How to format cat command as a table in bash-CodePudding

I have the following code that parses XML to display the node value of each element in a file.

#Abbreviation - symbol
cat elements/*.xml |  egrep "<symbol>.*</symbol>" |sed -e "s/<symbol>\(.*\)<\/symbol>/\1/"|tr "|" " "

#Weight - atomic-weight
cat elements/*.xml |  egrep "<atomic-weight>.*</atomic-weight>" |sed -e "s/<atomic-weight>\(.*\)<\/atomic-weight>/\1/"|tr "|" " "

#Number atomic-number
cat elements/*.xml |  egrep "<atomic-number>.*</atomic-number>" |sed -e "s/<atomic-number>\(.*\)<\/atomic-number>/\1/"|tr "|" " " > number

How can I format the three of these outputs as a table instead of one huge sequential list?

Sample Data -

File1 -

  <symbol>Ag</symbol>
  <atomic-number>47</atomic-number>
  <atomic-weight>107.8682</atomic-weight>

File2 -

  <symbol>Ba</symbol>
  <atomic-number>56</atomic-number>
  <atomic-weight>137.327</atomic-weight>

Desired Output -

Symbol   Number   Weight
Ag       47       107.8682
Ba       56       137.327

CodePudding user response：

Try this:

#!/bin/bash

printf '%-9s %-9s %-9s\n' "Symbol" "Number" "Weight"

for F in *.xml
do
    symbol=$(grep -E "<symbol>.*</symbol>" "$F"               | sed -e "s/.*<symbol>\(.*\)<\/symbol>.*/\1/")
    number=$(grep -E "<atomic-number>.*</atomic-number>" "$F" | sed -e "s/.*<atomic-number>\(.*\)<\/atomic-number>.*/\1/")
    weight=$(grep -E "<atomic-weight>.*</atomic-weight>" "$F" | sed -e "s/.*<atomic-weight>\(.*\)<\/atomic-weight>.*/\1/")

    printf '%-9s %-9s %-9s\n' "$symbol" "$number" "$weight"
done

printf allows you to format the width and alignment in that width of printed text (or number, or floats, ...).
to avoid any interpretation of weight values (i.e. number of decimals for example), all values are printed as strings.
for printf, '%-9s' means it will print the value using 9 chars wide, left aligned. Without the -, it will align right.
printf does not output a carriage return unless you tell it to, which explains the \n.
I reused your grep ... | sed ... commands, but for 2 details. 1 Used grep -E instead of egrep. 2 Added .* at the beginning and end of your sed to eliminate prefixes or suffixes to the <SOMETHING> tags.

The output I get is:

$ ./so.bash 
Symbol    Number    Weight   
Ag        47        107.8682 
Ba        56        137.327