how to parse values from text file and assign it for shell script arguments

Question

I have stored some arguments value in sample.txt

1 >> sample.txt
2 >> sample.txt
3 >> sample.txt

I have tried to parse the sample.txt in a shell script file to collect and assign the values to specific variables.

   #!/bin/sh     
   if [ -f sample.txt ]; then

   cat sample.txt | while read Param

   do

   let count++
   if [ "${count}" == 1 ]; then

   Var1=`echo ${Param}`

   elif [ "${count}" == 2 ]; then

   Var2=`echo ${Param}`

   else

   Var3=`echo ${Param}`

   fi

   done

   fi


echo "$Var1"
echo "$Var2"

echo results prints nothing. I would expect 1 and 2 should be printed. Anyone help?

chepner · Accepted Answer · 2015-08-25 15:02:38Z

2

You are running the while loop in a subshell; use input redirection instead of cat:

while read Param; do
  ...
done < sample.txt

(Also, Var1=$Param is much simpler than Var1=$(echo $Param).)

However, there's no point in use a while loop if you know ahead of time how many variables you are setting; just use the right number of read commands directly.

{ read Var1; read Var2; read Var3; } < sample.txt

answered Aug 25, 2015 at 15:02

chepner

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