Ruby: Gsub - multiple string replacements in a single line [in an array]

Question

is there a way to replace multiple strings in a single line of array using gsub.

here is the log file

13:29:00 (alex) OUT: "72500_2010_0F" abcd@S400532  
13:31:12 (alex) IN: "72600_2010_0F" abnc@S403818
13:31:52 (alex) IN: "71200_2010_0F" osa@S400583

I would like to replace the below

(alex) with "" 
OUT:  with OUT
IN: with IN
"72500_2010_0F" with XYZ
"71200_2010_0F" with QWE
"72600_2010_0F" with UIO

The original file (log file) is put into array and I wanted to read each line in the array and perform gsub. Dont want to use Hash as its lil complicated -As being Ruby Beginner...& to Regex...

array1.each do |element|
  i = element.gsub(/?????????/) [ What should go here]
  array2.push(i)
end

I dint want to make changes to original array but push the modified lines into different array i.e array2

What is the best & easy to understand code to do this? - Please help

Why not use file operations to read the file, read every line, replace the content of line with whatever you want and write the new line to a new file ? — Pramod Solanky
– Pramod Solanky, Commented May 8, 2014 at 7:30
How do we do that? - I'm loading file into an array and reading each line array and changing its contents one by one... may be not so good approach yeah? — skumo
– skumo, Commented May 9, 2014 at 0:29

rubish · Accepted Answer · 2014-05-08 08:02:21Z

7

Looking at String#sub it seems there are many ways to do what you want:

One approach can be to use a hash as second parameter

def cleansed_log_line(line)
  replacement_rules = {
    'alex' => '',
    'OUT: ' => 'OUT ',
    'IN: ' => 'IN '
  }
  matcher = /#{replacement_rules.keys.join('|')}/

  line.gsub(matcher, replacement_rules)
end

Another approach can be to to use block form

def cleansed_log_line(line)
  replacement_rules = {
    'alex' => '',
    'OUT: ' => 'OUT ',
    'IN: ' => 'IN '
  }
  matcher = /#{replacement_rules.keys.join('|')}/

  line.gsub(matcher) do |match|
    replacement_rules[match] || match
  end
end

Another not so good implementation

def cleansed_log_line(line)
  replacement_rules = {
    /alex/ => '',
    'OUT: ' => 'OUT ',
    'IN: ' => 'IN '
  }

  replacement_rules.each do |match, replacement|
    line = line.gsub(match, replacement)
  end

  line
end

Hashes and RegEx are nothing to worry about. This function can cleanse any line passed to it and would return a cleansed line.

answered May 8, 2014 at 8:02

rubish

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1 Comment

skumo Over a year ago

hi, like your 1st approach - and is easy to understand. I'm guessing, line.gsub(matcher, replace...) will look into each key in a line and replace this with 'key value' is that right? Thanks for your hlep mate...

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