On Tue, 2008-01-29 at 18:17 -0800, Nelson Serafica wrote: > I need to create a script where if there are new alias created, it > will dump to a file called address.txt.
ok, i don't do that, so i don't know enough details to discuss the specific problem. > Can diff recognize the new added text and removed text? however, *this* i do know about. when you run diff with two filenames (previous and current) it'll show the differences. the lines that start with a greater than sign (>) indicate that the line is in the file on the right (e.g., if you do: diff old_file.txt new_file.txt then lines that start with > mean that the line was ADDED in the new file. it wasn't in the old file. similarly, lines that start with < mean that the line was in the old file and was removed in the new file. changes are a little tricky. youll have a < and a > one after the other and you need to notice that the two lines have essentially the same data with some data changed. e.g., < tiger was here > tiger wasn't here indicates that the line was changed (n't) inserted. diff can get confused if the file is very large and a line was moved from one part of the file to another part. for something like /etc/aliases though, where order doesn't matter, what you could do is sort the files before doing the diff (or sort the new file, since the old file would have already been sorted in the previous run). that can help diff a bit. > Or do I need to use other language? Or there are other commands > similar to diff? I tried a create script as simple as possible that's > why I'm using bash. for something similar (but much more complex) i've done: A. store the versions in version control (svn) and then just svn commit in cron. if there are no differences, the commit won't do anything. this can get a little tricky if you get conflicts though. you probably won't with /etc/alias since there won't be multi row records and you'll sort. but in the past, when there was a conflict the script would detect that and then just automatically use the latest file and resolve. the advantage of this is, you don't need to worry about file renames, atomicity, etc. tiger _________________________________________________ Philippine Linux Users' Group (PLUG) Mailing List [email protected] (#PLUG @ irc.free.net.ph) Read the Guidelines: http://linux.org.ph/lists Searchable Archives: http://archives.free.net.ph
