shell脚本：检查变量，然后执行交互模式

Question

I am writing a utility that can run in command line or interactive mode. In the code, I'd like to check if interactive flag is set and then echo the questions to the User for reading the input. However, for ever question , i dont want to check interactive flag with if condition. In bash script, is there a more efficient way to achieve this ?

Any pointers are greatly appreciated!

Thank you

Answer 1

Something like this maybe?

#! /bin/bash

function interactive {
    shift
    while read line; do
        something with $line
    done
}

getopts 'i' option
[[ $option = 'i' ]] && interactive "$@"

Note that this isn't the best style if you have multiple options. In that case use while getopts and shift using argument index.

Answer 2

If you want to tell if the shell is in "interactive mode", as defined by the shell, then you can use something like:

case $- in
        *i*) # Interactive
             ;;
        *)   # Non-interactive
             ;;
esac

This, however, is probably not what you want. Shell scripts, for example, are, by default, "non-interactive".

If you want to know if you can ask the user a question, then you are more interested in finding out if stdin is connected to a terminal. In that case, you can use the -t test on file descriptor zero (which is standard input):

if [ -t 0 ]
then
        # Interactive: ask user
        read -p "Enter a color: " color
        read -p "Enter a number: " number
else
        # Non-interactive: assign defaults
        color="Red"
        number=3
fi

echo "color=$color and number=$number"

If there is the possibility that your script might be run remotely over, say, ssh , then a slightly more complicated test is needed:

if [ -t "$fd" ] || [ -p /dev/stdin ]
then
    echo interactive
else
    echo non-interactive
fi