Monday, March 28, 2011

Shell Types in Unix

Just like people know different languages and dialects, your UNIX system will usually offer a variety of shell types:
sh or Bourne Shell: the original shell still used on UNIX systems and in UNIX-related environments. This is the basic shell, a small program with few features. While this is not the standard shell, it is still available on every Linux system for compatibility with UNIX programs.

bash or Bourne Again shell: the standard GNU shell, intuitive and flexible. Probably most advisable for beginning users while being at the same time a powerful tool for the advanced and professional user. On Linux, bash is the standard shell for common users. This shell is a so-called superset of the Bourne shell, a set of add-ons and plug-ins. This means that the Bourne Again shell is compatible with the Bourne shell: commands that work in sh, also work in bash. However, the reverse is not always the case. All examples and exercises in this book use bash.

csh or C shell: the syntax of this shell resembles that of the C programming language. Sometimes asked for by programmers.

tcsh or TENEX C shell: a superset of the common C shell, enhancing user-friendliness and speed. That is why some also call it the Turbo C shell.

ksh or the Korn shell: sometimes appreciated by people with a UNIX background. A superset of the Bourne shell; with standard configuration a nightmare for beginning users.
The file 
/etc/shells gives an overview of known shells on a Linux/Unix system:

mia:~> cat /etc/shells

Your default shell is set in the /etc/passwd file, like this line for user pertsch:

pertsch:L2NOfqdlPrHwE:504:504:pertsch Maya:/home/pertsch:/bin/bash

To switch from one shell to another, just enter the name of the new shell in the active terminal. The system finds the directory where the name occurs using the PATH settings, and since a shell is an executable file (program), the current shell activates it and it gets executed. A new prompt is usually shown, because each shell has its typical appearance:

pertsch:~> tcsh


Friday, March 25, 2011

Start Fight against the aging after your college

College is the days where we will have our young days. College is the days where we will spend our young days. People can see the young faces in college. Our faces will look brighter in the young age. When we finished our college days, we have to go for a job. To get a job, we have to attend more number of interviews. We have to roam a lot in the sunlight to get a job. From that our aging problem starts. Our skins will dry when we are roaming. Its because of the harmful rays in the sunlight, dust and pollution. With all these problem we will look aged people in the young age itself. It's because our skin becomes dry when we roam outside. Start your anti-aging skin care once you finish the college. You can take the treatment for aging problem as well as you can use the anti-aging skin care products. With the skin-care products and treatment you will look young even at the old age. With this kind of treatments, you will look 28 to30 when you are at the age of 40 to 45. Do the treatment of anti-aging and look young even at your old age.