How to check for command return codes inside a ruby shell script?-CodePudding

I have a simple shell script written in ruby that runs some predefined commands and saves the output strings.

The script works well, but I need a way branch conditionally if the command fails. I've tried using the $? object but the script exits before it gets there.

#!/usr/bin/ruby

def run_command(cmd)
  `#{cmd}`
  if $?.success?
    # continue as normal
  else
    # ignore this command and move on
  end
end

run_command('ls')
run_command('not_a_command')

# Output:
# No such file or directory - not_a_command (Errno::ENOENT)...

I've tried $?.exitstatus or even just puts $? but it always exits before it gets there because the script is obviously running the command before hitting that line.

Is there a way to check if the command will run before actually running it in the script?

Hope that's clear, thanks for your time!

CodePudding user response：

Use system (which returns true or false depending on exit code) instead of backticks (which return output string):

if system(cmd)
  ...
else
  ...
end

If you want it to run quietly without polluting your logs / output:

system(cmd, out: File::NULL, err: File::NULL)