I want to read user input from STDIN and process the preliminary input while the user is still typing.
A previous answer has some ruby code which enables this behaviour.
How to get a single character without pressing enter?
I would suggest reading something like http://ruby.runpaint.org/io
Call STDIN.getc to get individual characters that the user types.
Related
I am writing a command line code to perform some operations which require a password from the user.I am reading the password from cmd using set/p "pass=>" .
But while using this the password being typed is displayed. I do not want it to be displayed on the cmd window. what modification should i make?
I think CMD does not work in this way. i am guessing you have some sort of a if statement on the inside that will start to run the rest of the program if your input is right. batch files is just a way to get your daily operations faster :)
clsafter "password" typed will prevent people from seeing the password after it was entered.
or maybe this post can help you:
Can I mask an input text in a bat file
I tried running this simple code:
puts 4
i = gets
puts i
It's "working", but the console asks for a string and just then it prints 4 and i
Add a flush call before gets:
$stdout.flush
Instead of explicitly calling $stdout.flush:
$stdout.sync = true
Works in order for me using ruby 1.8.7, 1.9.2 and ree. What version of ruby and operating system are you on?
What are you hoping to accomplish here ?
Normally the interpreter gathers all data before presenting you with the output. It's simply isnt bash :)
I guess you may be hit by output buffering. But your code example does not show how the program might "ask" for input, so I guess that you type answer just before ruby starts. Then your ruby program reads the input from input buffers, as the data is not read directly from the keyboard.
Are you sure that your problem is caused by exactly this code you have shown us?
Usually problems with data shown on terminal in wrong order are caused by using two different output streams: STDIN and STDERR for example. Each stream may decide to flush its data at different times.
if you want to make sure the text is displayed before something happens (as in this example) use the 'flush' command, as Yossi suggests.
In a small Ruby application, I'd like user input to be accepted without having to wait for a carriage return. My understanding is that cbreak mode needs to be enabled in order for the terminal to feed user input directly into the script.
I tried simply running x%[cbreak()] at the top of my script but that didn't work. I've also seen that it's possible to use (n)curses to achieve the same results, although that seems like overkill.
Does anybody have a suggestion on how to implement this?
Thanks
cbreak is a curses function call, so %x definitely doesn't apply (that is for executing shell commands). cbreak is defined in the standard curses library, so that would probably be your best bet.
See:
http://ruby-doc.org/stdlib/libdoc/curses/rdoc/classes/Curses.html#M000280
Edit: you might also check out Curses.getch
One solution which avoids having to use curses (which I find difficult to implement) is to use the shell's read command via %x. It doesn't feel right dipping into the shell to do something that seems like Ruby's STDIN should be responsible for, but it's simple and it works.
#! /usr/bin/ruby
puts "Please enter your first initial"
str = %x[read -s -n1 keypress; echo $keypress]
puts "Your first inital is " + str
I'm trying to determine how the system prints characters to standard input -- that is, how it prints characters which the user can delete and which are considered input if the user hits "Enter."
I happen to be using C, but I would be very surprised if the solution were language-dependent.
Thanks for any insights! : D
As iny says, bash uses readline for its input. The source is available here, and there's a file called complete.c.
To answer your question, I don't think they're actually printed to standard input. Readline contains some kind of buffer for the contents of the line the user is editing, and completion prints into this. When the user presses enter, the contents of the buffer are sent to whatever program wanted to read a line, and in the case of bash, passed along into standard input. (Readline doesn't do this - other programs which use readline might simply store the value into a string for later use.)
Several people have pointed out that bash uses readline, which is true, but I think what you're really asking is how is it able to see what you've typed before you hit enter.
The answer is that ttys (ie: terminals) can be switched into "raw mode", where input processing of the terminal is disabled, and then you'll see every character as it comes in. This also disables automatic echoing of typed characters.
See this guide on Reading a single character from a file or a terminal for more info.
It uses readline library to handle the input and readline provides the history and the completion.
To actually implement completion, access to the keyboard input handling is needed. The completion must be able to modify the buffer used by it. After that it is just about looking at the current input and checking what completions is found. The actual completion logic can work in many ways.
Here's a C snippet that implements tab completion via readline:
http://github.com/rupa/el
In a web interface, I've got a text field. When user enters text and accepts with enter, application performs an action.
I wanted to test the behavior with Selenium. Unfortunately, invoking 'keypress' with chr(13) insert representation of the character into the field.
Is there a way other then submitting the form? I'd like to mimic intended user interaction, without any shortcuts...
This Java code works for me:
selenium.keyDown(id, "\\13");
Notice the escape. You probably need something like chr(\13)
I ended up using selenium.keyPress(id, "\\13");
Though I haven't tested this I imagine you can use "\r\n" appended to a string to simulate a new line. If not look for the languages equivalent to "Environment.NewLine;" ?
It's been a while since I've had to do this, but I seem to recall having to use a javascript snippet to execute the carrage return as opposed to using the Selenium keypress function.
you can use
Webelement.sendkeys(Keys.Enter);