Print values in Array Bash Script [duplicate]

Question

My file Threadout.txt contains like Thread 1/1/25/100

val1=$(grep 'Thread' Threadout.txt | awk -F"/" '{print $1}')  
val2=$(grep 'Thread' Threadout.txt | awk -F"/" '{print $2}')    
val3=$(grep 'Thread' Threadout.txt | awk -F"/" '{print $3}')  
val4=$(grep 'Thread' Threadout.txt | awk -F"/" '{print $4}')

for((i=1;i<5;i++))  
do  
  val[i]=$(grep 'Thread' Threadout.txt | awk -F"/" '{print $[i]}')  
  echo $val[i] 
done

I have tried this array but not giving the correct result like 1 1 25 100 values. Any error?

Answer 1

There are several issues with your code.

• The first important thing to remember is that since your awk program is enclosed in single quotes (which is recommended), no shell parameter expansions take place, and your statement print $[i] will not work. See this exhaustive Q&A on StackOverflow on how to use shell parameter in awk programs.
• Even so, an awk field whose number is stored in a (awk) variable n would be addressed via $n, not $[n].
• You assign the variables val1 to val4 but never actually use them, so the first part of your script example doesn't do anything.
• Finally, to dereference an array variable, you have to state ${val[i]}, not $val[i] (which would print the content of the variable $val- the empty string - followed by the fixed string [i]).

There are also several inefficiencies such as the repeated call to awk and (as far as I can tell) a failure to address the issue of the leading Thread in your example input when using just / as field separator.

To address these issues, and since the relevant values do not contain whitespace in your example, try the following:

#!/bin/bash

val=( $(awk '/^Thread/{n=split($2,a,/\//); for (i=1;i<=n;i++) printf("%s%s",a[i],OFS)}' Threadout.txt) )

for i in ${!val[@]}
do
    echo "${val[i]}"
done

• The awk call will split the second "field" of the line Thread 1/1/25/100, namely the 1/1/25/100 part at the / into the array a and print all entries of the array, separated by OFS (which defaults to space).
• The shell script will take the output of that awk program and - since it is a space-separated list of tokens - assign the individual tokens to an array variable val via the val=( ... ) statement.
• It will then iterate over the array indices and print the array values.

You may want to read into bash arrays a little further in the GNU Bash Reference Manual, or GreyCat&Lhunath's Bash Guide. I would also recommend you to take a look at shellcheck to debug your shell scripts.