How to pass input to a script from terminal?

Question

I have a python script that expects user input like this:

Instead of executing the program and inputting "John" I want to pass the input to it from the command line like $ python script.py < "John" but it doesn't work. Is there a way to achieve what I want?

Answer 1

If the script uses its stdin to read data, this line you used

python script.py < "John"

should work, except it tries to send the content of a file named John to the stdin of the script (and it will fail if there's no such file; I guess this happened to you). In Bash there's a way to send a string though, here string:

python script.py <<< "John"

A newline is appended automatically. Another way is with a pipeline:

printf '%s\n' "John" | python script.py

and this should work even in plain sh. So should this:

echo "John" | python script.py

Note printf is in general better than echo, but with this fixed string both commands should work right.

---

Neither of the above will work if the script directly uses its controlling terminal (/dev/tty) instead of its stdin to read user's response. If so, expect (like in this other answer) will be useful. You didn't show us the script itself so it's impossible to tell for sure; you should know.

Answer 2

A really simple way to achieve this is to use sys.argv from the sys module, which allows you to access command line arguments. sys.argv is a list of the command line arguments, with sys.argv[0] being the script name.

You could accept a command line argument if there is one, otherwise prompt the user for input:

#!/usr/bin/python3
import sys

if len(sys.argv) > 1:
    name = sys.argv[1]
else:
    name = input("Enter name:")

print(name)

You then call the script with a command line argument if needed: ./script.py John.

Answer 3

A simple way is creating a script to input the information:

#!/usr/bin/expect
set cmd [lrange $argv 1 end]
set val [lindex $argv 0]

eval spawn $cmd
expect ":"
send "$val\r";
interact

Save this file somwehere (eg ~/sendInput.sh) and run sudo chmod +x ~/sendInput.sh to make the file executable

now run !/sendInput.sh "Jhon" python script.py This should send the input "Jhon" to the script.py once the character ":" is sent.

(Adpated from https://srvfail.com/how-to-provide-ssh-password-inside-a-script-or-oneliner/)