Clean up and simplify the DSL

Use instance_eval instead of eval'd code blocks
to implement the filter and execution blocks

Kudos to https://github.com/edjames for the
suggestion!

Author: pvdb

README.md

@@ -60,44 +60,44 @@ Advanced Examples
 
 * read from STDIN and print out the length of each line _(to illustrate -e option)_
 
-        $ ntail -e '{ |line| puts line.size }'
+        $ ntail -e 'puts size'
 
 * read from STDIN but only print out non-empty lines _(to illustrate -f option)_
 
-        $ ntail -f '{ |line| line.size $ 0 }'
+        $ ntail -f 'size != 0'
 
 * the following invocations behave exactly the same _(to illustrate -e and -f options)_
 
         $ ntail
-        $ ntail -f '{ |line| true }' -e '{ |line| puts line }'
+        $ ntail -f 'true' -e 'puts self'
 
 * print out all HTTP requests that are coming from a given IP address
 
-        $ ntail -f '{ |line| line.remote_address == "208.67.222.222" }' /var/log/nginx/access.log
+        $ ntail -f 'remote_address == "208.67.222.222"' /var/log/nginx/access.log
 
 * find all HTTP requests that resulted in a '5xx' HTTP error/status code _(e.g. Rails 500 errors)_
 
-        $ gunzip -S .gz -c access.log-20101216.gz | ntail -f '{ |line| line.server_error_status? }'
+        $ gunzip -S .gz -c access.log-20101216.gz | ntail -f 'server_error_status?'
 
 * generate a summary report of HTTP status codes, for all non-200 HTTP requests
 
-        $ ntail -f '{ |line| line.status != "200" }' -e '{ |line| puts line.status }' access.log | sort | uniq -c
+        $ ntail -f 'status != "200"' -e 'puts status' access.log | sort | uniq -c
         76 301
         16 302
          2 304
          1 406
 
 * print out GeoIP country and city information for each HTTP request _(depends on the optional `geoip` gem)_
 
-        $ ntail -e '{ |line| puts [line.to_country_s, line.to_city_s].join("\t") }' /var/log/nginx/access.log
+        $ ntail -e 'puts [to_country_s, to_city_s].join("\t")' /var/log/nginx/access.log
         United States   Los Angeles
         United States   Houston
         Germany         Berlin
         United Kingdom  London
 
 * print out the IP address and the corresponding host name for each HTTP request _(slows things down considerably, due to `nslookup` call)_
 
-        $ ntail -e '{ |line| puts [line.remote_address, line.to_host_name].join("\t") }' /var/log/nginx/access.log
+        $ ntail -e 'puts [remote_address, to_host_s].join("\t")' /var/log/nginx/access.log
         66.249.72.196   crawl-66-249-72-196.googlebot.com
         67.192.120.134  s402.pingdom.com
         75.31.109.144   adsl-75-31-109-144.dsl.irvnca.sbcglobal.net

lib/ntail/application.rb

@@ -54,10 +54,10 @@ def run!
               if log_line.parsable
                 parsable_lines += 1
                 unless @options.parse_only
-                  if !@options.filter || @options.filter.call(log_line)
+                  if !@options.filter || log_line.instance_eval(@options.filter)
                     lines_processed += 1
                     if @options.code
-                      @options.code.call(log_line)
+                      log_line.instance_eval(@options.code)
                     else
                       puts log_line.to_s(:color => true)
                     end

lib/ntail/options.rb

@@ -16,11 +16,11 @@ def parse_options(argv, defaults = {})
         end
 
         opts.on '--filter',  '-f CODE', "Ruby code block for filtering (parsed) lines - needs to return true or false." do |value|
-          options.filter = eval "Proc.new #{value}"
+          options.filter = value
         end
 
         opts.on '--execute',  '-e CODE', "Ruby code block for processing each (parsed) line." do |value|
-          options.code = eval "Proc.new #{value}"
+          options.code = value
         end
 
         opts.on '--line-number', '-l LINE_NUMBER', "Only process the line with the given line number" do |value|