Append File

Opening a file in append mode adds text after the existing content.
append mode Append mode keeps existing file content and writes new content at the end.
                            extra_line
                            extra_line = "third" (default)extra_line = "bonus"extra_line = "done"
                        

                            append_file.rb
                        
Replay: real traced execution (multi-file project)

                            require "tmpdir"

extra_line = "third"

Dir.mktmpdir do |dir|
  path = File.join(dir, "log.txt")
  File.write(path, "first\nsecond\n")

  file = File.open(path, "a")
  file.puts extra_line
  file.close

  lines = File.read(path).split("\n")

  puts "file=#{File.basename(path)}"
  puts "lines=#{lines.join(",")}"
  puts "last=#{lines.last}"
end
require "tmpdir"

extra_line = "bonus"

Dir.mktmpdir do |dir|
  path = File.join(dir, "log.txt")
  File.write(path, "first\nsecond\n")

  file = File.open(path, "a")
  file.puts extra_line
  file.close

  lines = File.read(path).split("\n")

  puts "file=#{File.basename(path)}"
  puts "lines=#{lines.join(",")}"
  puts "last=#{lines.last}"
end
require "tmpdir"

extra_line = "done"

Dir.mktmpdir do |dir|
  path = File.join(dir, "log.txt")
  File.write(path, "first\nsecond\n")

  file = File.open(path, "a")
  file.puts extra_line
  file.close

  lines = File.read(path).split("\n")

  puts "file=#{File.basename(path)}"
  puts "lines=#{lines.join(",")}"
  puts "last=#{lines.last}"
end

                        
1extra_line ← third1require "tmpdir"23extra_line→ third = "third"  #@extra_line="bonus", "done"45Dir.mktmpdir do |dir|6  path = File.join(dir, "log.txt")7  File.write(path, "first\nsecond\n")89  file = File.open(path, "a")10  file.puts extra_line11  file.close1213  lines = File.read(path).split("\n")1415  puts "file=#{File.basename(path)}"16  puts "lines=#{lines.join(",")}"17  puts "last=#{lines.last}"18end⋯
2path ← /tmp/⟨tmp A⟩/log.txt, file ← #<File:/tmp/⟨tmp A⟩/log.txt>⋯5Dir.mktmpdir do |dir/tmp/⟨tmp A⟩|6  path→ /tmp/⟨tmp A⟩/log.txt = File.join(dir, "log.txt")/tmp/⟨tmp A⟩/log.txt7  File.write(path/tmp/⟨tmp A⟩/log.txt, "first\nsecond\n")89  file→ #<File:/tmp/⟨tmp A⟩/log.txt> = File.open(path/tmp/⟨tmp A⟩/log.txt, "a")10  file.puts extra_line(empty)11  file.close1213  lines→ ["first", "second", "third", "third", "third"] = File.read(path).split("\n")["first", "second", "third", "third", "third"]1415  puts "file=#{File.basename(path)log.txt}"16  puts "lines=#{lines.join(",")first,second,third,third,third}"17  puts "last=#{lines.lastthird}"18end⋯outputfile=log.txt
lines=first,second,third,third,third
last=third
1extra_line ← bonus1require "tmpdir"23extra_line→ bonus = "bonus"45Dir.mktmpdir do |dir|6  path = File.join(dir, "log.txt")7  File.write(path, "first\nsecond\n")89  file = File.open(path, "a")10  file.puts extra_line11  file.close1213  lines = File.read(path).split("\n")1415  puts "file=#{File.basename(path)}"16  puts "lines=#{lines.join(",")}"17  puts "last=#{lines.last}"18end⋯
2path ← /tmp/⟨tmp A⟩/log.txt, file ← #<File:/tmp/⟨tmp A⟩/log.txt>⋯5Dir.mktmpdir do |dir/tmp/⟨tmp A⟩|6  path→ /tmp/⟨tmp A⟩/log.txt = File.join(dir, "log.txt")/tmp/⟨tmp A⟩/log.txt7  File.write(path/tmp/⟨tmp A⟩/log.txt, "first\nsecond\n")89  file→ #<File:/tmp/⟨tmp A⟩/log.txt> = File.open(path/tmp/⟨tmp A⟩/log.txt, "a")10  file.puts extra_line(empty)11  file.close1213  lines→ ["first", "second", "bonus", "bonus", "bonus"] = File.read(path).split("\n")["first", "second", "bonus", "bonus", "bonus"]1415  puts "file=#{File.basename(path)log.txt}"16  puts "lines=#{lines.join(",")first,second,bonus,bonus,bonus}"17  puts "last=#{lines.lastbonus}"18end⋯outputfile=log.txt
lines=first,second,bonus,bonus,bonus
last=bonus
1extra_line ← done1require "tmpdir"23extra_line→ done = "done"45Dir.mktmpdir do |dir|6  path = File.join(dir, "log.txt")7  File.write(path, "first\nsecond\n")89  file = File.open(path, "a")10  file.puts extra_line11  file.close1213  lines = File.read(path).split("\n")1415  puts "file=#{File.basename(path)}"16  puts "lines=#{lines.join(",")}"17  puts "last=#{lines.last}"18end⋯
2path ← /tmp/⟨tmp A⟩/log.txt, file ← #<File:/tmp/⟨tmp A⟩/log.txt>⋯5Dir.mktmpdir do |dir/tmp/⟨tmp A⟩|6  path→ /tmp/⟨tmp A⟩/log.txt = File.join(dir, "log.txt")/tmp/⟨tmp A⟩/log.txt7  File.write(path/tmp/⟨tmp A⟩/log.txt, "first\nsecond\n")89  file→ #<File:/tmp/⟨tmp A⟩/log.txt> = File.open(path/tmp/⟨tmp A⟩/log.txt, "a")10  file.puts extra_line(empty)11  file.close1213  lines→ ["first", "second", "done", "done", "done"] = File.read(path).split("\n")["first", "second", "done", "done", "done"]1415  puts "file=#{File.basename(path)log.txt}"16  puts "lines=#{lines.join(",")first,second,done,done,done}"17  puts "last=#{lines.lastdone}"18end⋯outputfile=log.txt
lines=first,second,done,done,done
last=done