How to use grep command to exclude the lines beginning with a pattern

For instance when reading from a file you want to exclude all the comments i.e. lines beginning with hash sign (#), then use -v switch for grep command:

grep -v "^\#" $FILENAME

Korn Shell scripting intro

I recently started writing korn shell scripts here and there and below is some useful info on how to get started. I use vi editor for creating files:

vi myscript.ksh

Korn shell scripts usually have extension ksh The first line of the script should always be:

#!/usr/bin/ksh

After the file has been created, one needs to give it execute permissions so that the file becomes runable:

chmod 755 myscript.ksh

Now the script can be executed as follows:

./myscript.ksh

if the script name or path has spaces in it, it needs to be wrapped in double quotes

"C:\My Documents\My Scripts\myscript.ksh"

The escape character for ksh scripts is a (\) backslash. For example if you want to escape a dollar sign ($) inside your script, instead of writing

select * from v$database;

use

select * from v\$database;

(#) pound sign is used for comments and print and echo commands are used to output text to a sceen

UNIX - clearing out files that are older than 30 days

Useful command for clearing out old files:

find ./* -type f -mtime +30 -exec rm {} \;

The above will clear out files that are older than 30 days in the current directory. find ./* will look at the current directory, grabbing all the files (*), -mtime +30 will specify files that are older than 30 days, and -exec rm {} \ will remove all the files that match the condition.

Some useful commands for vi Editor

Command	Action
x	delete one character
dw	delete current word
dd	delete current line
D	delete all content to the rigght of the cursor
:u	undo last command
:q	quit editor without saving
:wq	save and quit editor
:w	write without exit
:[n]	goto line [n]
b	move backwards one word
i	begin inserting text at the current cursor location