HOME

  0. Internet
  1. Text
  2. Graphics
  3. System
  4. File
  5. Misc
  6. Palm
  7. OS X

BLOG

DOCS

FAQ

RSS (?)

Linux: wiping free disk space #
Besides removing cruft, BleachBit can wipe free disk space (similar to SDelete or cipher /W:C under Windows). In addition to source code, a number of Linux and Windows binaries are available for download. (via Super User)

/nix | Feb 26, 2012

Verify disk wipe #
After zero-filling a disk, verify with hexdump or md5sum and All-Zero Hash Calculator. On a 2.5" 500GB SATA drive, both hexdump and md5sum took 144m16s to run.

hexdump:

   $ hexdump /dev/sda
   0000000 0000 0000 0000 0000 0000 0000 0000 0000
   *
   7470c06000

7470c06000 hex = 500107862016 decimal, which is the number of bytes on disk.

md5sum and All-Zero Hash Calculator:

   $ md5sum /dev/sda
   91564846bfd6055945b31bbd831378a7

You'll need the number of bytes or sectors (the latter may be listed on the drive sticker as LBA) to verify the hash:

   $ fdisk -l /dev/sda
   Disk /dev/sda: 500.1 GB,  500107862016 bytes

   $ testdisk /dev/sda
   Proceed > None > Advanced > Size in sectors
                                976773168

/nix | Jan 29, 2012

Using wget on Amazon to download search results #
Neither Google nor Amazon index used book descriptions from sellers, making it difficult to find unique or mislisted volumes. In order to download these comments for searching with ack, wget was tried:

$ wget "http://www.amazon.com/gp/offer-listing/0131103628/?condition=used"
...
HTTP request sent, awaiting response... 204 NoContent
...

Hrm. How about omitting the User-Agent header?

$ wget --user-agent="" "http://www.amazon.com/gp/offer-listing/0131103628/?condition=used"
...
HTTP request sent, awaiting response... 200 OK
...

Bingo. If there is more than one page of listings (i.e., more than 15 used books available), all pages can be downloaded via something like wget -i urls.txt --user-agent="", where urls.txt contains one URL per line:

http://www.amazon.com/gp/offer-listing/0131103628/ref=olp_page_1?startIndex=0&condition=used
http://www.amazon.com/gp/offer-listing/0131103628/ref=olp_page_2?startIndex=15&condition=used
http://www.amazon.com/gp/offer-listing/0131103628/ref=olp_page_3?startIndex=30&condition=used

/nix | Dec 01, 2011

HTML2Markdown and much more #
Pandoc can convert from:

markdown
reStructuredText
textile
HTML
LaTeX

to:

plain text
markdown
reStructuredText
HTML
LaTeX
ConTeXt
PDF
RTF
DocBook XML
OpenDocument XML
ODT
GNU Texinfo
MediaWiki markup
textile
groff man pages
Emacs org-mode
EPUB ebooks
S5 and Slidy HTML slide shows

In addition to source code, *nix, OS X, and Windows binaries are available.

/nix | Nov 03, 2011

Find ALL CAPS 8.3 filenames which may contain digits #
Given a directory of files like this:

AD2IWFB6.txt
An_Important_File.txt
BB0IA29Q.txt
C2MMT30I.txt
CANTDELETETHISONE.txt
Y9S29CC0.txt
z.doc
ZZQ0LII7.txt

list the ALL CAPS files which are eight characters long, with or without numbers included, and ending in ".txt" like so:

$ ls -1 | ack ^[A-Z0-9]{8}\.txt$
AD2IWFB6.txt
BB0IA29Q.txt
C2MMT30I.txt
Y9S29CC0.txt
ZZQ0LII7.txt

(find -regex had a problem with the regular expression, so just went with ack instead. ack -g REGEX didn't match the regex either, perhaps because it matches based on both the relative path and filename?)

Delete the matching files by simply piping to xargs:

$ ls -1 | ack ^[A-Z0-9]{8}\.txt$ | xargs rm

/nix | Oct 07, 2011

Execute a command every x seconds indefinitely #
As cron's smallest increment is one minute, here are two methods for executing a command every five seconds:

   $ watch -n 5 echo "foo"
   $ while true; do echo "foo"; sleep 5; done

/nix | Sep 29, 2011

Learn programming concepts using Bash shell #
Mendel Cooper's Advanced Bash-Scripting Guide is "an in-depth exploration of the art of shell scripting... suitable for classroom use as a general introduction to programming concepts". Revision 6.4 was released just a few weeks ago in several formats.

/nix | Sep 18, 2011

Sequence expressions in wget and curl #
Given a range of JPGs to batch download:

http://example.com/manga/manga_06p01.jpg
http://example.com/manga/manga_06p02.jpg
...
http://example.com/manga/manga_06p99.jpg

one approach using wget would be:

$ wget http://example.com/manga/manga_06p{00..99}.jpg

Bash 4 is required for brace expansion using a range. Unfortunately, the expression fails to expand at all when read from a file (e.g., $ wget -i urls.txt).

curl, on the other hand, does not depend on Bash for sequencing:

$ curl -O http://example.com/manga/manga_06_p[00-99].jpg

so it will correctly parse sequences in a properly-formatted text file (e.g., urls.txt):

url = "http://example.com/manga/manga_06_p[00-99].jpg"
url = "http://example.com/manga/manga_07_p[00-99].jpg"
url = "http://example.com/manga/manga_08_p[00-99].jpg"

like so:

$ curl --remote-name-all -K urls.txt

/nix | Sep 12, 2011

Save all terminal text with script #
Script makes a typescript of everything printed in the terminal (saved to a file named typescript in the current directory by default):

$ script
Script started, output file is typescript
$ echo 'this is being recorded!'
this is being recorded!
$ exit
exit

Script done, output file is typescript
$ head typescript
Script started on Sun Jul 17 07:25:25 2011
bash-3.2$ echo 'this is being recorded!'
this is being recorded!
bash-3.2$ exit
exit

Script done on Sun Jul 17 07:25:51 2011

/nix | Jul 17, 2011

When you need a quick & simple calculator in Bash... #

$ bc -lq
1+1
2
quit

$ echo $((1+1))
2

$ echo $[1+1]
2

/nix | Jul 17, 2011

Categories

/blosxom
/eink
/mac
/misc
/nix
/palm
/windows

Blosxom Archive

2012: 5 4 3 2 1
2011: 12 11 10 9 8 7 6 5 4 3 2 1
2010: 12 11 10 9 8 7 6 5 4 3 2 1
2009: 12 11 10 9 8 7 6 5 4 3 2 1
2008: 12 11 10 9 8 7 6 5 4 3 2 1
2007: 12 11 10 9 8 7 6 5 4 3 2 1
2006: 12 11 10 9 8 7 6 5 4 3 2 1
2005: 12 11 10

Blogger Archive

2005: 10 9 8 7 6 5 4 3 2 1
2004: 12 11 10 9 8 7 6 5 4 3 2 1
2003: 12 11 10 9 8 7 6

Ezine Archive

2004: 4 3 2 1
2003: 12 9 8 7 6 5 4 2 1
2002: 12 10 9 8 7 6 5 3 2 1
2001: 12 11 10