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I have an interactive application that takes input from the keyboard.

Whenever I run the application I always write the same things in the beginning. So I was thinking I could make a file with those things and redirect them to the application with:

myapplication < myinput.txt

The problem is that when I am done with that I want to give control back to the keyboard so I can type the rest of the input. Is it possible? I don't mind using a bash script.

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Your app must handle that. After program start, when it hits EOF on fd 0, it should close it and open /dev/tty for reading. Then you can start consuming lines from the keyboard. –  ott-- Dec 26 '12 at 16:24
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1 Answer

up vote 3 down vote accepted

I'm not sure about that one, but if the command you want to use is a simple non-interactive one, and you just want to types things into it (and prepend those with the content of 'myinput.txt', try:

cat myinput.txt - | command


cat myinput.txt - | grep something

But if you need more complicated interaction, you should probably use expect (which is not trivial to use at first, but very powerful).

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Thanks. However I want firstly the myinput.txt to be sent to the command and after that be able and type things. –  Pithikos Dec 26 '12 at 16:06
The command I show above will : first output content of "myinput.txt" and then output content of "-" (which, here, for cat, means the standard input, ie what you'll type next). Try if it works, but as I said, it's limited and not very friendly (especially if the command you type into is something like a visual editor, etc). ex: cat myinput.txt - | ssh user@host works more or less. Finish by typing "exit" and return, and it should exit the ssh... (put : ls -al followed by a return, in myinput.txt, for example) –  Olivier Dulac Dec 26 '12 at 16:23
You're right. It actually works. Thanks a dozen :) –  Pithikos Dec 26 '12 at 16:42
Enjoy :) (and note that the '-' notation is used in many unix utilities, for example tar, grep, etc., and is usefull for many things) –  Olivier Dulac Dec 27 '12 at 11:11
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