Linux/Unix: vi/vim editing tips

How do I see line numbers ?

:set nu
:set nonu
does the opposite.

Indentation for formatting your programs/scripts

:set autoindent

Saving vi/vim preferences

You can create a file (a hidden file) by name .exrc and write all your ex commands one per line. You can copy-paste the following two lines as .exrc. These options/preferences will work next time you open vi.

set autoindent
set nu

Moving around quickly

* Last line - shift+g
* First line - gg
* One screen forward - ctrl+f
* One screen backward - ctrl+b
* Half screen forward (down) - ctrl+d
* Half screen backward (up) - ctrl+u
* 50th line - 50,shift+g
* Move forward a word - w
* Move back a word - b
* To start of line - 0
* To end of line - $
* Down a line - j
* Up a line - k
* One char left - h
* One char right - l

Deleting content

* Delete a character - x
* Delete a word - dw
* Delete a line - dd

You can multiply these commands with numbers ! e.g. ' 5dw' deletes 5 words.

Chaging content

* Change word - cw
* Change line - cc

Inserting content

You can go into insert mode by following ways

* Insert where cursor is - i
* From start of line - I (shift+i)
* Next line - o
* Previous line - O (shift+o)
* Next character - a
* End of line - A (shift+a)

Copying and pasting

The command to copy content is 'y' (yank).

* Copy a line - yy
* Copy a word - yw

Copy 5 lines - 5yy as explained above. Multiplication applies here as well.
Paste - p
Paste before the cursor position/previous line - P (shift+p)

Content from the last delete (cut) command is stored in a buffer by default. dd followed by p cuts current line and pastes it after the next line. Similarly, x followed by p swaps the chars of a word.

Saving and reading files

* :r filename - read file named filename and insert after current line (the line with cursor)
* :w - write current contents to file named in original vi call
* :w newfile - write current contents to a new file named newfile
* :12,35w smallfile - write the contents of the lines numbered 12 through 35 to a new file named smallfile
* :w! prevfile - write current contents over a pre-existing file named prevfile

Find and replace (substitutions)

This is normally done with ex editor command. Following is the syntax.
For replacing everywhere in the file,
:1,$s/pattern/replacement/g

Explanation

: indicates the start of an ex editor command
1,$ - from the first line to the last line. Alternatively, you can use % (for all lines of a file)
/ used to separate pattern and replacement. Here, you can use regular expressions.
g stands for all occurences of the pattern on a line

Linux/Unix: Environment variables

What are they ?

Environment variables are a set of dynamic values that can affect the way running processes will behave. All unix like operating systems as well as windows have their set of enviraonment variables. In unix like systems change in environment variable will affect only the child process run by that particular program or shell script which changes the environment.

Examples -

$PATH - shows the directories where shell looks for commands issued by a user
$HOME - shows where user's home directory is located on the file-system

env command shows all environment variables specific to your login.

Setting an environment variable

In bash, following two commands set up an environment variable called 'name'

> name=Ketan
> export name

To verify this, you can

> echo $name
or
> env | grep name

If you want a certain environment variable to be set when you login, keep the two commands in your .bashrc file.

Misc: why the name "Ketan's weekly"?

I intend to post something here on weekends. Rarely on weekdays :-)
Hope you find this blog useful.