Trying to write a bash script

christianunix · 10-26-2007, 04:32 PM

There is a while loop in the bash script,

and in the while loop the script takes three inputs from the user,

and then when user types letter x then the loop stos.

I have the following so far:

Code:

#!/bin/bash

while echo "first input>"

read firstinput
[ $firstinput != 'x' ]

do 

echo "second input?"

read secondinput

if [ $secondinput = 'x' ]; then

"$firstinput"="x"

fi

echo "third input?"

read thirdinput

if [ $thirdinput = 'x' ]; then

"$thirdinput"="x"

fi

done

but the above isn't working.... I guess I will try the break command

Tischbein · 10-26-2007, 05:00 PM

Try this:

Code:

while true
do
    echo "$PS3"

    stuff

    if [ "$input" = "x" ]
    then
        break
    fi
    # or more compactly:

    [ "$input" = "x" ] && break
done

pixellany · 10-26-2007, 05:08 PM

Quote:

while echo "first input>"
read firstinput
[ $firstinput != 'x' ]
do

The general form of while is:
while <expr>
do
.
.
done

In your case, <expr> is everything in bold, which does not look like it's going to work.

Also, there's nothing to break you out of the loop based on the second and third entries

I would do it like this (pseudo-code---not checked--maybe not even correct BASH...

):

count =1
while [ $count -lt 4 ]
do
echo "enter data: "
if [ $data = "x" ]; then break
else
entry[count] = $data
count += 1
done

The idea is to read into the same variable each time, so you only have one test for "x". When it sees no "x", then it stuffs the data into an array.

Tischbein · 10-26-2007, 05:09 PM

Supplement: man bash tells me that there is also an "until" command, so this would also work and be slightly cleaner:

Code:

NAM=""
until [ "$NAM" = "x" ]
do
    read NAM
    echo "NAM = $NAM"
done

Sometimes it is also a good idea to do the text comparison like this: [ "w$NAM" = "wx" ] because if the variable $NAM is a valid flag for inside a test, e.g. if it's -f, the code might break otherwise. You will have to test to see whether that is a problem for you.

Have fun!

Tischbein · 10-26-2007, 05:22 PM

Nice idea to use arrays! Alas I often am forced against my will to use a shell that doesn't support them. It's called ksh. (deep unhappiness)

If you are going to use a loop then maybe this is an opportunityy for a for ((integer code)) expression. This works and includes pixellany's idea:

Code:

for ((count=1; count <= 3 ; count++ ))
do
    echo "enter data: "
    read data
    [ "$data" = "x" ] && break
    entry[$count]=$data
    echo "Have set array entry $count to ${entry[$count]}"
done

urka58 · 10-26-2007, 05:30 PM

Try this

#!/bin/sh
while [ $1 != x ]; do
# do stuff with $1 ie
echo $1 # or cp $1 /path/to/my/dir or mpg321 $1
shift
done

you just have to pass the script as many parameters as you need adding x for terminating.

usage:

./myscript song_1.mp3 song_2.mp3 song_3.mp3 x

The script will play song_1/2/3 and then stop

This also could be fine
until [-z $1 ]; do
echo $1 # same as before
shift
done

This don't even need a terminating parameter

Ciao