Bash assigning array in loop

mp85 · 12-09-2014, 12:58 PM

input.txt

Code:

x1=1658
x12=1658
x21=9795
x5=18322
x77=3265
x68=6001
x30=123
x3=8091
x4=636739

Code:

for (( i = 1; i <= $n; i++ ))
	do
	echo 'Pick from above list'
	read value
	arr_val=($(sed 's/=/ /g' input.txt | grep -w "$value" | awk '{print $2}'))
       done

echo ${arr_val[@]}

So the user would input the number of values they want as $n then which values they want x21 and x38 for example.
Using Bash all I want to to do is create an array from the output above but when i use echo to check, it only seems to be outputting the last value

Ive tried setting arr_val[$i]=($(sed........)
But that is giving me an error

Does anyone have any advice?

Thanks

pan64 · 12-10-2014, 02:50 AM

sorry, I do not really understand what do you need.

jags1984 · 12-10-2014, 05:37 AM

Your program looks complicated... try this.

#!/bin/bash

i=0
while read LINE
do
arr1[$i]=`echo $LINE | cut -d"=" -f2`
i=`expr $i + 1`
done < input.txt

grail · 12-10-2014, 06:04 AM

I am with pan64 in that from your explanation and your example code it is difficult to follow what you are trying to do?

As far as your array goes, every time your loop hits arr_val=() it is resetting the values in the array to the latest read, hence
after you finish the loop you will only have then values from the last read

mp85 · 12-10-2014, 10:07 AM

Quote:

Originally Posted by grail

I am with pan64 in that from your explanation and your example code it is difficult to follow what you are trying to do?

As far as your array goes, every time your loop hits arr_val=() it is resetting the values in the array to the latest read, hence
after you finish the loop you will only have then values from the last read

Sorry, Ill try to explain it better but essentially i just dont want it to be resetting the values. I want that each time it goes through the loop it is outputting to a different row of the array. So I guess more like how I have it below for assigning the array (though this gives me an error).

Code:

read n

for (( i = 1; i <= $n; i++ ))
	do
	echo 'Pick from above list'
	read value
	arr_val[$i]=($(sed 's/=/ /g' input.txt | grep -w "$value" | awk '{print $2}'))
       done

echo ${arr_val[@]}

So say the user says n=4.
Then they would input there 4 choices. For example:
x12
x5
x68
x30

The desired array output would be:
1658
18322
6001
123

Maybe Im going about it all wrong, but I hope that clears up what I am trying to get at

Thanks

pan64 · 12-10-2014, 10:36 AM

so you want to get a number <n>, and read <n> lines from that input file. All the <n> inputs will be asked, as column 1 and column 2 will be put into your array.

Code:

for (( i = 1; i <= $n; i++ ))
do
	echo 'Pick from above list'
	read value
        arr_val[$i]=$(awk -F= -v var="$value" '$1==var{print $2}' input.txt)
done

probably works, but still not really sure. Also there is no error handling here, what will happen if user entered an illegal value?

mp85 · 12-10-2014, 11:11 AM

Quote:

Originally Posted by pan64

so you want to get a number <n>, and read <n> lines from that input file. All the <n> inputs will be asked, as column 1 and column 2 will be put into your array.

Code:

for (( i = 1; i <= $n; i++ ))
do
	echo 'Pick from above list'
	read value
        arr_val[$i]=$(awk -F= -v var="$value" '$1==var{print $2}' input.txt)
done

probably works, but still not really sure. Also there is no error handling here, what will happen if user entered an illegal value?

Awesome! That worked, though I have no idea why it did versus what I had. I was under the impression my job was not working because it didnt like the

Code:

arr_val[$i]=

As for errors, seems that if they put in something that doesn't exist for value it just write out $value instead which seems ok as it would pretty noticeable

Thanks Again!

pan64 · 12-10-2014, 11:17 AM

you made an extra ( ) around that expression.

Code:

v=$(awk -F= -v var="$value" '$1==var{print $2}' input.txt)
if [ -z "$v" ] # here comes your error handling
else
arr_val[$i]="$v"

grail · 12-10-2014, 07:27 PM

Assuming using bash v4+, you could use associative arrays and keep it all in bash:

Code:

declare -A input_array

while IFS== read -r index value
do
  input_array[$index]="$value"
done<input.txt

for (( i = 0; i < n; i++ ))
do
  echo 'Pick from above list'
  read value
  
  arr_val+=( ${input_array[$value]:-$value does not exist} )
done

I leave you to set 'n' and I assume at some point you do actually display the 'above list' (tip: you could use the while loop above to display it)