How to capture the output of a command without it displaying in stdout

Question

How can I capture the output of a command and check for what it says without the command displaying in stdout? For example:

  def update!
      `git pull origin master`
      if $?.exitstatus > 0
        puts 'Failed to update'
      elsif $?.success?
        puts 'Upgraded successfully'
      else
        puts 'Already up to date'
      end
    end

How can I capture the output of this in order to check whether the command says up-to date, an error occurs, or successfully updates? Is there a way to write the output to a file instead of to the console?

Update for answer:

def update!
  update_status = `git pull origin master 2>&1`
  if $?.exitstatus > 0
    puts 'error'
  elsif update_status =~ /Already up-to date/
    puts 'same version as origin master'
  else
    puts 'updated'
  end
end

The output for this will always be:

[06:44:29 INFO] Updating to newest version..
updated

Even if the version is the same as the origin. What I would like to do, if possible, is save the stdout of the command to a file and read from that file to discover if the program was updated or not. I think that would be the easiest way to go about doing this.

@sagarpandya82 No, I'm trying to get a update method for a program I have written and want to capture the output of git itself. I just don't know if it's possible to write the output to a file or not — User9123, Dec 22 '16 at 01:57

akuhn · Accepted Answer · 2016-12-22T02:17:13.100

1

You can assign the output of the command to a string.

Use 2>&1 to redirect stderr to stdout and thus capture all the output.

str = `git pull origin master 2>&1`
if $?.exitstatus > 0
  ...
elsif str =~ /up-to-date/
  ...
else
  ...
end

edited Dec 22 '16 at 02:17

answered Dec 22 '16 at 01:54

akuhn

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This won't work, when `git` is already up to date it will exit with a status of 0, so the `else` is useless – User9123 Dec 22 '16 at 01:56
I would need to somehow capture the information and check if it says either `updating`, `up-to date`, or some kind of error – User9123 Dec 22 '16 at 01:58
Gotcha, updating! – akuhn Dec 22 '16 at 01:59
Thank you! Much appreciated – User9123 Dec 22 '16 at 02:01
This will still output the command `* branch master -> FETCH_HEAD ` I'm trying to prevent that from showing – User9123 Dec 22 '16 at 02:15
What's that do..? – User9123 Dec 22 '16 at 02:24
It redirects stderr to stdout, see comment in my post. – akuhn Dec 22 '16 at 02:26
That's awesome, however this doesn't work as you'd think it would, see my update – User9123 Dec 22 '16 at 12:45

How to capture the output of a command without it displaying in stdout

1 Answers1