How can I continuously output the results of a long running shell command, as the output becomes available?
Currently I need to do this (which I can only see after command has finished)
puts
long_running_shell_command
What I want to do conceptually is
puts_immediately
long_running_shell_command
Redirect the output to STDOUT:
# waits a second, prints the current directory's contents, waits 5 seconds
system('sleep 1; ls; sleep 5', out: STDOUT)
My favorite way to work with shell commands is like so:
Open3.popen3 "shellcommand --args --more-args" do |stdin, stdout, stderr, thread|
while line = stdout.gets
puts line
end
end
The command gives you input, output and error streams. You can call stdout.gets to get the next line of output (my favorite), or stdout.getc for the next character, if you really want immediacy. The function waits until input is available and then returns nil when the command completes, so a common technique is to wrap the command in a while-loop and have a set of commands repeatedly execute until the command completes.
