The string look like
str1= "the value of var1=test, the value of var2=testing, the final value of var3=testing1"
Upto now I split the string by IFS=','
IFS="," read -r -a final <<< "$str1"
Then assigning values to variables
var1="${final[0]#"var1="}"
How to assign the variable values in shortest way using regex?
Expected Output
var1=test
var2=testing
var3=testing1
#!/usr/bin/env bash
str1="the value of var1=test, the value of var2=testing, the final value of var3=testing1"
re='(^|[[:space:]])([[:alpha:]][[:alnum:]]*)=([^, ]+)([, ]|$)(.*)'
remaining=$str1
while [[ $remaining =~ $re ]]; do
varname=${BASH_REMATCH[2]}
value=${BASH_REMATCH[3]}
remaining=${BASH_REMATCH[5]}
printf -v "$varname" %s "$value"
done
# show current values to demonstrate that variables were really assigned
declare -p var1 var2 var3
This works because =~ stores each match group in your regex in a different position in the BASH_REMATCH variable, so we're able to pick out the groups with the names and values and perform an indirect assignment (printf -v varname %s "$value" stores value in varname).
The regex has a fair bit going on, so let's break it down piece-by-piece:
(^|[[:space:]]) ensures that we only match content at the beginning of the string or preceded by a space.([[:alpha:]][[:alnum:]]*)=([^, ]+) matches only assignments where the left-hand side is a valid variable name (a letter, optionally followed by characters that can be either letters or numbers). Because your sample data has commas following values, we know a comma can't be allowed in a value, so we disallow both commas and spaces from being considered part of a value.([, ]|$) allows a variable to terminate either with a comma or space following, or at the end of input.(.*)' matches any remaining content we haven't yet processed, so that content can be run against the regex on the time cycle through the loop.
bash.This is actually one where grep with -E extended regex matching can help, e.g.
grep -E -o 'var[0-9]*[[:blank:]]*=[[:blank:]]*[^,[:blank:]]+' <<< $str
Results in:
var1=test
var2=testing
var3=testing1
The [[:blank:]]* on either side of the '=' just allows for spaces on either side, if present. If there is never a chance of that, you can shorten it to grep -E -o 'var[0-9]*=[^,[:blank:]]+'.
Edit Per-Comment
To store it in var1, simply:
var1=$(grep -E -o 'var[0-9]*[[:blank:]]*=[[:blank:]]*[^,[:blank:]]+' <<< $str)
(or better, store each combination in an array, or create an associative array from the variable names and values themselves) For example, to store all of the var=val combinations in an associative array you could do:
str="the value of var1=test, the value of var2=testing, the final value of var3=testing1"
declare -A array
while read -r line; do
array[${line%=*}]=${line#*=}
done < <(grep -E -o 'var[0-9]*[[:blank:]]*=[[:blank:]]*[^,[:blank:]]+' <<< $str)
for i in ${!array[@]}; do
echo "$i => ${array[$i]}"
done
Example Output
var1 => test
var3 => testing1
var2 => testing
str1=.