Tips and Tricks

If you saw a lot of ^M character in your code, reason being is ^M is the character in DOS if you create the file in Windows.

If you transfer the DOS file into unix, you will see lots of ^M in your file and it is very irritating indeed.

You can do a simple magic in vi by

:%s/[crtl-v ctrl-m//g

meaning,
%s - substitute
[ctrl-v ctrl-m] - create the ^M character
// - empty
g - replace globally

How to use regular expression (regex) in grep or vi?

If you need to search for a pattern of "string" or "character" in a file / many files, you will need to use regular expression (regex) either in vi editor or in grep command. But how? See below:

using vi:
- press '/' for searching
- for instance, i wanted to search for CL000, CL001, CL002, ie: the pattern is CLXXX follow by digit.
- syntax:
/^CL[0-9]*

^ - start of pattern
* - zero or more digit

using unix grep command:
- grep CL[0-9]