Problem executing bash script from ruby

I have little experience with this sort of thing, but it looked fairly
straightforward. I’m in trouble, however.


From /home/tomc/Ruby-work/setnet/bin/ I launch “./setnet”. This dir
contains: setnet

“./setnet” contains these lines (among others), and works fine:

manager =

The “SN.rb” module is in “/home/tomc/Ruby-work/setnet/lib/setnet”, and
contains a method with this code snippet -

puts “\n=== generating new rdocs for SetNet ===”
system(“ls”) # to verify where I am in the filesystem
if $? != 0
puts “*** command failed: status = #{$?.exitstatus}”

This snippet executes by means of selection from a menu, with this
result -

=== generating new rdocs for SetNet === setnet
*** command failed: status = 127 contains:

cd …/lib/setnet
echo “dir–”
echo “rdoc executing --”
rdoc -N -x ./doc

What I’m trying to do is acquire the functionality of generating new
rdocs for my program without having to manually go back to a command
line. Every attempt I made to make a single “system()” call from within
ruby, to generate the rdocs, have failed. In my experience, rdoc is
excessively quirky. I’ve spent most of today trying to get it to do some
simple things, and failing, even though I’ve very carefully following
the documentation. I do have something that works - that “rdoc -N -s
./doc” command, but only when it’s executed from within the right dir.

Since -

  • I’m allowed one command per “system()” call, and
  • upon return from that call, the present working dir is reset to its
    prior state…

my only option appears to be to issue the commands I’d use in a manual
interaction with the CLI from within a script file, and that’s what I’m
trying to do.

My questions:

  1. Is there some obvious reason by my attempt to execute is
  2. How can I make use of the process status output I’ve captured? I’ve
    searched Pickax 3rd ed., and with Google, and I’m not receiving much
    enlightenment. What do the “big boys/girls” do with this status output?

Thanks very much for any help anyone can offer.


Tom C., MS MA, LMHC - Private practice Psychotherapist
Bellingham, Washington, U.S.A: (360) 920-1226
<< [email protected] >> (email)
<< >> (website)
<< >> (mental health weblog)

An option would be to run the bash script inside a PTY… but that makes
simply to complex for something that could all be done from within
you try calling rdoc straight from ruby instead of bash?

2009/7/15 Tom C. [email protected]

  1. I googled: exist status 127 - here’s the response:
    If a command is not found, the child process created to execute it
    returns a status of 127.

I think you should try specifying the absolute path of the shell script.

  1. If you want to capture the output of your command, you should use the
    %x{} notation or the `` notation.

c = %x{pwd}
is equivalent to:
c = pwd

the system command differs from these in that it output the results to
stdout and any assignments just contain true or false depending on the
exit status. That would be useful if you wanted to run a script and
cared only about whether the script was successful or not.

a = system(“pwd”)
puts a

check out:

Here’s another example summarizing what I’ve described here. You’d
probably do well to open irb and type the commands out individually.

lukebook:~ lukec$ irb
irb(main):001:0> a = pwd
=> “/Users/lukec\n”
irb(main):002:0> puts a
=> nil
irb(main):003:0> a.upcase


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