first commit

.gitignore

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+/doc/
+/libs/
+/lib/
+/.crystal/
+/.shards/
+/test/
+
+# Libraries don't need dependency lock
+# Dependencies will be locked in application that uses them
+/shard.lock

.travis.yml

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+language: crystal

LICENSE

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+The MIT License (MIT)
+
+Copyright (c) 2016 ʕ·ᴥ·ʔAKJ
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

README.md

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+# LogReader
+
+Reading lines in the text file which is growing and may be rotated, such as unix system log file.
+
+* When the current file reaches EOF, this will wait new line added to the file. (like `tail -f` command)
+* Even when the current file is rotated, this will trace new file and continue reading lines.
+
+## Installation
+
+Add this to your application's `shard.yml`:
+
+```yaml
+dependencies:
+  logchaser:
+    github: arcage/crystal-logreader
+```
+
+## Usage
+
+```crystal
+require "logreader"
+
+# create LogReader object
+log = LogReader.new("/var/log/maillog")
+
+# reads single line from the file
+# waits new line, when the file reaches EOF
+puts log.read_line
+
+# iterates each line in the file
+log.each do |line|
+  puts line
+end
+```
+
+`LogReader` has only two public instance method `#read_line` and `#each`
+
+`#each` will not finish in normal operation. if you want to stop it, you have to do it forcibly by using `Ctrl+C`, `kill` command etc.
+
+### Internal behaviour
+
+When reading no data for reasons such as EOF, `LogReader` try to read more data every second.
+
+For every consecutive 5 results of reading are no data, `LogReader` checks whether or not the inode number associated with the file name was changed.
+
+If it had been changed, `LogReader` close current file and re-open the file.
+
+## Contributing
+
+1. Fork it ( https://github.com/[your-github-name]/logchaser/fork )
+2. Create your feature branch (git checkout -b my-new-feature)
+3. Commit your changes (git commit -am 'Add some feature')
+4. Push to the branch (git push origin my-new-feature)
+5. Create a new Pull Request
+
+## Contributors
+
+- [arcage](https://github.com/arcage) ʕ·ᴥ·ʔAKJ - creator, maintainer

shard.yml

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+name: logchaser
+version: 0.1.0
+
+authors:
+  - ʕ·ᴥ·ʔAKJ <arcage@denchu.org>
+
+license: MIT

spec/logreader_spec.cr

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+require "./spec_helper"
+
+describe LogReader do
+  # TODO: Write tests
+
+  it "works" do
+    false.should eq(true)
+  end
+end

spec/spec_helper.cr

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+require "spec"
+require "../src/logreader"

src/logreader.cr

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+require "./logreader/*"
+
+class LogReader
+  class Error < Exception; end
+
+  @path : String
+  @file : File
+
+  def initialize(path : String)
+    @path = File.expand_path(path)
+    @file = open_file
+  end
+
+  def each
+    loop do
+      yield read_line
+    end
+  end
+
+  def read_line : String
+    eof_count = 0
+    not_exist = false
+    String.build do |str|
+      loop do
+        if char = @file.read_char
+          str << char
+          break if char == '\n'
+          p eof_count = 0
+          p not_exist = false
+        elsif eof_count < 5
+          sleep(1)
+          p eof_count += 1
+        else
+          begin
+            @file = reopen_file if File.stat(@path).ino != ino
+          rescue err : Errno
+            if err.errno != Errno::ENOENT || not_exist
+              raise err
+            else
+              p not_exist = true
+            end
+          ensure
+            p eof_count = 0
+          end
+        end
+      end
+    end
+  end
+
+  private def ino
+    @file.stat.ino
+  end
+
+  private def reopen_file : File
+    @file.close unless @file.closed?
+    open_file
+  end
+
+  private def open_file : File
+    raise Error.new("#{@path} is not a readable file.") unless File.file?(@path) && File.readable?(@path)
+    File.open(@path)
+  end
+end

src/logreader/version.cr

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+class LogReader
+  VERSION = "0.1.0"
+end