Respond to Prompt in Bash Script
I work on a project that requires I frequently build and destroy a virtual machine. I don't enjoy having to do so but virtual machines can be notoriously difficult to prop up, especially when you have a complex app living within it.
Manually typing the same commands over and over can be mind-numbing so I've create a bash script to handle all of the work for me. One hiccup to the process is needing to confirm removal of an existing virtual machine; using a pipe and echo allows me to answer the prompt:
# ... some directives here
# Remove the machine, confirming "y" when asked by docker-machine
echo 'y' | docker-machine rm default
# ... more directives here
Using echo I pipe a y response to docker-machine's confirmation prompt, thus allowing the script to move forward with other tasks without the need for manual intervention.
I don't, however, know how to handle multiple prompts -- can you tell me and everyone else?
![Chris Coyier’s Favorite CodePen Demos]()
David asked me if I'd be up for a guest post picking out some of my favorite Pens from CodePen. A daunting task! There are so many! I managed to pick a few though that have blown me away over the past few months. If you...
![9 Mind-Blowing Canvas Demos]()
The <canvas> element has been a revelation for the visual experts among our ranks. Canvas provides the means for incredible and efficient animations with the added bonus of no Flash; these developers can flash their awesome JavaScript skills instead. Here are nine unbelievable canvas demos that...
![Google-Style Element Fading Using MooTools or jQuery]()
Google recently introduced an interesting effect to their homepage: the top left and top right navigation items don't display until you move your mouse or leave the search term box. Why? I can only speculate that they want their homepage as...
![CSS Columns]()
One major gripe that we've always had about CSS is that creating layouts seems to be more difficult than it should be. We have, of course, adapted and mastered the techniques for creating layouts, but there's no shaking the feeling that there should be a...
As far as I know this is usually done with the yes command:
This should also respond to multiple prompts.
Ah yes, I did experiment with that. But what if I know the multiple prompt responses should be “y”, “n”, “3”? That would be useful.
To expand on what Andreas said, you can build a canned file of responses, one per line (extra blanks for the equivalent of hitting enter) and sending that to your program:
Can’t you stream a file in? Like in
Try a here string.
while IFS= read -r; do echo "E- $REPLY" done <<<"y n 3"Will print the three lines of responses. Assuming the docker prompt is similar to read it should work.
The ‘expect’ utility can be installed on most Linux boxes.
https://en.wikipedia.org/wiki/Expect
I agree about ‘expect’ as Rohit mentions, it’s usually what you resort to when piping doesn’t work for different reasons (such as passwords being read from physical terminal only, input being prematurely consumed by a loop, etc).
The tool is {advanced|complicated} enough to maybe warrant a future post ;-)
In my team we use Vagrant and Ansible to do these kinds of things. They are very helpful tool for popping up a dev env with customized apps / configs.
I have not tried Ansible for Docker but there is a page for it https://www.ansible.com/docker