Home / ubuntu / Questions / 60729
In Process
mpen
Asked: 2011-09-10 09:35:43 +0800 CST

How to pass answers to CLI script via arguments?

  • 772

I'm writing a CLI script that asks a series of questions before doing a few things. How can I pass them as arguments so that I don't have to keep entering them every time I want to test my script?

Basically, it should pass 4 items to STDIN, like "text1[ENTER]text2[ENTER]text3[ENTER]text4[ENTER]" automatically.

Yes, I could modify my script to actually read the shell arguments, but I don't want to do it that way, since it's supposed to run more like a wizard.

Looking for something like

SOMEPROGRAM myscript arg1 arg2 arg3 arg4

or

SOMEPROGRAM arg1 arg2 arg3 arg4 | myscript

Or something like that. Is there such a program?

command-line

7 Answers

  1. I understand you do not want to modify myscript.

    Regarding the second solution you ask for, you can use printf:

    printf '%s\n' text1 text2 text3 text4 | myscript

    so that, defining an alias for SOMEPROGRAM as:

    alias SOMEPROGRAM="printf '%s\n'"

    you could effectively call

    SOMEPROGRAM text1 text2 text3 text4 | myscript

    The first form is ambiguous (from the point of view of SOMEPROGRAM), because it don't know where myscript options end and text parameters start, unless myscript is effectively invoked without any options. In this case you could use a function:

    SOMEPROGRAM() {
  myscript="$1"
  shift
  printf '%s\n' "$@" | "$myscript"
}

    so that you could effectively call

    SOMEPROGRAM myscript text1 text2 text3 text4
    • 6

  2. So basically, you want to pass each argument as a line to a child program. Below is a script that loops through all arguments passed ti SOMEPROGRAM and prints them as a line. You can pass an empty line ("enter without entering something before") by passing an empty argument as in SOMEPROGRAM yes '' | myscript.

    #!/bin/bash
# This is "SOMEPROGRAM", it prints each argument as "answer" to  a program that
# must be piped. Usage: SOMEPROGRAM yes 1 no 2 | myscript
for arg; do
    echo "$arg"
done

    If you always need to answer "yes" to your script, use the coreutil yes:

    yes | myscript

    If you need to pass some other value, say "no":

    yes 'no' | myscript
    • 2

  3. You can pass the parameters, but it won't work, you'll also have to modify the bash script to accept the params from the command-line as well.

    • 1

  4. If you are writing a script then just use getopts so the arguments are passed to the scripts and then you can use those args as you want? Is this something you are looking for?

    http://wiki.bash-hackers.org/howto/getopts_tutorial

    • 1

  5. For simple cases, the way enzotib describes it with piping stdin from a file seems reasonable. Consider this script:

    #!/bin/bash
read -p "What's your name?" name 
echo $name 
read -p "Age?" age 
echo $age
echo "Your name is " $name " and your age is "$age

    invoke it with:

    echo -e "Foobar\n14\n" | ./namenage.sh

    The -e is to enable escape sequences like \newline. 

    Foobar
14
Your name is  Foobar  and your age is 14

    Note how magically, bash doesn't print the prompt for reading.

    However, for more complicated cases, there is a program, called expect to handle interactive CLI programs, where you have to wait for the next prompt, before entering the second value, and I guess you can even branch under conditions.

    • 1

  6. With bash, you can do this:

    myscript << END
arg1 
arg2
arg3
arg4
END

    or

    myscript <<< $'arg1\narg2\narg3\narg4\
    • 1

  7. I'm pretty sure you're looking for expect.

    edit: example added

      
#!/bin/bash  
USER="root"  
HOST="192.168.1.111"  
PASS="secret"  
expect -c "  
spawn ssh $USER@$HOST  
expect \"password:\"  
send \"$PASS\r\"  
interact  
"

    --from this blog

    • 1