CODEWITHSUNDEEP
linuxbash
Remco
Remco

Reputation: 203

How to assign the result of echo to a variable in bash script

I'm a Linux newbie and have copied a bash script that extracts values from a XML. I can echo the result of a calculation perfectly, but assigning this to a variable doesn't seem to work.

#!/bin/bash
IFS=$'\r\n' result=(`curl -s "http://xxx.xxx.xxx.xxx/smartmeter/modules" | \
xmlstarlet sel -I -t -m "/modules/module" \
    -v "cumulative_logs/cumulative_log/period/measurement" -n \
    -v "point_logs/point_log/period/measurement" -n | \
sed '/^$/d' `)

# uncomment for debug
echo "${result[0]}"*1000 |bc 
gas=$(echo"${result[0]}"*1000 |bc)

echo "${result[0]}"*1000 |bc

Gives me the result I need, but I do not know how to assign it to a variable.

I tried with tick marks:

gas=\`echo"${result[0]}"*1000 |bc\`

And with $(

Can somebody point me in the right direction?

Upvotes: 20

Views: 41777

Answers (2)

fedorqui
fedorqui

Reputation: 290525

There is no need to use bc nor echo. Simply use the arithmetic expansion $(( expression )) for such operations:

gas=$(( ${result[0]} * 1000))

This allows the evaluation of an arithmetic expression and the substitution of the result.

Upvotes: 9

Ijaz Ahmad
Ijaz Ahmad

Reputation: 12130

If you want to use bc anyway then you can just use back ticks , why you are using the backslashes? this code works , I just tested. 

  gas=`echo ${result[0]}*1000 | bc`

Use one space after echo and no space around * operator

Upvotes: 24

Related Questions