CODEWITHSUNDEEP
linuxbashscriptinginteractive
jovannet
jovannet

Reputation: 53

Bash script without interacting

I would like to do following:

I have a bash script that calls an interactive command that asks the user for a passphrase. I want to specify the passphrase in the script as a variable, and pass that variable to the command non-interactively.

Upvotes: 3

Views: 5891

Answers (4)

ramazan polat
ramazan polat

Reputation: 7910

Lets assume that your script is this(genrsa.sh):

#!/bin/sh 
ssh-keygen -t rsa

Normally, if you execute the genrsa.sh file it will ask for a file name and passphrase twice. Like that:

$./genrsa.sh
Enter file name (/root/.ssh/id_rsa):
Enter passphrase(empty for no passphrase:mypassword
Enter same passphrase:mypassword
public key generated, bla bla bla...
$

You want to change the script in a way so you can pass your passphrase as a parameter. So it won't wait for you to type. You will use it like that:

$./genrsa.sh mypassword

To do that, you have to change your script to something like that(genrsa2.sh):

#!/bin/sh   
passphrase=$1
set timeout 2
ssh-keygen -t rsa
expect \"Enter file\" { send \"\r\" }            
expect \"empty for\" { send \"$passphrase\r\" }
expect \"same passphrase\" { send \"$passphrase\r\" }

Upvotes: 1

Jack
Jack

Reputation: 1525

Here is a very basic technique. Provide an input file to the script. It is a good choice if you don't want to modify the script itself.

I have to use an example that I dreamed up myself. Here's a basic script prompting the user for values, call it scp:

#!/bin/bash

echo -n "Type something: "
read X
echo You gave: $X

echo -n "Type something again: "
read Z
echo This time gave: $Z

You can provide an input file as such, call it input:

value for X
value for Z

Then to invoke the script providing input for input to the script do this:

cat input | ./scp

..or alternatively and concisely:

./scp < input

The output looks like this:

Type something: You gave: value for X
Type something again: This time gave: value for Z

Upvotes: 1

ramonovski
ramonovski

Reputation: 414

${2:-defaultvalue}

Where 2 (could be the 1st parameter too) is the second positional parameter and "defaultvalue" is the value the variable takes in case you don't specify any value.

Upvotes: -2

hexparrot
hexparrot

Reputation: 3437

I believe you would like to look into expect. This utility is designed specifically for typing on behalf of the user.

Assuming your script has a prompt (or a line that dependably appears before user interaction is required), expect can parse the output, and when it sees the line, e.g., 'passphrase:', enter your passphrase and continue execution of the script.

Upvotes: 4

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