Bug #10362: spawn doesn't raise exception on redirection error

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 2.0.0p247 (2013-06-27) [i386-mingw32]
• Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN

[bdimych (Dmitry Bolshakov)]

irb(main):002:0*
irb(main):003:0*
irb(main):004:0* system 'cmd', '/c', 'echo', 'aaa'
aaa
=> true
irb(main):005:0>
irb(main):006:0*
irb(main):007:0*
irb(main):008:0* system 'cmd', '/c', 'echo', 'aaa', :out => ['bad/file.txt', 'w']
=> nil
irb(main):009:0>
irb(main):010:0*
irb(main):011:0*
irb(main):012:0*
irb(main):013:0* system 'cmd', '/c', 'echo', 'aaa', :out => File.open('bad/file.txt', 'w')
Errno::ENOENT: No such file or directory - bad/file.txt
        from (irb):13:in `initialize'
        from (irb):13:in `open'
        from (irb):13
        from C:/Ruby200/bin/irb:12:in `<main>'
irb(main):014:0>
irb(main):015:0*
irb(main):016:0*

exception is much more descriptive than just nil

[normalperson (Eric Wong)]

[e-mail] wrote:

irb(main):013:0* system 'cmd', '/c', 'echo', 'aaa', :out => File.open('bad/file.txt', 'w')
Errno::ENOENT: No such file or directory - bad/file.txt
from (irb):13:in initialize' from (irb):13:in open'
from (irb):13
from C:/Ruby200/bin/irb:12:in `'

exception is much more descriptive than just nil

Right, but I think the system' method is intended to hide errors by default. $? must be checked when system' returns nil:

if system('non-existent-command').nil?
  $? => #<Process::Status: pid ... exit 127>
end

I think it is in the spec for `system' to behave like this.

[nobu (Nobuyoshi Nakada)]

Yes, it's intentional spec, but to raise errors Process.spawn and Process.wait are needed.
It may be good to add an option for errors to system.

[normalperson (Eric Wong)]

On the other hand, maybe we should allow Ruby-level options to `system'
to raise, but continue hiding errors when running the command itself.

In other words:

# continue old 1.8 behavior if redirect is done via shell
# (n.b. this example is bad practice, but just an example)
system('true >bad/file.txt') -> nil

So I think the original example by Dmitry should raise:

system('true', out: %w(bad/file.txt w)) -> Errno...

Maybe this (potentially incompatible) change can be acceptable
for 2.2 (if not, then for Ruby 3.0)

[jeremyevans0 (Jeremy Evans)]

• Status changed from Open to Closed

system was made more strict for redirection errors between Ruby 2.2 and 2.3:

speedstar$ ruby22 -e "p system('true', out: %w(bad/file.txt w))"
nil

speedstar$ ruby23 -e "p system('true', out: %w(bad/file.txt w))" 
-e:1:in `system': No such file or directory - bad/file.txt (Errno::ENOENT)
        from -e:1:in `<main>'