What I would like to do is:
run a ruby script...
that executes a shell command
and redirects it to a named pipe accessible outside the script
from the system shell, read from that pipe
That is, have the Ruby script capture some command output and redirect it in such a way that it's connectable to from outside the script?
I want to mention that the script cannot simply start and exit, since it's a REPL. The idea is that using the REPL you would be able to run a command and redirect its output elsewhere to consume it.
Using abort and an exit message, will pass the message to STDERR (and the script will fail with exit code 1). You can pass this shell command output in this way.
This is possibly not the only (or best) way, but it has worked for me in the past.
[edit]
You can also redirect the output to a file (using standard methods), and read that file outside the ruby script.
require 'open3'
stdin, stderr, status = Open3.capture3(commandline)
stdin.chomp #Here, you should ge
Incase, if someone wanted to use you can get the output via stdin.chomp
Related
If I have this batch:
ScriptA.bat
someprog.exe
And this one:
ScriptB.bat
CALL ScriptA.bat
And I execute a command like:
ScriptB.bat > test.log
The output from someprog.exe is not logged. It flows through to the console. How can I avoid having to explicitly pipe the output of someprog.exe to a file, and instead just capture that from a higher level?
(Note I ultimately want to do this with a great many scripts launching assorted exes from inside those nesting, and I can't edit them all to redirect the output of each and every sub process they invoke).
I found the answer to this on another SO thread:
https://stackoverflow.com/a/11955380/3220983
As you'll see if reading the comments under the question, the problem I was encountering was that the messages I couldn't capture were not being piped to stdout or stderr at all! They were going straight to the console via something akin to a CON redirect from inside the specific executable I was trying to use.
The link I posted shows how to launch a PowerShell script from a batch script, which captures the entire console window contents, inclusive of CON output!
I am designing a ruby program that needs to run a command and store it a variable.
var = exec('some command');
This doesn't work the way I want it to, it just prints the output from the command prompt and then ends the program.
So is there a function that doesn't end the program, doesn't print the cmd output and stores the information in a variable?
Thanks in advance.
You need to use either Ruby's built in backtick syntax, or use %x
output = `some command`
or
output = %x(some "command")
Open3 grants you access to stdin, stdout, stderr and a thread to wait
the child process when running another program. You can specify
various attributes, redirections, current directory, etc., of the
program as Process.spawn.
See the various ways of executing a command
I want to run an executable from a ruby rake script, say foo.exe
I want the STDOUT and STDERR outputs from foo.exe to be written directly to the console I'm running the rake task from.
When the process completes, I want to capture the exit code into a variable. How do I achieve this?
I've been playing with backticks, process.spawn, system but I cant get all the behaviour I want, only parts
Update: I'm on Windows, in a standard command prompt, not cygwin
system gets the STDOUT behaviour you want. It also returns true for a zero exit code which can be useful.
$? is populated with information about the last system call so you can check that for the exit status:
system 'foo.exe'
$?.exitstatus
I've used a combination of these things in Runner.execute_command for an example.
backticks will get stdout captured into resulting string
foo.exe suggests you are running windows - do you have anything like cygwin installed? if you run your script within unixy shell you can do this:
result = `foo.exe 2>&1`
status = $?.exitstatus
quick googling says this should also work in native windows shell but i can't test this assupmtion
I'm trying this in ruby.
I have a shell script to which I can pass a command which will be executed by the shell after some initial environment variables have been set. So in ruby code I'm doing this..
# ruby code
my_results = `some_script -allow username -cmd "perform_action"`
The issue is that since the script "some_script" runs "perform_action" in it's own environment, I'm not seeing the result when i output the variable "my_results". So a ruby puts of "my_results" just gives me some initial comments before the script processes the command "perform_action".
Any clues how I can get the output of perform_action into "my_results"?
Thanks.
The backticks will only capture stdout. If you are redirecting stdout, or writing to any other handle (like stderr), it will not show up in its output; otherwise, it should. Whether something goes into stdout or not is not dependent on an environment, only on redirection or direct writing to a different handle.
Try to see whether your script actually prints to stdout from shell:
$ some_script -allow username -cmd "perform_action" > just_stdout.log
$ cat just_stdout.log
In any case, this is not a Ruby question. (Or at least it isn't if I understood you correctly.) You would get the same answer for any language.
I have a program that I want to automate runs for, since it takes awhile to complete. For some reason it outputs everything to stderr instead of stdout, and I'd like to check on its progress, so I find myself needing to redirect stderr output within a start command.
I tried this:
start "My_Program" "C:\Users\Me\my_program.exe" --some --presets --for --my_program.exe --output "C:\Users\Me\output_file_for_my_program" "C:\Users\Me\input_file_for_my_program" 2>"C:\Users\Me\my_program_output.log"
But it turns out that the redirect is being picked up by start, so that I get a 0-byte file with the result of "start" - namely, nothing. Is there any way to make the output redirection attach in some way to the output of my_program?
I've experimented with escaping, and neither "^2>" nor "2^>" seem to work.
If "Workaround Oriented Programmming" is acceptable (it probably is, you are programming Windows Batch lol), you could put the problematic code line in another .BAT file, without any "start" and then "start" this other BAT.