On Tue, 11 Feb 2003 16:35:28 -0800, David wrote: > Madhu Reddy wrote: > >> I want to sort a file and want to write the result >> to same file.... >> I want to sort a based on 3rd column.. >> ... >> file may have around 20 millions rows ...... >> > > if you are using the *nix os, you should try the sort utility. if you are > not using *nix and you don't have the sort utility, you will have to rely > on Perl's sort function. with 20m rows, you probably don't want to store > everything in memory and then sort them. what you have to do is sort the > data file segment by segment and then merge them back. merging is the real > tricky business. the following script(which i did for someone a while ago) > will do that for you. what it does is break the file into multiple chunks of > 100000 lines, sort the chunks in a disk tmp file and then merge all the > chunks back together. when i sort the file, i keep the smallest boundary of > each chunk and use this number to sort the file so you don't have to > compare all the tmp files.
Absolute right, allthough I wouldn't write it for my own. A merge sort is implemented as command line tool by the Perl Power Tools, available as PPT in CPAN. Greetings, Janek -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
