COMPUTER TALES

Learning unix operating system is very easy. It is just that you need to understand the unix server concepts and familiar with the unix commands. Here I am providing some important unix commands which will be used in daily work. Unix Commands With Examples: 1. Listing files The first thing after logging into the unix system, everyone does is listing the files in a directory. The ls command is used to list the files in a directory. >ls add.sh logfile.txt prime.pl If you simply execute ls on the command prompt, then it will display the files and directories in the current directory. >ls /usr/local/bin You can pass a directory as an argument to ls command. In this case, the ls command prints all the files and directories in the specific directory you have passed. 2. Displaying the contents of a file. The next thing is to display the contents of a file. The cat command is used to display the contents in a file. >cat file.txt This is a sample un...

Command and Usage Examples ATTRIB Change file attributes. '+' adds an attribute, '-' removes it. Attributes are: A=archive; R=read only; S=system; H=hidden. ATTRIB -R -A -S -H <VIRUS.EXE> All these attributes will be removed from virus.exe. C: Go to the C: drive. Similarly A: and D: etc. C: CD Change directory. When you change directory, the prompt changes, showing the path of the directory you are currently in. Note, directory is the term used by DOS for what Windows calls a folder. CD\ takes you to the top of the directory tree (typically to C:) . CD.. moves you one level up the directory tree (i.e. up towards the root directory). CD <DIRECTORYNAME> takes you to that directory. You can use one or more subdirectory names, separated by \ e.g. CD WINNT\Media takes you to the directory C:\WINNT\Media To change to another path, type the full path with slashes. e.g. CD \WINDOWS\SYSTEM CLS Clear the screen. CLS DEL Delete one or more...

Relationships:  One table (relation) may be linked with another in what is known as a  relationship.  Relationships may be built into the database structure to facilitate the operation of relational joins at runtime. A relationship is between two tables in what is known as a  one-to-many  or  parent-child  or  master-detail  relationship where an occurrence on the ‘one’ or ‘parent’ or ‘master’ table may have any number of associated occurrences on the ‘many’ or ‘child’ or ‘detail’ table. To achieve this, the  child  table must contain fields which link back the  primary key  on the  parent  table. These fields on the  child  table are known as a  foreign key,  and the  parent  table is referred to as the foreign table (from the viewpoint of the child). It is possible for a record on the  parent  table to exist without corresponding records on the  child  t...