Matching a string with whitespace character in bash-CodePudding

Basically, my goal is to print the rails version as a prompt segment to the terminator(terminal) as we enter a ROR project.

I have figured out a way how to display it as a custom segment in the terminator but I am having difficulty extracting the rails version. And to extract the rails version of a ROR project, there's a file called Gemfile.lock which has a list of ruby gems and the exact rails version it has installed for the app.

This is what a Gemfile.lock looks like:

GEM
  remote: https://rubygems.org/
  specs:
    actioncable (7.0.3.1)
      actionpack (= 7.0.3.1)
      activesupport (= 7.0.3.1)
      nio4r (~> 2.0)
      websocket-driver (>= 0.6.1)
    actionmailbox (7.0.3.1)
      actionpack (= 7.0.3.1)
      activejob (= 7.0.3.1)
      activerecord (= 7.0.3.1)
      activestorage (= 7.0.3.1)
      activesupport (= 7.0.3.1)
      mail (>= 2.7.1)
      net-imap
      net-pop
      ....
      ....
      rails (7.0.3.1)
      actioncable (= 7.0.3.1)
      actionmailbox (= 7.0.3.1)
      actionmailer (= 7.0.3.1)
      actionpack (= 7.0.3.1)
      actiontext (= 7.0.3.1)
      actionview (= 7.0.3.1)
      activejob (= 7.0.3.1)
      activemodel (= 7.0.3.1)
      activerecord (= 7.0.3.1)
      activestorage (= 7.0.3.1)
      activesupport (= 7.0.3.1)
      bundler (>= 1.15.0)
      railties (= 7.0.3.1)
    rails-dom-testing (2.0.3)
      activesupport (>= 4.2.0)
      nokogiri (>= 1.6)
    rails-html-sanitizer (1.4.3)
      loofah (~> 2.3)
    railties (7.0.3.1)
      actionpack (= 7.0.3.1)
      activesupport (= 7.0.3.1)
      method_source
      rake (>= 12.2)
      thor (~> 1.0)
     ....
     ....

The gem I want to extract is rails (7.0.3.1)

I am working on a .zshrc file to extract it and so far I have come up with this solution:

`awk -F' ' '$1~/^rails/{print $0}' Gemfile.lock`

which gives the following output

      rails-dom-testing (~> 2.0)
      rails-html-sanitizer (~> 1.0, >= 1.2.0)
      rails-dom-testing (~> 2.0)
      rails-html-sanitizer (~> 1.1, >= 1.2.0)
    rails (7.0.3.1)
    rails-dom-testing (2.0.3)
    rails-html-sanitizer (1.4.3)
  rails (~> 7.0.3, >= 7.0.3.1)

As you can see there are multiple gems that include the name rails in them. But I only want to extract the version of this gem rails (7.0.3.1) which has a leading 4 space characters in it.

The expected output I am looking for is just the version of the gem like this: 7.0.3.1 without parenthesis and as a string type. This will then be stored in a variable and then I will print it out in the terminal as a custom prompt segment with a custom color like:

local color="%F{#f7507b}"
# ver = ``
echo "%{$color%}$ver"

where ver is the variable that has rails version stored in it.

I have been trying for the past half day but no luck and I have also tried using [[:blank:]] & \s but it doesn't work for this context.

CodePudding user response：

Updated to extract just the version number - 7.0.3.1 - and store in a variable:

$ awk '$1=="rails" {gsub(/[()]/,"",$2); print $2}' Gemfile.lock
7.0.3.1

$ ver=$(awk '$1=="rails" {gsub(/[()]/,"",$2); print $2}' Gemfile.lock)
$ typeset -p ver
declare -- ver="7.0.3.1"

Couple issues with the current code:

-F' ' - not necessary since the default field delimiter is white space, ie, (multiple) spaces and tabs
since the desired line consists of the string rails with white space on each side we can simply use an equality comparison

A few awk ideas:

awk '{ if ($1 == "rails") print $0}' Gemfile.lock
awk '$1 == "rails" { print $0 }' Gemfile.lock
awk '$1 == "rails" { print }' Gemfile.lock
awk '$1=="rails"' Gemfile.lock

All of these generate:

      rails (7.0.3.1)

CodePudding user response：

Using gnu awk you might use for example a pattern with a capture group:

gawk 'match($0, /^[[:space:]]*rails[[:space:]] \(([0-9][0-9.]*)\)/, a) {
  print a[1]
}' Gemfile.lock

Output

7.0.3.1