Monday, February 4, 2013

How to enter password by linux command?

Q. As the title.I would like to find out How to enter password by linux command?

eg: when you write a script to sudo root. then you will be asked to enter password.
how can i do it by linux script? Is there a command can do the job?
Thanks in advance.

A. Don't. just run sudo script instead of trying to put sudo into the script.

Is there a way to reset the stats for the Linux command df?
Q. For a while now whenever I use the command df in Linux it shows that one of my partitions is full but if I use the du -ac command it shows that I am using only 4.2 of 7.8 Gigs of storage. Is there a way to reset the stats for the Linux command df?

A. Df and du do not measure the same exact things. You can google for: df VS du and see a lot of explanations.

Where do I find source code of linux commands?
Q. Linux commands like cp, dir, ls, shred, man (etc...) are nothing but programs (hopefully all written in C). I would really like to know exactly how they work (and make a few modifications to some) so I need their source code...
Can you tell me where to find source code of linux commands?
Thank you in advance!

A. In general there are several places you can go to get the source for these commands. This is mostly because there can be several different implementations of the commands.

1) The company who distributed your version of Linux. Most versions of these types of commands are under the GPL and as such the person or company who gave you the executable has to make a copy of the source code available to you. Usually these are released as source rpms, and some times come on one of the CDs or DVDs that you used to install Linux with. You can often find them on the web too.

For example the RHEL5 Server source rpm (SRPM) is
ftp://ftp.redhat.com/pub/redhat/linux/enterprise/5Server/en/os/SRPMS/coreutils-5.97-12.1.el5.src.rpm

Most of the time your distribution will have a tool like yum to install these and other rpms for you.

2) www.gnu.org
GNU probably wrote the commands that are on your distribution of Linux, although a few very specialized distros use different implementations of the commands (Usually busybox http://www.busybox.net/ but this is really rare).

http://www.gnu.org/software/coreutils/
has instructions on how to download a very recent copy of the code, which may be much much newer then the version currently installed on your computer.

NOTE:

Some shells, like tcsh and csh have their own implementations of these commands built into them. This is because it is faster to run the command as part of your shell then to fork and exec a new command. So if you do change them be sure to check that you are actually running your updated version. BASH usually does not play these games but you can always check by running which followed by the name of your command.



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