No syntax highlighting in vimdiff

Vim Syntax highlight often mixed with diff color, which makes text unreadable.

Add following line in ~/.vimrc to turn off syntax off in vimdiff

if &diff | syntax off | endif

IO Redirection - Swapping stdout and stderr (Advanced)

% (sh myscript.sh 3>&2 2>&1 1>&3) 2>/dev/null
I'm stderr
% (sh myscript.sh 3>&2 2>&1 1>&3) >/dev/null 
I'm stdout

python 3 line to solve 8 queen

from itertools import *
c = range(8)
print len([v for v in permutations(c) if 8==len(set(v[i]+i for i in c))==len(set(v[i]-i for i in c))])

Python overwrite printed line, e.g. text progress

\r will reset the cursor to the beginning of the line.

>>> for i in range(100):
...    time.sleep(1)
...    sys.stdout.write("\r%d%%" %i)    # or print >> sys.stdout, "\r%d%%" %i,
...    sys.stdout.flush()
... 

Benchmark CPU in SHELL

$ time echo "scale=5000; a(1)*4" | bc -l

brackets, parentheses, curly braces in BASH

In Bash, test and [ are builtins.

The double bracket enables additional functionality. For example, you can use && and || instead of-a and -o and there's a regular expression matching operator =~.

The braces, in addition to delimiting a variable name are used for parameter expansion so you can do things like:

• Truncate the contents of a variable
  $ var="abcde"; echo ${var%d*}
abc
• Make substitutions similar to sed
  $ var="abcde"; echo ${var/de/12}
abc12
• Use a default value
  $ default="hello"; unset var; echo ${var:-$default}
hello
• and several more

Vim folding, auto fold xml, fold, unfold

To allow folds based on syntax add something like the following to your .vimrc:

set foldmethod=syntax
set foldlevelstart=1

let javaScript_fold=1         " JavaScript
let perl_fold=1               " Perl
let php_folding=1             " PHP
let r_syntax_folding=1        " R
let ruby_fold=1               " Ruby
let sh_fold_enabled=1         " sh
let vimsyn_folding='af'       " Vim script
let xml_syntax_folding=1      " XML




zo -- To open a fold block

zc -- To fold a block

zr -- Fold less

zm -- Fold more