Join odd and even numbered lines

sed:

sed '$!N;s/\n/,/'


awk:

awk 'NR%2==0 {print p","$0;} NR%2 {p=$0;}'


paste:

paste - -


--------------------------
Seems  I like paste most. To join 3 consecutive lines:

paste - - -

Python Profiler

def do_cprofile(func):
    def profiled_func(*args, **kwargs):
        import cProfile
        profile = cProfile.Profile()
        try:
            profile.enable()
            result = func(*args, **kwargs)
            profile.disable()
            return result
        finally:
            profile.print_stats(sort=1)
    return profiled_func

try:
    from line_profiler import LineProfiler

    def do_profile(follow=[]):
        def inner(func):
            def profiled_func(*args, **kwargs):
                try:
                    profiler = LineProfiler()
                    profiler.add_function(func)
                    for f in follow:
                        profiler.add_function(f)
                    profiler.enable_by_count()
                    return func(*args, **kwargs)
                finally:
                    profiler.print_stats()
            return profiled_func
        return inner

except ImportError:
    def do_profile(follow=[]):
        "Helpful if you accidentally leave in production!"
        def inner(func):
            def nothing(*args, **kwargs):
                return func(*args, **kwargs)
            return nothing
        return inner


@do_profile(follow=[fun2])
def fun1():
    fun2()
    pass


@do_cprofile()
def fun2()
    pass

Java cpu profiling with hprof

Set JAVA_OPTS:

-Xrunhprof:cpu=samples,interval=10,depth=8

There will be a  file called "java.hprof.txt" in your working directory 

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()
...