Is there some way to run a (shell) command from Ruby displaying but also capturing the output? Maybe with the help of some gem?
What I mean by displaying is not printing it at the end, but as it appears, so the user gets the feedback of what's going on when running slow commands.
You can run system call like this:
`sleep --help`
Or like this
system "sleep --help"
Or
%x{ sleep --help }
In case of system it will print output and return true or nil, other two methods will return output
PS Oh. It is about displaying in real time.
So. You could use something like this:
system("ruby", "-e 100.times{|i| p i; sleep 1}", out: $stdout, err: :out)
To print data in realtime and store it in variable:
output = []
r, io = IO.pipe
fork do
system("ruby", "-e 3.times{|i| p i; sleep 1}", out: io, err: :out)
end
io.close
r.each_line{|l| puts l; output << l.chomp}
#=> 0
#=> 1
#=> 2
p output
#=> ['0', '1', '2']
Or use popen
output = []
IO.popen("ruby -e '3.times{|i| p i; sleep 1}'").each do |line|
p line.chomp
output << line.chomp
end
#=> '0'
#=> '1'
#=> '2'
p output
#=> ['0', '1', '2']
system that takes out and err parameters? Is this Ruby 2.0?
I used open3 to captured the output of executed shell command from ruby code.
require 'open3'
stdout, stdeerr, status = Open3.capture3("ls")
puts stdout
You can redirect the output
system 'uptime > results.log'
or save the results.
result = `uptime`
result = %x[uptime]
see here. Getting progress information or output in realtime is more complicated, I doubt that there is a simple solution. Maybe it is possible with advanced process management functions such as Open3.popen3. You could also try to use a pseudo terminal with pty and grap the output there.
puts result . This will display the result in console.If you are willing to explore a solution outside the standard library, you may also use Mixlib::ShellOut to both stream output and capture it:
require 'mixlib/shellout'
cmd = 'while true; do date; sleep 2; done'
so = Mixlib::ShellOut.new(cmd)
so.live_stream = $stdout
so.run_command
out = so.stdout
Have a look at the Ruby docs for the non-blocking form of Open3.popen3:
https://ruby-doc.org/stdlib-3.1.2/libdoc/open3/rdoc/Open3.html#method-c-popen3
Although the name "popen3" is not as familiar as the "system()" command, it is currently the recommended method for running system commands from Ruby with several advantages over the system() command. There are several variations in the Open3 class: capture*, pipline*, popen*.
The docs are quite clear, so I won't repeat them here.
