How to convert lower-case to upper-case in C++ ?

Standard C library does not provide any built-in function to convert lower case to upper case and vice versa.
C++ STL has an elegant and simple solution for this : transform function.

Note : include the algorithm header file in your C++ file.

To convert Upper Case -> Lower Case:
transform( upperLine.begin(),upperLine.end(), upperLine.begin(),(int(*)(int)) tolower );

To convert Lower Case -> UpperCase:
transform( lowerLine.begin(),lowerLine.end(), lowerLine.begin(),(int(*)(int)) toupper );

Cheers

How to use the OR operator in Grep?

Ever wondered how to search for multiple patterns in one grep statement? One problem I often come across is, while using grep, if I want to search for something like “find all matches that start with a $ or with #“, I am stuck.

Well apparently using the OR operator in grep is trivial.

grep “^$\|^#” foo.dat ( this will return all matches that start with a $ or with # )

Note: Do NOT forget the backslash \ before the |.

Hope that will help someone

How to tar and untar files in UNIX?

Few years ago, during my undergraduate degree, I was asked to compress my assignment using tar and submit it. I was so scared with all the tar+compress+unix jig, that I ended up NOT submitting the assignment :O. Now when I look back, I feel so stupid. Anyways, now that I know a lil bit more about tar and untar, I’d like to share my knowledge with everyone and hopefully help someone from NOT submitting an assignment

Basically tar can be used to group multiple files/directories into one single file, and separate(extract) an archive created by tar into separate files.

* To group multiple files : tar -cvf foo.tar a.dat b.dat c.dat ( this will group files [a-c]*.dat to one file foo.tar )
c = create a tar file
v = verbose( nothing important )
f = create the tar file with filename provided as the argument

Thats all you need to know to tar(group) a bunch of files/directories.

* To tar files and gzip them : tar -czf foo.tar.gz *.dat ( this will create a gzip-compressed Tar file of the name foo.tar.gz of all files with a .dat suffix in that directory )

* To untar(separate) files from a tar archive : tar -xvf foo.tar ( this will produce three separate files a.dat, b.dat and c.dat )

* To untar(extract) a gzipped tar archive file : tar -xzf foo.tar.gz

* To untar a bzipped (.bz2) tar archive file : tar -xjf foo.tar.bz2

How To Flush/Clear Squid Cache

Squid is a high-performance proxy caching server for web clients, supporting FTP, gopher, and HTTP data objects. Unlike traditional caching software, squid handles all requests in a single, non-blocking, I/O-driven process.

Sometimes we need to clear the contents in the cache and restart the program. Clearing the squid cache is brain simple:

goto the directory where the squid program resides( e.g. /etc/init.d/ )
./squid flush

You would need root(su) priviledges to perform the operation

Reference :
Squid Cache

Going Back To School …

I am going back to school tomorrow after a break of 14 months. I am feeling like a bundle of nerves (happy+nervous+skeptical+sad+…) right now. I have not been allowed to do a thesis for my Masters, and the only way I can switch is, if i get straight A’s in the first four courses. Obviously that is no easy task, in fact it will be insanely tough. But as Randy Pausch so aptly said: “Brick Walls are there for a reason…it shows us,how badly we want something”. So here I am, fighting against brick wall odds, to prove to the world I am good enough.

I feel like an old, aged warrior, preparing for one last battle, one last shot at glory…