Hi, Something to be aware about when modifying the password file is that it should be locked to prevent another process from modifying it at the same time. There are different conventions on different systems for doing this and they depend also on the tool for modifying the password file.
For example, as far as I know the original BSD vipw utility creates an advisory lock named /etc/ptmp on BSD, Solaris and Linux systems. On some of these systems, it does also does postprocessing of the updated password file into dbm files. These days, however, useradd, usermod and userdel are the standard for updating /etc/password and they use a different locking convention on Linux vs Solaris. On linux, they create a lock file named /etc/password.lock that contains the PID of the locking process. On Solaris, the lock file is named /etc/.pwd.lock and is created by the lckpwdf(3C) basic C library function (see http://docs.sun.com/db/doc/816-0213/6m6ne3852?q=password+file+lock&a=vie w). One way to avoid having to remember these "trivialities" is to find a perl module in which they are all coded -- or at least mostly, so you only have to extend the existing framework or get the original author to do it :) So how can you find such a module? 1. In your web browser, surf to http://www.perl.com/pub/q/resources 2. In the list of resource categories, click on one that suits the problem. In this case the problem is system administration, so click on the Sysadmin link which takes you to http://www.perl.com/cs/user/query/q/6?id_topic=71 3. Scan the list of Sysadmin topics for something directly relevant to the problem. Presto, there is a module named Unix::ConfigFile near the bottom that includes a module named Unix::PasswdFile which does things with the password file. Clicking on the Unix::ConfigFile link takes you to http://www.perl.com/CPAN/modules/by-authors/id/S/SS/SSNODGRA/ from where you can download the latest sources and view the readme file. 4. Taking a look at the readme at http://www.perl.com/CPAN/modules/by-authors/id/S/SS/SSNODGRA/Unix-Config File-0.06.readme it says to run "perldoc Unix::PasswdFile" after installation to see the documentation, but let's find out now in the hope that someone has already put it up on the Internet. 5. Enter "perldoc Unix::PasswdFile" in the Google web search form at http://www.google.com and 7th down on the list of returned URLs is a link to "trustno1.net - perldoc" that redirects to http://perldoc.trustno1.net/new/index.html which contains the perldocs for a lot of modules including Unix::PasswdFile. 8. Click on the Unix::PasswdFile link to read its perldoc and find it contains a method named users( [SORTBY] ) that provides the means to sort /etc/password by UID and by username -- see http://perldoc.trustno1.net/new/site_perl/5.8.0/Unix/PasswdFile.html#use rs(_[sortby]_). And notice in the Description section of the Unix::PasswdFile perdoc it says that "it automatically handles file locking"! 9. If this is the functionality you want, then install Unix::ConfigFile from the CPAN link in (3). Probably you will find some working example perl programs in the distribution that you can simply modify to create your program. 10. If this is not the functionality you want, then you can use the source code of Unix::PasswdFile:users( SORTBY] ) to create a another method that sorts on the password field of your choice, or you can go back to (3) and (2) to find another module that better does what you need. 11. One of the great things about perl is the large community of programmers who have contributed opensource modules for a huge variety of applications so that you can almost always find one that you can either use directly to solve your problem at hand perhaps in combination with other modules, or you can use it's sources as the starting point for developing the precise program you need by extension and imitation. Now you know how to do the research to find existing perl solutions and starting points for the solutions of many problems! -tristram -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
