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> I've seen several articles in the past with titles like "Top 10 things you didn't know about bash programming." These articles are disappointing on two levels: first of all, the tricks are almost always things I already knew. And secondly, if you want to write portable programs, you can't depend on bash features (not every platform has bash!). POSIX-like shells, however, are much more widespread. > Since writing redo, I've had a chance to start writing a few more shell scripts that aim for maximum portability, and from there, I've learned some really cool tricks that I haven't seen documented elsewhere. Here are a few.

#unix #posix #sh #bash

Extract & mirror cache url's from google search pages

Saved search pages go in, cache links come out. It's handy for mirroring a dead site by using site:domain.com as the search parameter.

Notes: Without rate limiting I was blocked after request #169. However, there were no issues when using the limits below. The wait time can probably go much lower though. The empty user-agent is required for wget to work.

pcregrep -hoM http://webcache\.googleusercontent\.com/search\\?q\\=cache:$.+?$$?=[+]\(.+$\"$.*$\>Cached\) searc*.html > cachelist.txt wget --wait 15s --random-wait --user-agent="" -i cachelist.txt To match the junk part of the filename (search?q=cache:4Ip_t8yQ-rL2:) use this: search\?q=cache:............:

edit: updated for new search output & lowered wait to 15s

#grep #regex #wget #google #backup

Set mp3 date tag as YYYY-MM-DD based on mtime

Particularly useful for large, poorly tagged radio archives mirrored with wget. Processes files in the working directory matching the patters specified.

Requires: mutagen (for tagging)

for FILE in *.mp3; do mid3v2 --date=$(perl -e '@d=localtime ((stat(shift))[9]); printf "%4d-%02d-%02d", $d[5]+1900,$d[4]+1,$d[3]' $FILE) $FILE; done

#perl #bash #tagging

"A simple and dirty HTML/XML template library for Python 3."

>>> from dirty.html import * >>> page = xhtml( ... head( ... title("Dirty"), ... meta(name="Author", content="Hong, MinHee <[email protected]>") ... ), ... body( ... h1("Dirty"), ... p("Dirty is a simple DSEL template library that...") ... ) ... ) >>> print(page) <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" /> <head> <title>Dirty</title> <meta content="Hong, MinHee <[email protected]>" name="Author" /> </head> <body> <h1>Dirty</h1> <p>Dirty is a simple DSEL template library that...</p> </body> </html>

#python #html

Time formatting in Haskell

showTime :: Int -> Int -> String showTime hours minutes | hours == 0 = "12" ++ ":" ++ showMin ++ " am" | hours <= 11 = (show hours) ++ ":" ++ showMin ++ " am" | hours == 12 = (show hours) ++ ":" ++ showMin ++ " pm" | otherwise = (show (hours - 12)) ++ ":" ++ showMin ++ " pm" where showMin | minutes < 10 = "0" ++ show minutes | otherwise = show minutes

Main> showTime 13 37 "1:37 pm"

From [Haskell for C Programmers](http://www.haskell.org/~pairwise/intro/intro.html).

#haskell

alloy-d-blog-deactivated2019090

Command name is 25% fewer characters to type! Save days of free-time! Heck, it’s 50% shorter compared to grep -r.

Why use ack? (via lloyda2)

#perl #grep

>>> a = 500 >>> b = 500 >>> a is b False >>> c = 200 >>> d = 200 >>> c is d True

"Can you surmise why this inconsistency happens?"

#python

Disable the new look in Safari 4

The new tabs in Safari 4 are nice, but I prefer the old classic look. If you're like me, like I know I am, use these commands in the terminal to disable the new look:

defaults write com.apple.Safari DebugSafari4TabBarIsOnTop -bool NO defaults write com.apple.Safari DebugSafari4IncludeToolbarRedesign -bool NO defaults write com.apple.Safari DebugSafari4LoadProgressStyle -bool NO

#os x

"A generator and a list used like a cache."

class GeneratorList(object): def __init__(self, generator): self.__generator = generator self.__list = [] def __getitem__(self, index): for _ in range(index - len(self.__list) + 1): self.__list.append(self.__generator.next()) return self.__list[index]

#python

def trim(docstring): if not docstring: return '' lines = docstring.expandtabs().splitlines() # Determine minimum indentation (first line doesn't count): indent = sys.maxint for line in lines[1:]: stripped = line.lstrip() if stripped: indent = min(indent, len(line) - len(stripped)) # Remove indentation (first line is special): trimmed = [lines[0].strip()] if indent < sys.maxint: for line in lines[1:]: trimmed.append(line[indent:].rstrip()) # Strip off trailing and leading blank lines: while trimmed and not trimmed[-1]: trimmed.pop() while trimmed and not trimmed[0]: trimmed.pop(0) return '\n'.join(trimmed)

With this algorithm, an indented documentation string such as this…

def foo(): """ A multi-line docstring. """

…is converted to: "A multi-line\ndocstring."

#python

$ sudo su - # du -sh /opt 6.4G /opt # port clean -f --all installed ---> Cleaning apr ---> Cleaning apr-util ... # du -sh /opt 6.3G /opt # port -f uninstall inactive ---> Uninstalling autoconf @2.62_0 ---> Uninstalling automake @1.10.1_0 ... # du -sh /opt 5.4G /opt

#macports #os x

find . -type d -empty -exec rmdir {} \;

#bash

nononononololnostopitlol

TinyP2P: A 15 line long Python P2P Application

codedump

Via nosmo:

# tinyp2p.py 1.0 (documentation at http://freedom-to-tinker.com/tinyp2p.html) import sys, os, SimpleXMLRPCServer, xmlrpclib, re, hmac # (C) 2004, E.W. Felten ar,pw,res = (sys.argv,lambda u:hmac.new(sys.argv[1],u).hexdigest(),re.search) pxy,xs = (xmlrpclib.ServerProxy,SimpleXMLRPCServer.SimpleXMLRPCServer) def ls(p=""):return filter(lambda n:(p=="")or res(p,n),os.listdir(os.getcwd())) if ar[2]!="client": # license: http://creativecommons.org/licenses/by-nc-sa/2.0 myU,prs,srv = ("http://"+ar[3]+":"+ar[4], ar[5:],lambda x:x.serve_forever()) def pr(x=[]): return ([(y in prs) or prs.append(y) for y in x] or 1) and prs def c(n): return ((lambda f: (f.read(), f.close()))(file(n)))[0] f=lambda p,n,a:(p==pw(myU))and(((n==0)and pr(a))or((n==1)and [ls(a)])or c(a)) def aug(u): return ((u==myU) and pr()) or pr(pxy(u).f(pw(u),0,pr([myU]))) pr() and [aug(s) for s in aug(pr()[0])] (lambda sv:sv.register_function(f,"f") or srv(sv))(xs((ar[3],int(ar[4])))) for url in pxy(ar[3]).f(pw(ar[3]),0,[]): for fn in filter(lambda n:not n in ls(), (pxy(url).f(pw(url),1,ar[4]))[0]): (lambda fi:fi.write(pxy(url).f(pw(url),2,fn)) or fi.close())(file(fn,"wc"))

#python

>>> stuff = { ... 'hello': 'world', ... 'numbers': range(3), ... } >>> import pickle >>> data = pickle.dumps(stuff) >>> len(data) 63 >>> print data (dp0 S'hello' p1 S'world' p2 sS'numbers' p3 (lp4 I0 aI1 aI2 as. >>> pickle.loads(data) {'hello': 'world', 'numbers': [0, 1, 2]}

#python

Extended slices in Python

To access even-indexed elements of a list, use the extended slice feature of Python.

>>> range(20)[::2] [0, 2, 4, 6, 8, 10, 12, 14, 16, 18]

This can be used to access every third element by using ::3 and so on.

To reverse a list, use the extended slice with an argument of -1.

>>> range(8)[::-1] [7, 6, 5, 4, 3, 2, 1, 0]

#python

Disable the 3D-dock in Leopard

If you hate the fancy 3D-dock in Leopard, or just think that it doesn't match your current wallpaper (this happens for me a lot), open a Terminal and type these:

defaults write com.apple.dock no-glass -boolean YES killall Dock

#os x

Quake3's Fast Inverse Square Root Function

Oh my:

float InvSqrt (float x){ float xhalf = 0.5f*x; int i = *(int*)&x; i = 0x5f3759df - (i>>1); x = *(float*)&i; x = x*(1.5f - xhalf*x*x); return x; }

According to one of the guys [supposedly responsible](http://www.beyond3d.com/content/articles/8/) for this (arguably) legendary piece of code, "it's just Newton-Raphson iteration with a very clever first approx." And if you're interested, you can also read about [why it works](http://betterexplained.com/articles/understanding-quakes-fast-inverse-square-root/).

#c

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