Reading lines in the text file which is growing and may be rotated, such as unix system log file.
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README.md

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:

dependencies:
  logreader:
    github: arcage/crystal-logreader

Usage

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 that no data read, 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.

Contributors

  • arcage ʕ·ᴥ·ʔAKJ - creator, maintainer