Use GNU grep to count the length of substring between two words

Note: the command below requires GNU grep, it is available on Linux by default. On Mac OS, you need to install it manually using

brew install grep

and command is called ggrep instead of grep.

Get the substring between two words

echo "<person><name>abc</name></person>" | grep -o -P '(?<=<name>).*(?=</name>)'

Output should be:

abc

Count the length of substring

echo "<person><name>abc</name></person>" | grep -o -P '(?<=<name>).*(?=</name>)' | wc -c

Output should be:

3

Count substring lengths for each line

cat multi-lines.txt | while read line; do echo $line | grep -o -P '(?<=<name>).*(?=</name>)' | wc -c; done

see also

• How to use sed/grep to extract text between two words?
• How to install and use GNU Grep in macOS