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?
![Detect DOM Node Insertions with JavaScript and CSS Animations]()
I work with an awesome cast of developers at Mozilla, and one of them in Daniel Buchner. Daniel's shared with me an awesome strategy for detecting when nodes have been injected into a parent node without using the deprecated DOM Events API.
![LightFace: Facebook Lightbox for MooTools]()
One of the web components I've always loved has been Facebook's modal dialog. This "lightbox" isn't like others: no dark overlay, no obnoxious animating to size, and it doesn't try to do "too much." With Facebook's dialog in mind, I've created LightFace: a Facebook lightbox...
![Drag and Drop MooTools File Uploads]()
Honesty hour confession: file uploading within the web browser sucks. It just does. Like the ugly SELECT element, the file input is almost unstylable and looks different on different platforms. Add to those criticism the fact that we're all used to drag and drop operations...
![Hot Effect: MooTools Drag Opacity]()
As you should already know, the best visual features of a website are usually held within the most subtle of details. One simple trick that usually makes a big different is the use of opacity and fading. Another awesome MooTools functionality is...
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