From: Robert Klemme <shortcutter@...>
Date: 2010-06-21T18:02:20+09:00
Subject: Re: How to print exit status to a log file?

Please don't top post.

2010/6/21 Martin Hansen <mail@maasha.dk>:
> I would like to print the exit status from within the current Ruby
> script to a log file. I have been messing a bit with $?, but that way I
> get "pid 8144 exit 0" in the log file and "Interrupted" goes to terminal
> - I wanted "Interrupted" in the log file.

"Interrupted" is not an exit status.  This is most likely written by
the other process that you started.  You either need to catch the
other process's output (most likely stderr) or invent a mechanism to
report the interruption via the exit status (this works only if you
have control over the other process's code).  Then you can interpret
the exit status to write your log message.

irb(main):008:0> system "true"
=> true
irb(main):009:0> $?
=> #<Process::Status: pid 712 exit 0>
irb(main):010:0> $?.exitstatus
=> 0

If you want to catch the output you can use one of the popen methods, e.g.

irb(main):001:0> require 'open3'
=> true
irb(main):002:0> Open3.popen3 "ls", "nonexistent" do |si,so,serr,th|
irb(main):003:1* p serr.read
irb(main):004:1> st = th.value
irb(main):005:1> p st, st.exitstatus
irb(main):006:1> end
"ls: cannot access nonexistent: No such file or directory\n"
#<Process::Status: pid 3160 exit 2>
2
=> [#<Process::Status: pid 3160 exit 2>, 2]

> I have not been able to make
> trap() do the trick, and with trap I loose the default exit and stack
> trace output (I think trap is to be avoided).

trap in your Ruby script will trap signals for this process not the
forked process - unless you use the block form of fork in which case I
believe the child inherits all signal handlers.

Kind regards

robert

-- 
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