BashScripting: Reading out a specific variable

Question

my question is actually rather easy, but I suck at bash scripting and google was no help either. So here is the problem: I have an executable that writes me a few variables to stdout. Something like that:

MrFoo:~$ ./someExec 
Variable1=5
Another_Weird_Variable=12
VARIABLENAME=42

What I want to do now is to read in a specific one of these variables (I already know its name), store the value and use it to give it as an argument to another executable.

So, a simple call like

./function2 5  // which comes from ./function2 Variable1 from above

I hope you understand the problem and can help me with it

jaypal singh · Accepted Answer · 2012-01-09 20:12:28Z

2

With awk you can do something like this (this is for passing value of 1st variable)

./someExec | awk -F= 'NR==1{system("./function2 " $2)}'

or

awk -F= 'NR==1{system("./function2 " $2)}' <(./someExec)

edited Jan 9, 2012 at 20:12

answered Jan 9, 2012 at 19:56

jaypal singh

77.6k24 gold badges108 silver badges147 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Palpatim · Accepted Answer · 2012-01-09 19:57:46Z

Easiest way to go is probably to use a combination of shell and perl or ruby. I'll go with perl since it's what I cut my teeth on. :)

someExec.sh

#!/bin/bash
echo Variable1=5
echo Another_Weird_Variable=12
echo VARIABLENAME=42

my_shell_script.sh

#!/bin/bash
myVariable=`./someExec | perl -wlne 'print $1 if /Variable1=(.*)/'`
echo "Now call ./function2 $myVariable"

[EDIT] Or awk, as Jaypal pointed out 58 seconds before I posted my answer. :) Basically, there are a lot of good solutions. Most importantly, though, make sure you handle both security and error cases properly. In both of the solutions so far, we're assuming that someExec will provide guaranteed well-formed and innocuous output. But, consider if someExec were compromised and instead provided output like:

./someExec
5 ; rm -rf / # Uh oh...

anubhava · Accepted Answer · 2012-01-09 20:05:18Z

1

You can use awk like this:

./function2 $(./someExec | awk -F "=" '/Variable1/{print $2}')

which is equivalent to:

./function2 5

answered Jan 9, 2012 at 20:05

anubhava

790k67 gold badges603 silver badges671 bronze badges

Comments

Kambus · Accepted Answer · 2012-01-10 09:51:06Z

1

If you can make sure someExec's output is safe you can use eval.

eval $(./someExec)
./function2 $Variable1

answered Jan 10, 2012 at 9:51

Kambus

3,6921 gold badge19 silver badges10 bronze badges

Comments

Marek Grzenkowicz · Accepted Answer · 2012-01-10 09:37:58Z

0

You can use this very simple and straight forward way:

./exp1.sh | grep "Variable1" | awk -F "=" '{print $2}'

edited Jan 10, 2012 at 9:37

Marek Grzenkowicz

17.4k11 gold badges88 silver badges118 bronze badges

answered Jan 10, 2012 at 9:31

Enigma

711 gold badge2 silver badges4 bronze badges

Comments

k_vishwanath · Accepted Answer · 2018-12-24 16:36:55Z

0

If you want to use only one variable from the file use the below

eval $(grep 'Variable1' ./someExec )
./function2 $Variable1

And, if you want to use all the variables of a file, use

eval $(./someExec)
./function2 $<FILE_VARIBALE_NAME>

answered Dec 24, 2018 at 16:36

k_vishwanath

1,6253 gold badges22 silver badges32 bronze badges

Collectives™ on Stack Overflow

BashScripting: Reading out a specific variable

6 Answers 6

Comments

someExec.sh

my_shell_script.sh

Comments

Comments

Comments

Comments

Comments

Hot Network Questions

Collectives™ on Stack Overflow

6 Answers 6

Comments

someExec.sh

my_shell_script.sh

Comments

Comments

Comments

Comments

Comments

Related