From: mgarriss@... (mgarriss)
Date: 2003-05-28T21:56:05+09:00
Subject: Re: system calls

This is great and yes, it's worth posting to RAA (after it's
prepared for such a move).  Thank you.

Michael Garriss

Gennady <bystr@mac.com> wrote in message news:<49AA538C-90C7-11D7-AE0C-0003939AEA24@mac.com>...
> Again, I am kind of unsure that it is worth posting to RAA, no good 
> documentation, no formal installation and so on. Meanwhile, I am 
> attaching URL here. If you find it useful, please let me know. Along 
> with it, I am copying a brief description from my first post on the 
> subject:
> 
> http://homepage.mac.com/bystr/Development/Ruby/launch.rb
> 
> ===
> Recently I implemented a facility for such cases and if you are 
> interested I can send it to you (I am not sure it is worth enough to be 
> sent to RAA). It does not spawn threads, all is done with IO#select.
> 
> I called it "launch" and made it available through the Kernel. So in 
> your case it can be used as:
> 
> require 'launch'
> messages = launch "date"
> 
> It returns an array of message arrays, the first element -- messages 
> read from the command's stdout, the second -- from the stderr.
> If the command is killed or returns with error (return code is not 0), 
> exception TerminateError is raised. If you rescue it, you can get the 
> reason for termination (signal or non-zero return) and the return code 
> (signal number if killed). Stderr messages are also available from the 
> exception class.
> 
> In general, it was designed for launching a pipeline of commands with 
> access to all error messages and return codes from all commands in the 
> pipeline. Unfortunately, when you do it with system("command1 | 
> command2 |command3"), you may not even know that command1 or  command2 
> terminated abnormally as shell returns the code of the last command in 
> a pipeline.
> 
> General syntax is:
>    launch [<IO>, ] <command_1> [, <command_2> ... [, <command_N>] { | 
> line_0, line_1, ... line_N | block } -> anArray
>    <IO> - an optional IO object. If specified, the first command's stdin 
> will be redirected from this IO object. Otherwise "/dev/null" is used.
>    <command> - all commands are spawned (fork & exec) with stdout of the 
> previous command redirected to stdin of the next command. Stdout of the 
> last command is read out and messages are stored in the array available 
> as the first element of the returned array. All other elements of the 
> returned array store error messages from stderr's of all commands 
> respectively.
> 
> If a block is specified, lines read from stdout of the last command and 
> stderrs of all command are made available to the block immediately 
> (messages are not stored in the returned array): line_0 (if not nil) is 
> a line from stdout of the last command, line_1 .. line_N (if not nils) 
> are lines read from stderrs of command_1 ... command_N respectively. 
> Only one line passed to the block is not nil.
> 
> I use the block form when I need to show the progress of a long running 
> Unix command (like tar).
> 
> ======
> 
> 
> 
> On Tuesday, May 27, 2003, at 07:44 PM, Pe�a, Botp wrote:
> 
> > Gennady [mailto:bystr@mac.com] wrote:
> >> Recently I implemented a facility for such cases and if you are
> >> interested I can send it to you (I am not sure it is worth
> >> enough to be
> >> sent to RAA). It does not spawn threads, all is done with IO#select.
> >>
> >> I called it "launch" and made it available through the Kernel. So in
> >> your case it can be used as:
> >>
> >> require 'launch'
> >> messages = launch "date"
> >
> > can you post it on raa, pls. It looks useful to me and I'd like to see 
> > the
> > code.
> >
> > kind regards -botp
> >