How to Print a Line Number in Ruby

How to get current file and line number in Ruby?

You'll have to use caller

def mylog(str)
  caller_line = caller.first.split(":")[1]
  puts "#{__FILE__} : #{caller_line} : #{str}"  
end

You'll probably want to know the file from which mylog was called too...

def mylog(str)
  caller_infos = caller.first.split(":")
  puts "#{caller_infos[0]} : #{caller_infos[1]} : #{str}"  
end

Ruby - Read file and print line number

Ruby, like Perl, has the special variable $. which contains the line number of a file.

File.open("file.txt").each do |line|
   puts line, $.
end

Prints:

#Hello
1
#My name is John Smith
2
#How are you?
3

Strip the \n from line if you want the number on the same line:

File.open("file.txt").each do |line|
   puts "#{line.rstrip} #{$.}"
end

#Hello 1
#My name is John Smith 2
#How are you? 3

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As stated in comments, rather than use File.open you can use File.foreach with the benefit of autoclose at the end of the block:

File.foreach('file.txt') do |line|
    puts line, $.
end 
# same output...

How do I print the line number of each line in a string?

Slightly modifying your code, try this:

c1.each_line.with_index do |line, index|
   puts "line: #{index+1}: #{line}"
end

This uses with with_index method in Enumerable.

How do I print the line number of the file I am working with via ARGV?

When Ruby's IO class opens a file, it sets the $. global variable to 0. For each line that is read that variable is incremented. So, to know what line has been read simply use $..

Look in the English module for $. or $INPUT_LINE_NUMBER.

We can also use the lineno method that is part of the IO class. I find that a bit more convoluted because we need an IO stream object to tack that onto, while $. will work always.

I'd write the loop more simply:

File.foreach(ARGV[0]) do |line|

Something to think about is, if you're on a *nix system, you can use the OS's built-in grep or fgrep tool to greatly speed up your processing. The "grep" family of applications are highly optimized for doing what you want, and can find all occurrences, only the first, can use regular expressions or fixed strings, and can easily be called using Ruby's %x or backtick operators.

puts `grep -inm1 abacus /usr/share/dict/words`

Which outputs:

34:abacus

-inm1 means "ignore character-case", "output line numbers", "stop after the first occurrence"

How to Get line number of a word in file using ruby

def get_line_number(file, word)
  count = 0
  file = File.open(file, "r") { |file| file.each_line { |line|
    count += 1
    return count if line =~ /#{word}/
  }}
end

Advantage of reading line by line is when your file is too large, this wont be heavy on your resources.

Return line number with Ruby readline

Maybe something along these lines:

log_snapshot.each_with_index.reverse_each do |line, n|
  case (line)
  when /authorization:/
    puts '%d: %s' % [ n + 1, line ]
  end
end

Where each_with_index is used to generate 0-indexed line numbers. I've switched to a case style so you can have more flexibility in matching different conditions. For example, you can add the /i flag to do a case-insensitive match really easily or add \A at the beginning to anchor it at the beginning of the string.

Another thing to consider using the block method for File.open, like this:

File.open(args[:apache_access_log], "r") do |f|
  f.readlines.each_with_index.reverse_each do |line, n|
    # ...
  end
end

Where that eliminates the need for an explicit close call. The end of the block closes it for you automatically.

Getting current line of code in Ruby

You can use __LINE__ variable. See this https://stackoverflow.com/a/2496240/100466 answer also.

Find line number of key in JSON

Here is the easiest way I found without building your own JSON parser: replace every key entry with unique UUID (alias), then build all combinations of aliases and find that one that returns data from #dig call

keys = path.split('.')
file_content = File.read(file_path).gsub('null', '1111')
aliases = {}

keys.each do |key|
  pattern = "\"#{key}\":"

  file_content.scan(pattern).each do
    alias_key = SecureRandom.uuid
    file_content.sub!(pattern, "\"#{alias_key}\":")

    aliases[key] ||= []
    aliases[key] << alias_key
  end
end

winner = aliases.values.flatten.combination(keys.size).find do |alias_keys|
  # nulls were gsubbed above to make this check work in edge case when path value is null
  JSON.parse(file_content).dig(*alias_keys).present?
end

file_content.split("\n").take_while { |line| line.exclude?(winner.last) }.count + 1

UPD: The snippet above should not work if JSON value by your foo.bar2 keys is false. You should gsub it as well or make this snippet smarter

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