How can I parse a string using bash to get a number

Question

I have the following string:

PR-1769|7bb12d4152a497cef491e0a1088b3984ad92972f|jaga|

How can I parse the string above using bash so that I get t

Answer 1

There's no need for grep here: bash has built-in regex support, which is vastly more efficient to use than starting up an external utility just to process a single line:

re='^PR-([0-9]+)'
s='PR-1769|7bb12d4152a497cef491e0a1088b3984ad92972f|marvel|'

if [[ $s =~ $re ]]; then
  echo "Matched: ${BASH_REMATCH[1]}"
fi

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You can also use parameter expansions:

s='PR-1769|7bb12d4152a497cef491e0a1088b3984ad92972f|marvel|'
s="${s%%'|'*}" # trim off everything after the first |
s="${s#PR-}"   # trim off the leading PR
echo "$s"

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If you needed to extract the individual fields, by the way, read might be the correct tool for the job:

s='PR-1769|7bb12d4152a497cef491e0a1088b3984ad92972f|marvel|'
IFS='|' read -r pr hash username <<<"$s"

...the above will put PR-1769 into the variable pr, 7bb12d4152a497cef491e0a1088b3984ad92972f into the variable hash, and marvel into the variable username. To strip off the PR-, then, might simply look like:

echo "${pr#PR-}"

...or, to print the extracted username:

echo "$username"

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See:

• BashFAQ #100 ("How do I do string manipulations in bash?")
• bash-hackers.org parameter expansion reference