Shell – How send multiple command as input in a program

command lineinputshell

I know how send a command as a input in a program like this:

echo toto | ./my_prog

And with process substitution + redirection:

r < <(echo toto)

But how to do this if I want to input a second or a third input?

For example, I have a program that ask my username first and after this it ask me others informations like a number phone or whatever in different input.

Best Answer

Use { and } to collect the output of multiple programs. For instance, { echo one; echo two; } |program. Leave a space after { and before } and ensure there is a semicolon after the last command within the braces.

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shell – How to Send stdout to Multiple Commands

You can use tee and process substitution for this:

cat file.txt | tee >(pbcopy) | grep errors

This will send all the output of cat file.txt to pbcopy, and you'll only get the result of grep on your console.

You can put multiple processes in the tee part:

cat file.txt | tee >(pbcopy) >(do_stuff) >(do_more_stuff) | grep errors

Sending some input into a process, then resuming input from command line

You can't change what STDIN of telnet is bound to after you start, but you can replace the simple echo with something that will perform more than one action - and let the second action be "copy user input to the target":

{ echo "hello"; cat; } | telnet somewhere 123

You can, naturally, replace cat with anything that will copy from the user and send to telnet.

Keep in mind that this will still be different to just typing into the process. You have attached a pipe to STDIN, rather than a TTY/PTY, so telnet will, for example, be unable to hide a password you type in.

Best Answer

Related Solutions

shell – How to Send stdout to Multiple Commands

Sending some input into a process, then resuming input from command line

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