Vfrdtyky

I'm not used to writing Bash scripts, and Google didn't help in figuring out what is wrong with this script:

#!/bin/bash

while read myline

do

done



echo "Hello"

while read line

do

done



exit 0

The output I get is:

./basic.agi: line 4: syntax error near unexpected token 'done'

./basic.agi: line 4: 'done'

and my bash version is:

GNU bash, version 3.2.25(1)-release (i686-redhat-linux-gnu)

Thank you.

Edit: The script works OK when the while loop isn't empty.

While I'm at it... I expected to exit the loop when the user typed nothing, ie. simply hit the Enter key, but Bash keeps looping. How can I exit the loop?

while read myline

do

        echo ${myline}

done



echo "Hello"

while read line

do

        true

done



exit 0

You can't have an empty loop. If you want a placeholder, just use true.

#!/bin/bash

while read myline

do

    true

done

or, more likely, do something useful with the input:

#!/bin/bash

while read myline

do

    echo "You entered [$line]"

done

As for your second question, on how to exit the loop when the user just presses ENTER with nothing else, you can do something:

#!/bin/bash

read line

while [[ "$line" != "" ]] ; do

    echo "You entered [$line]"

    read line

done

When you are using the read command in a while loop it need input:

echo "Hello" | while read line ; do echo $line ; done

or using several lines:

echo "Hello" | while read line

    do

    echo $line

done

What are you trying to do? From the look of it it seems that you are trying to read into a variable?

This is done by simply stating read the value can then be found inside of $

ex:

read myvar



echo $myvar

As other have stated the trouble with the loop is that it is empty which is not allowed.

This is a way to emulate a do while loop in Bash, It always executes once and does the test at the end.

while

    read -r line

    [[ $line ]]

do

    :

done

When an empty line is entered, the loop exits. The variable will be empty at that point, but you could set another variable to its value to preserve it, if needed.

while

    save=$line

    read -r line

    [[ $line ]]

do

    :

done

If you are looking to create a menu with choices as a infinite loop (with the choice to break out)

PS3='Please enter your choice: '

options=("hello" "date" "quit")

select opt in "${options[@]}"

do

    case $opt in

        "hello") echo "world";;

        "date") echo $(date);;

        "quit")

            break;;

        *) echo "invalid option";;

    esac

done

PS3 is described here

If you type help while in bash you'll get an explanation of the command.