CODEWITHSUNDEEP
bashfile
Tyler Pierog
Tyler Pierog

Reputation: 537

Storing multiple columns of data from a file in a variable

I'm trying to read from a file the data that it contains and get 2 important pieces of data from the file and use it in a bash script. A string and then a number for example:

Box 12
Toy 85
Dog 13
Bottle 22

I was thinking I could write a while loop to loop through the file and store the data into a variable. However I need two different variables, one for the number and one for the word. How do I get them separated into two variables?

Upvotes: 3

Views: 2579

Answers (3)

Kemin Zhou
Kemin Zhou

Reputation: 6891

Here I provide my own solution which should be discussed. I am not sure this is a good solution or not. Using while read construct has the drawback of starting a new shell and it will not be able to update a variable outside the loop. Here is an example code which you can modify to suite your own need. If you have more column data to use, then slight adjustment is need.

#!/bin/sh

res=$(awk 'BEGIN{OFS=" "}{print $2, $3 }' mytabularfile.tab)

n=0
for x in $res; do 
    row=$(expr $n / 2)
    col=$(expr $n % 2)
    #echo "row: $row column: $col value: $x"
    if [ $col -eq 0 ]; then
        if [ $n -gt 0 ]; then
            echo "row: $row "
            echo col1=$col1 col2=$col2
        fi
        col1=$x
    else
        col2=$x
    fi
    n=$(expr $n + 1)
done
row=$(expr $row + 1)
echo "last row: $row  col1=$col1 col2=$col2"

Upvotes: 0

Charles Duffy
Charles Duffy

Reputation: 295649

To read all the data into a single associative array (in bash 4.0 or newer):

#!/bin/bash
declare -A data=( )
while read -r key value; do
   data[$key]=$value
done <file

With that done, you can retrieve a value by key efficiently:

echo "${data[Box]}"

...or iterate over all keys:

for key in "${!data[@]}"; do
  value=${data[$key]}
  echo "Key $key has value $value"
done

You'll note that read takes multiple names on its argument list. When given more than one argument, it splits fields by IFS, putting columns into their respective variables (with the entire rest of the line going into the last variable named, if more columns exist than variables are named).

Upvotes: 1

Jahid
Jahid

Reputation: 22438

Example code:

#!/bin/bash
declare -a textarr numarr
while read -r text num;do
textarr+=("$text")
numarr+=("$num")
done <file
echo ${textarr[1]} ${numarr[1]} #will print Toy 85

data are stored into two array variables: textarr numarr. You can access each one of them using index ${textarr[$index]} or all of them at once with ${textarr[@]}

Upvotes: 1

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