Running a command from Ruby displaying and capturing the output

Question

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.

Answer 1

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'] 

Answer 2

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.