How to replace text inside another string which matches a regex pattern

Question

${[a-zA-Z0-9._:]*}

I have used the above pattern for grepping words similar to ${SomeText}. How can I replace 'SomeText' with some other string i.e ${SomeText} --> SomeString in my bash script?

Example: file.txt

text text text ${SomeText1} text text ${SomeText2} text text text text text text
text text text text ${SomeText3} text text text text text text ${SomeText4} text
...

my script file:

SomeText1="foo"
SomeText2="bar"
..

I want to replace ${SomeText1} to $SomeText1 which will be replaced by foo. Similarly ${SomeText2} > $SomeText2 > bar

text text text foo text text bar text text text text text text
text text text text baz text text text text text text qux text
...

possible duplicate of [Forcing bash to expand variables in a string loaded from a file](http://stackoverflow.com/questions/10683349/forcing-bash-to-expand-variables-in-a-string-loaded-from-a-file) — Ansgar Wiechers, Jul 27 '13 at 11:36

bartimar · Answer 1 · 2013-07-27T17:14:53.000

You can use sed

echo '${SomeText}, SomeText' | sed "s/\${SomeText}/\${SomeOtherText}/g"

will output

${SomeOtherText}, SomeText

if you need to use variables in sed, do it like this

a="SomeText"
b="SomeOtherText"

echo '${SomeText}, SomeText' | sed "s/\${$a}/\${$b}/g"

The output will be the same as above

EDIT: Better use arrays to store that strings

 SomeText[1]="foo"
 SomeText[2]="bar"

 i=0

 while [[ $i < $MAX_i ]]
 do
   ((i++))
   sed -i "s/\${SomeText[$i]}/${SomeText[$i]}/g"
 done

If you really need your approach, you will need double evaluation

 SomeText[1]="foo"
 SomeText[2]="bar"

 i=0

 while [[ $i < $MAX_i ]]
 do
   ((i++))
   toRepl="SomeText"$i
   scriptToCall=$(eval echo "s/\\\${$toRepl}/$`eval echo ${toRepl}`/g")
   sed -i $scriptToCall file
 done

So you iterate thru all indices (SomeText1, SomeText2, ...), save the current into var toRepl, evaluate the script you want to call, for i=1 it will be scriptToCall="s/\${SomeText[1]}/foo/g" cause you double evaluate toRepl -> ${SomeText1} -> foo and you pass that script to sed :)

Is it clear now?

score 0 · Answer 2 · answered Jul 27 '13 at 12:00

0

You can try this script:

while IFS='=' read k v; do
   v=$(tr -d '"' <<< $v)
   sed -i.bak "s/\${$k}/$v/g" file.txt
done < script

answered Jul 27 '13 at 12:00

anubhava

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How to replace text inside another string which matches a regex pattern

2 Answers2