CODEWITHSUNDEEP
linuxstringbashawk
rlvamsi
rlvamsi

Reputation: 179

Extract number from String in bash

I want to extract a number from a string and use that number for future calculations

while IFS= read line ; do  

  if [[ "$line" == Content-Length* ]]
  then
  size=$(echo "$line" | awk '{print $2}')   
  echo "$size"
  let size=$size+1  
  echo "$size"
  break
  fi    
done <files

files has the line 

Content-Length: 4806

but output looks like this 

4806
+1")syntax error: invalid arithmetic operator (error token is "
4806

i tried this for more than 5 hrs but could find why is this happening .can some one tell me why

Upvotes: 0

Views: 658

Answers (2)

Sidorov Andrew
Sidorov Andrew

Reputation: 11

you can replace: 

let size=$size+1

to

let size=$[$size+1]

or

let size=$[size+1]

or

let size++

or 

let size=`expr $size + 1`

All example run fine on ubuntu 13.04 and you example too.

Upvotes: 0

chepner
chepner

Reputation: 531075

You can take advantage of the fact that Content-Length: 4806 is actually a space-delimited pair of strings.

while read -r field value; do
    if [ "$field" = "Content-Length" ]; then
        echo "$size"
        echo "$((size+1))"
    fi
done < files

To solve the problem of DOS line endings, either run the file through dos2unix or some other tool to fix the line endings, or trim the carriage return using

size=${size%.}

which will remove the final character of size from its value. Fixing the file, rather than coding around it, is recommended.

Upvotes: 2

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