux
$ ruby -v
ruby 1.8.5 (2006-08-25) [i386-linux]

5

On Wed, Mar 31, 2010 at 3:43 PM, Tudor L. [email protected]
wrote:

unknown wrote:

With or without line 7, here both programs behave the same (Ctrl-C +
EOF → Bye):

So you need to hit ^C^D every time?

yes, on this host both versions act like