Sammy no longer has the balloon it flew away. The sub method replaces part of a string with another. You can do that in Ruby with the sub and gsub methods. The find and replace feature in word processors lets you search for a string and replace it with another string. Sometimes it's useful to work with the individual characters of a string. String = '' string 'hello' string ' ' string 'there' # 'hello there' Don't use += for string concatenation because that will create a new string every time, which is not good for performance! Iterate Over Characters Of a String in Ruby. These methods take two arguments, the search string and the replacement string. The gsub and gsub! methods provide another quick and easy way of replacing a substring with another string. That means loading one line at a time, instead of the whole file.įind.find takes a string containing a path, and will pass the parent path along with the path of each file and sub-directory to an accompanying block. You should avoid file slurping when dealing with large files.

Ruby search file for stringįile.open(filename).grep(/string/) This loads the whole file into memory (slurps the file). Read the file, the whole file, line by line, or a specific amount of bytes. By default, grep displays the matching lines, and it may be used to search for lines of text matching one/many regular expressions in a fuss-free, and it outputs only the matching lines. The grep command is primarily used to search text or search any given file for lines containing a match to the supplied words/strings. Now let's try to read this file − #!/usr/bin/ruby aFile = File.new('input.txt', 'r') if aFile content = aFile.sysread(20) puts content else puts 'Unable to open file!' end This statement will output the first 20 characters of the file. Find.find takes a string containing a path, and will pass the parent path along with the path of each file and sub-directory to an accompanying block.įollowing is the input text file − This is a simple text file for testing purpose. RubyMine places the highlighted string into the search field. Alternatively, in the editor, highlight the string you want to find and press Ctrl+F.

RubyMine highlights the results of your search in the file. In the search field that opens, enter your search string. It's prone to various failure scenarios, such as data loss in case of a crash, interrupt, or disk being full. Disclaimer: This approach is a naive illustration of Ruby's capabilities, and not a production-grade solution for replacing strings in files.

Ruby find word in file