{"id":164,"date":"2009-04-23T21:05:34","date_gmt":"2009-04-23T20:05:34","guid":{"rendered":"http:\/\/pgregg.com\/wp\/?p=164"},"modified":"2009-04-23T21:05:34","modified_gmt":"2009-04-23T20:05:34","slug":"tail-file-in-php","status":"publish","type":"post","link":"https:\/\/blog.pgregg.com\/blog\/2009\/04\/tail-file-in-php\/","title":{"rendered":"tail -# file, in PHP"},"content":{"rendered":"

I read Kevin’s Read Line from File<\/a> article today and thought I would add some sample code I wrote a while back to address a similar task in PHP – How to perform the equivalent of “tail -# filename” in PHP.<\/p>\n

A typical task in some applications such as a shoutbox or a simple log file viewer is how to extract the last ‘n’ lines from a (very) large file – efficiently.\u00a0 There are several approaches one can take to solving the problem (as always in programming there are many ways to skin the proverbial cat) – taking the easy way out and shelling out to run the tail command; or reading the file line by line keeping the last ‘n’ lines in memory with a queue.<\/p>\n

However, here I will demonstrate a fairly tuned method of seeking to the end of the file and stepping back to read sufficient lines to the end of the file. If insufficient lines are returned, it incrementally looks back further in the file until it either can look no further, or sufficient lines are returned.<\/p>\n

Assumptions need to be made in order to tune the algorithm for the competing challenges of :<\/p>\n