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File manipulation utility methods


Though Ruby's File and FileUtils libraries provide very robust apis for dealing with files, this library aims to provide a level of abstraction that is much more convenient, with useful logging capabilities.


Add this line to your application's Gemfile:

gem "tty-file"

And then execute:

$ bundle

Or install it yourself as:

$ gem install tty-file


1. Usage

TTY::File.replace_in_file("Gemfile", /gem 'rails'/, "gem 'hanami'")

2. Interface

The following methods are available for creating and manipulating files.

If you wish to silence verbose output use verbose: false. Similarly if you wish to run action without actually triggering any action use noop: true.

2.1. binary?

To check whether a file is a binary file, i.e. image, executable etc. do:

TTY::File.binary?("image.png") # => true

2.2. checksum_file

To generate a checksum for a file, IO object, or String, use checksum_file. By default the MD5 algorithm is used, which can be changed by passing a second argument.

Among the supported message digest algorithms are:

  • sha, sha1, sha224, sha256, sha384, sha512
  • md2, md4, md5

For example, to create a digest for a string using SHA1 do:

TTY::File.checksum_file("Some content\nThe end", "sha1")
# => "289388f187404135e6c15b21460442cf867180dd"

2.3. chmod

To change file modes use chmod, like so:

TTY::File.chmod("filename.rb", 0777)

There are a number of constants available to represent common mode bits such as TTY::File::U_R and TTY::File::O_X, and they can be used as follows:

TTY::File.chmod("filename.rb", TTY::File::U_R | TTY::File::O_X)

Apart from traditional octal number definition for file permissions, you can use the more convenient permission notation used by the Unix chmod command:

TTY::File.chmod("filename.rb", "u=wrx,g+x")

The u, g, and o specify the user, group, and other parts of the mode bits. The a symbol is equivalent to ugo.

2.4. copy_file

Copies a file's contents from a relative source to a relative destination.

TTY::File.copy_file "Gemfile", "Gemfile.bak"

If you provide a block then the file content is yielded:

TTY::File.copy_file("Gemfile", "app/Gemfile") do |content|
  "\n" + content

If the source file is an ERB template then you can provide a :context in which the file gets evaluated, or if TTY::File gets included as a module then appropriate object context will be used by default. To use :context do:

variables =
variables[:foo] = "bar"

TTY::File.copy_file("templates/application.html.erb", context: variables)

You can also specify the template name surrounding any dynamic variables with % to be evaluated:

variables =
variables[:file_name] = "foo"

TTY::File.copy_file("templates/%file_name%.rb", context: variables)
# => Creates templates/foo.rb

If the destination is a directory, then copies source inside that directory.

TTY::File.copy_file "docs/", "app"

If the destination file already exists, a prompt menu will be displayed to enquire about action:

If you wish to preserve original owner, group, permission and modified time use :preserve option:

TTY::File.copy_file "docs/", "app", preserve: true

2.5. create_file

To create a file at a given destination with some content use create_file:

TTY::File.create_file "file-a/", content

On collision with already existing file, a menu gets displayed:

   collision  examples/file-a
Overwrite examples/file-a? (enter "h" for help) [y,d,n,q,h]

The d option allows to compare the changes:

--- a/examples/file-a
+++ b/examples/file-a
@@ -1,8 +1,9 @@
Overwrite examples/file-a? (enter "h" for help) [y,d,n,q,h]

You can force to always overwrite file with :force option or always skip by providing :skip.

There is examples/overwrite.rb that demonstrates diffing file with new content.

2.6. copy_dir

To recursively copy a directory of files from source to destination location use copy_directory or its alias copy_dir.

Assuming you have the following directory structure:

# doc/
#   subcommands/
#     command.rb.erb
#   %name%.rb

You can copy doc folder to docs by invoking:

TTY::File.copy_directory("doc", "docs", context: ...)

The context needs to respond to name message and given it returns foo value the following directory gets created:

# docs/
#   subcommands/
#     command.rb
#   foo.rb

If you only need to copy top level files use option recursive: false:

TTY::File.copy_directory("doc", "docs", recursive: false)

By passing :exclude option you can instruct the method to ignore any files including the given pattern:

TTY::File.copy_directory("doc", "docs", exclude: "subcommands")

2.7. create_dir

To create directory use create_directory or its alias create_dir passing as a first argument file path:


Or a data structure describing the directory tree including any files with or without content:

tree =
  "app" => [
    ["Gemfile", "gem 'tty-file'"],
    "lib" => [
      ["file_utils.rb", "require 'tty-file'"]
    "spec" => []
# =>
# app
# app/
# app/Gemfile
# app/lib
# app/lib/cli.rb
# app/lib/file_utils.rb
# app/spec

As a second argument you can provide a parent directory, otherwise current directory will be assumed:

TTY::File.create_dir(tree, "/path/to/parent/dir")

2.8. diff_files

To compare files line by line in a system independent way use diff, or diff_files:

print TTY::File.diff_files("file-a", "file-b")

Printing output to console would result in:

        diff  examples/file-a and examples/file-b
--- examples/file-a
+++ examples/file-b
@@ -1,8 +1,9 @@

You can also pass additional parameters such as:

  • :format - accepted values are :unified, :old, :context and :ed. Defaults to :unified as seen in the output above - similar to git tool.
  • :lines - how many extra lines to include in the output around the compared lines. Defaults to 3 lines.
  • :threshold - set maximum file size in bytes. By default files larger than 10Mb are no processed.
  • :header - controls display of two-line files comparison. By default true.

Changing format to :old, removing context lines and skipping log output:

TTY::File.diff_files("file_a", "file_b", format: :old, lines: 0, verbose: false)

Results in the following output:

<<< examples/file-a
>>> examples/file-b
< ccccc
> xxxxx

< ggggg
> yyyyy

In addition, you can perform a comparison between a file and a string or between two strings. For example, comparing file with content:

TTY::File.diff_files("file-a", "new\nlong\ntext")

Will output:

        diff  a/examples/file-a and b/examples/file-a
--- a/examples/file-a
+++ b/examples/file-a
@@ -1,8 +1,4 @@

Please run examples/diff.rb to see how output works.

2.9. download_file

To download a content from a given address and to save at a given relative location do:

TTY::File.download_file("", "doc/")

If you pass a block then the content will be yielded to allow modification:

TTY::File.download_file("", "doc/") do |content|
  content.gsub("\n", " ")

By default download_file will follow maximum 3 redirects. This can be changed by passing :limit option:

TTY::File.download_file("", "doc/", limit: 5)
# => raises TTY::File::DownloadError

2.10. inject_into_file

Inject content into a file at a given location and return true when performed successfully, false otherwise.

TTY::File.inject_into_file "filename.rb", "text to add", after: "Code below this line\n"

Or using a block:

TTY::File.inject_into_file "filename.rb", after: "Code below this line\n" do
  "text to add"

You can also use Regular Expressions in :after or :before to match file location.

By default, this method will always inject content into file, regardless whether it is already present or not. To change this pass :force set to false to perform check before actually inserting text:

TTY::File.inject_into_file("filename.rb", "text to add", after: "Code below this line\n"

Alternatively, use safe_inject_into_file to check if the text can be safely inserted.

TTY::File.safe_inject_into_file("Gemfile", "gem 'tty'")

The append_to_file and prepend_to_file allow you to add content at the end and the begging of a file.

2.11. replace_in_file

Replace content of a file matching condition by calling replace_in_file or gsub_file, which returns true when substitutions are performed successfully, false otherwise.

TTY::File.replace_in_file "filename.rb", /matching condition/, "replacement"

The replacement content can be provided in a block

TTY::File.gsub_file "filename.rb", /matching condition/ do

2.12. append_to_file

Appends text to a file and returns true when performed successfully, false otherwise. You can provide the text as a second argument:

TTY::File.append_to_file("Gemfile", "gem 'tty'")

Or inside a block:

TTY::File.append_to_file("Gemfile") do
  "gem 'tty'"

By default, this method will always append content regardless whether it is already present or not. To change this pass :force set to false to perform check before actually appending:

TTY::File.append_to_file("Gemfile", "gem 'tty'", force: false)

Alternatively, use safe_append_to_file to check if the text can be safely appended.

TTY::File.safe_append_to_file("Gemfile", "gem 'tty'")

2.13. prepend_to_file

Prepends text to a file and returns true when performed successfully, false otherwise. You can provide the text as a second argument:

TTY::File.prepend_to_file("Gemfile", "gem 'tty'")

Or inside a block:

TTY::File.prepend_to_file("Gemfile") do
  "gem 'tty'"

By default, this method will always prepend content regardless whether it is already present or not. To change this pass :force set to false to perform check before actually prepending:

TTY::File.prepend_to_file("Gemfile", "gem 'tty'", force: false)

Alternatively, use safe_prepend_to_file to check if the text can be safely appended.

TTY::File.safe_prepend_to_file("Gemfile", "gem 'tty'")

2.14. remove_file

To remove a file do:

TTY::File.remove_file "doc/"

You can also pass in :force to remove file ignoring any errors:

TTY::File.remove_file "doc/", force: true

2.15. tail_file

To read the last 10 lines from a file do:

TTY::File.tail_file "doc/"
# => ["## Copyright", "Copyright (c) 2016-2017", ...]

You can also pass a block:

TTY::File.tail_file("doc/") do |line|
  puts line

To change how many lines are read pass a second argument:

TTY::File.tail_file("doc/", 15)


After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to


Bug reports and pull requests are welcome on GitHub at This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.


The gem is available as open source under the terms of the MIT License.

Copyright (c) 2016 Piotr Murach. See LICENSE for further details.