How to grep for a pattern in a file and store the content following it?

Question

My file content is

blablabla    
Name  : 'XYZ'  
Age   : '30'  
Place : 'ABCD'    
blablabla

How can I grep for "Name", "Age", "Place" and store name "XYZ", age "30" and place "ABCD" in a hash?

What should be the '?' in this code to get those?

data = {}
name = /Name/
age = /Age/
place = /Place/
read_lines(file) { |l|
  case l
    when name
      data[:name] = ?
    when age
      data[:age] = ?
    when place
      data[:place]= ?
  end
}

How many groups of these lines are there in the file? Just one, or will there be many? How big are the files? — the Tin Man, Jun 09 '16 at 22:43

Lukas Baliak · Accepted Answer · 2016-06-09T14:52:49.463

0

You can use something like this.

data = {}
keys = {:name => "Name", :age => "Age", :place => "Place"}

File.open("test.txt", "r") do |f|
  f.each_line do |line|
    line.chomp!
    keys.each do |hash_key, string|
      if line[/#{string}/]
        data[hash_key] = line.strip.split(" : ")[-1].gsub("'", "")
        break
      end
    end
  end
end

output

p data
# => {:name=>"XYZ", :age=>"30", :place=>"ABCD"}

edited Jun 09 '16 at 14:52

answered Jun 09 '16 at 12:17

Lukas Baliak

2,849
2
23
26

Ruby has a method specifically for removing line endings: `String#chomp`. `line.gsub!("\n", "")` is overkill here. – Jordan Running Jun 09 '16 at 14:35
It's `chomp!`, not `chop!`. – Jordan Running Jun 09 '16 at 14:48

Mike S · Answer 2 · 2016-06-09T12:51:15.550

0

Strange code, but in this case:

  data[:name] = l.split(':')[1] if l.match(name)
when age
  data[:age] = l.split(':')[1] if l.match(age)
when place
  data[:place]= l.split(':')[1] if l.match(place)

Are you interested in refactoring?

One option is to:

mapping =
    [
        { name: :name, pattern: /Name/ },
        { name: :age, pattern: /Age/ },
        { name: :place, pattern: /Place/ }
    ]
data = str.split(/\r?\n|\r/).map do |line|
  mapping.map{|pair|
    { pair[:name] => line.split(' : ')[1].gsub("'", "") } if line.match(pair[:pattern])
  }.compact.reduce({}, :merge)
end.reduce({}, :merge)

edited Jun 09 '16 at 12:51

answered Jun 09 '16 at 12:17

Mike S

324
1
10

why you use `case` and after if `if l.match` ? – Lukas Baliak Jun 09 '16 at 12:26
The question was to fill question marks. I bet that code needs to be rewritten in general. – Mike S Jun 09 '16 at 12:29
I agree, but i just ask why to use `case` with rgx and after that use `if l.match` ;) – Lukas Baliak Jun 09 '16 at 12:34

score 0 · Answer 3 · answered Jun 09 '16 at 15:44

Suppose we first read the file into a string:

str = File.read('fname')

which is:

str =<<_
blablabla
Name : 'XYZ'
Age : '30'
Place : 'ABCD'
blablabla
_
  #=> "blablabla\nName : 'XYZ'\nAge : '30'\nPlace : 'ABCD'\nblablabla\n"

Then use the regex

r = /
    ^                    # match beginning of line 
    Name\s*:\s*'(.*)'\n  # match 'Name`, ':' possibly surrounded by spaces, any number
                         # of any character in capture group 1, end of line
    Age\s*:\s*'(.*)'\n   # match 'Age`, ':' possibly surrounded by spaces, any number
                         # of any character in capture group 2, end of line
    Place\s*:\s*'(.*)'\n # match 'Place`, ':' possibly surrounded by spaces, any number
                         # of any character in capture group 3, end of line
    /x                   # free-spacing regex definition mode

with String#scan to form the hash:

[:name, :age, :place].zip(str.scan(r).first).to_h
  #=> {:name=>"XYZ", :age=>"30", :place=>"ABCD"}

the Tin Man · Answer 4 · 2016-06-09T22:57:43.843

I'd do something like this:

str = <<EOT
blablabla    
Name  : 'XYZ'  
Age   : '30'  
Place : 'ABCD'    
blablabla  
EOT

str.scan(/(Name|Age|Place)\s+:\s'([^']+)/).to_h  # => {"Name"=>"XYZ", "Age"=>"30", "Place"=>"ABCD"}

scan will create sub-arrays if it sees pattern groups in the regular expression. Those make it easy to turn the returned array of arrays into a hash.

If you need to fold the keys to lower-case, or convert them to symbols:

str.scan(/(Name|Age|Place)\s+:\s'([^']+)/)
  .map{ |k, v| [k.downcase, v] } # => [["name", "XYZ"], ["age", "30"], ["place", "ABCD"]]
  .to_h  # => {"name"=>"XYZ", "age"=>"30", "place"=>"ABCD"}

Or:

str.scan(/(Name|Age|Place)\s+:\s'([^']+)/)
  .map{ |k, v| [k.downcase.to_sym, v] } # => [[:name, "XYZ"], [:age, "30"], [:place, "ABCD"]]
  .to_h  # => {:name=>"XYZ", :age=>"30", :place=>"ABCD"}

Or some variation on:

str.scan(/(Name|Age|Place)\s+:\s'([^']+)/)
   .each_with_object({}){ |(k,v), h| h[k.downcase.to_sym] = v}
# => {:name=>"XYZ", :age=>"30", :place=>"ABCD"}

If the example string truly is the complete file, and there won't be any other reoccurrence of the key/value pairs, then this will work. If there could be more than one then the resulting hash will not be correct because the subsequent pairs will stomp on the first one. If the file is as you said, then it'll work fine.

How to grep for a pattern in a file and store the content following it?

4 Answers4