Encrypt files using Vim

Vim comes with default encryption mechanism refereed as VimCrypt in the documentation. It is capable of writing files encrypted and read them back.

Creating new encrypted file:

vim -x <file>

This will create new file if it is not exist or open an existing file and prompt for password. This password is used as key to encrypt and decrypt the file.

Encrypt the current working file:

:X

You can also encrypt the current working file /open files using :X  option. This will also prompt for password. The typed password is stored in the 'key' option which is used to encrypt the file when it is written.

Disable the encryption:

To disable the encryption reset the 'key' option to empty value. To do this you first need to open the file with proper password.

:set key=

Read More

Automate your Vim - The power of autocmd

1. Vim templates

I often used to write sample C++ codes to test the functionality. But it is pain to add default code for every test code that I write. Vim has a brilliant solution for it. that is templates.

Create some template files in any of the directory you wish, here I created ~/.vim/templates/skeleton.cpp that contains default c++ code i.e #include, using namespace std, main,..etc.
Then add the below code to your ~/.vimrc  file. Now try to open a new cpp file and see the magic.


Here we are telling vim that, if I try to open a new cpp file, read the content from ~/.vim/templates/skeleton.cpp file and write to the new file that is opened. Similarly you can have templates for all type of files.

This means, what ever you write in template will be loaded by default for every file you open newly using vim.

2. Auto compile C++ code on saving

We can even compile the code immediately after saving the file without typing any single command.  Add the below code to your vimrc file and try to save the test cpp file. It will create a executable with the name of the file.

1 2	"Auto compile on save autocmd BufWritePost,FileWritePost *.cpp !g++ -Wall %:p -o %:r

In vim :p expands to full file name path and :r expands to root of the file name (file extension will be removed)

But this is bad ! every time you try to save your file it tries to compile. So there is alternative, vim has quit event. i.e VimLeave.

1 2	"auto compile on quit - silent: do not report errors autocmd VimLeave *.cpp !silent g++ -Wall %:p -o %:r

VimLeave event indicates vim to execute the command specified after ! before exiting the vim after writing viminfo file.

3. Abbreviations for faster coding

Abbreviations can save typing when you want to type same text multiple times thorough the document. and abbreviations can be defined to auto correct the typos.
Add the below code to your vimrc file and try to edit the cpp file. when every you type iff this will be auto corrected to if ()  and moves the cursor in between the parenthesis.


abbrev(ab) is used to create abbreviations, this works on normal mode. iabbrev is used to work with abbreviations on insert mode. and <left> is used to move the cursor one character left.

4. Auto comments

Similarly to automate commenting add the below code to vimrc.


Vim will detect the file type using FileType event. And we are mapping the movement ,c to comment lines.
But this will comment only current line.

For commenting a block of text, go to the first line you want to comment, press Ctrl + V, and select until the last line. Second, press I// + Esc (then give it a second), and it will insert a // character on all selected lines.

ctrl+v
drop down using arrow key(select only first character of the each line)
shif+i
shift+//
esc

Un-commenting a block of text is almost the same: Put your cursor on the first # character, press CtrlV and go down until the last commented line and press x, that will delete all the # characters vertically.

Learning from http://learnvimscriptthehardway.stevelosh.com/

Read More

A Bit Close Look At Vi - More On 'registers'

Note - read Marks & Registers before reading this post.

There are some other ways of copy or delete text in vi.

Working with paragraphs:

If you are in paragraph text you can use  }  and  {  to move  cursor to the beginning or ending of the paragraph respectively.  so if you want to move a paragraph you can use  {  and  d} . 
and   p  to paste the content.  if you are already in beginning or ending of a paragraph you can use   d}  and  d{  respectively to cut the paragraph.
If you want to delete 3 continuous paragraphs you can use  d3} (From current to next 3 paragraphs will be cut) 
And if you want to move multiple paragraphs from multiple locations to other locations we can make use of registers ( Marks & Registers ).

Ex:
I am at para 1: hit   "ad3}  to cut 3 paragraphs  to the register 'a'
I am at para 9: hit   "by}  to copy next paragraph to the register 'b' 
At EOF: hit  "ap  and  "bp   to paste the paragraphs.

Copy/Cut by Search:

Search using  /  or  ?  is most notable technique in vi. But if you want to copy the content from current line to the next line containing a specific word ??.
for example one can use  y/foo  to copy the text from current line to next line containing the word 'foo'. similarly 'd' can be used to cut ( d/foo).
y?foo to copy from the current line to the most recent (previous) line containing 'bar'.

Similarly as above we can use registers to copy/cut these content.
Thus if you use "ay/foo then you are yanking a copy of the text from here to the next line containing "foo" into the 'a' register. and can use   "ap  to paste the content.

Read More

Vi - Marks and Registers

Marks:

vi has 26 "marks". A mark is set to any cursor location using the m command. 
Each mark is designated by a letter. 
Thusma sets the 'a' mark to the current location, andms sets the 's' mark. 
 You can move to the line containing a mark using the ' (single quote) command. 
 Thus 'a moves to the beginning of the line containing the 'a' mark. 
 You can move to the precise location of any mark using the ` (backquote) command. 
 Thus `s will move directly to the exact location of the 's' mark.

copy/cut/paste :

One can use d,y,p to delete,yank,paste respectively. 
step 1 : set the mark by using m
step 2 : y'a to copy from current position to line where mark a is set.
             y`a to copy from current position to exact location of mark a.
             [ 'd' can be used similarly ]
step 3 : use p to paste the content.

To access all currently defined markers hit :makrs

some other interesting features are there in vi where we can use marks.

# for example if you want to sort a set of lines in vi what you do ?? There is a simple solution for it.
place two marks on two lines. and then you you hit :'a,'b!sort ( ! will execute shell commands on vi)

# if you want to redirect a part of file to another file
place two marks on two lines and then :'a,'b w temp_file. this will copy the content from mark a to b to the new temp_file. if file already exist use :'a,'b w>>temp_file to append.
  
Note: a-z can be used to mark only in same file. use A-Z to mark across the files.. So now copy a line from one file to other file is much more easier !! 

Registers:

vi has 26 "registers". we can use these registers by prefixing  " (double quote)Each register is designated by a letter.
Thus"a starts the register. now its up to you to use this register to copy the content to it or cut the content to it or paste the content from it.

This is more useful when you want to copy lines from multiple locations and paste it in different places.

copy/cut/paste :
Ex:

I am at line 2: "ayy will copy the current line to register to a
I go to line 30:  "bdd will cut the current line to register b.
I am at the end of file : "ap  and "bp  will paste line 2 and line 30 at end of file.

"ap pastes a copy of the 'a' register's contents into the text after the cursor and "aP pastes a copy from 'a' to before the current line.

capital letters can be used to append the content to a register. 
 "Ayy will append the current line to the register A.

To access all currently defined registers hit :reg

We can do some interesting things with registers.
for example if you want to execute a command which is at current line in vi what you do ?? There is a simple solution for it.
Copy the line you want to execute to a register -  "ayy 
Execute the content of register using '@'  -  :@a 

Read More