Difference between revisions of "Miscellaneous commands"

Revision as of 06:43, 24 September 2007

This article will present various miscellaneous commands tested in Linux (running SuSE 10.2 and Mandriva). Most of these will be simple command line tools. Eventually, many of these will have their own article. For now, they are presented as is with absolutely no guarantee and zero responsibility on my part if they cause loss of information or files. Use at your own risk.

Google tricks

• Finding files:

-inurl:(htm|html|php) intitle:"index of" +"last modified" 
+"parent directory" +description +size +(jpg|png) "Lion"

• Finding documents:

-inurl:(htm|html|php) intitle:"index of" +"last modified"
+"parent directory" +description +size +(pdf|doc) "shakespeare"

• Phonebook:

rphonebook: John Doe Portland OR
bphonebook: Blue Sushi Seattle WA

Note: See Google Search Manual and Google command line help for more tricks.

Bulk image resize

If you are like me and have a high resolution digital camera, it is often necessary to resize the images before emailing them to friends and family. It is, of course, possible to manually resize them using Adobe Photoshop, The Gimp, or any other image editing programme. However, it is possible to automate this task using simple command line tools.

For an example, say you want to resize all of the jpeg images in your current directory to 800x600 and place them in a sub-directory called, "resized". Then you would execute the following commands:

find . -maxdepth 1 -name '*.jpg' -type f -exec convert -resize 800x600 {} resized/{} \;

It is also possible to have the above commands run recursively through a directory and its sub-directories like so:

find . -follow -name '*.jpg' -type f -exec convert -resize 800x600 {} ../resized/{} \;

Note that the programme convert is part of the ImageMagick suite and you will need to have it installed to use the above commands (it is, by default, in SuSE Linux and most distributions).

ps2png

• Convert PostScript (*.ps) files to PNG:

gs -sDEVICE=ppmraw -sOutputFile=- -sNOPAUSE -q foo.ps -c showpage -c quit |\
pnmcrop| pnmmargin -white 10 | pnmtopng >foo.png

Tracking down large files

Sometimes it is necessary to find files over a certain size and it can be somewhat tedious ls-ing through your many directories. The following command will list only those files over a certain size and only within the specified directory (and sub-directories):

find some_directory/ -size +2000k -ls

which will only list files over 2000 kb (2 MB).

Finding files containing a string in a directory hierarchy

In this example, all .php files will be searched for the string "MySQL" (case-insensitive with -i) and the line numbers will also be returned (using -n):

find . -name '*.php' -type f | xargs grep -n -i 'MySQL'

nrg2iso

There is a command line utility, nrg2iso, for converting to ISO files in Linux. Linux users can easily convert the NRG file using the dd command in the following way:

dd bs=1k if=myfile.nrg of=image.iso skip=300

Or, you can just mount it like so:

mount -o loop, offset=307200 /path/to/image.nrg /path/to/mount

Selecting random lines from a file

This example could be used for printing random quotes from a file (note: the following should be issued as a single command):

FILE="/some/file_name"; 
nlines=$(wc -l < "$FILE"); 
IFS=$'\n'; 
array=($(<"$FILE")); 
echo "${array[$((RANDOM%nlines))]}"

Here, nlines holds the total number of lines in the file. The file is read into an array (note the use of IFS — this splits the lines based on '\n'). Then, once the array has been populated, print a random line from it.

Printing a block of text from a file

Say you have a file, foo, and it contains the following lines (note the capital letters and the full stop in line six):

one blah blah
Two blah blah
three blah blah 3, 4
Four blah blah
five blah blah 5, 6
six blah blah.

• If you only want to print out lines 3, 4, and 5, execute the following command:

awk "/three/,/five/" < foo

• If you only want to print out lines starting with a capital "F", execute the following command:

awk "/^F/" < foo

• If you only want to print out lines ending in a full stop, execute the following command:

awk "/\.$/" < foo

• Finally, if you only want to print out lines containing the numbers "5" and "6", execute the following command:

awk "/[5-6]/" < foo

Note: See awk for details.

Linux I/O redirection

• The following command saves stdout and stderr to the files "out.txt" and "err.txt", respectively:

./cmd 1>out.txt 2>err.txt

• The following command appends stdout and stderr to the files "out.txt" and "err.txt", respectively:

./cmd 1>>out.txt 2>>err.txt

• The following command functions similar to the above two commands, but also copies stdout and stderr to the files "stdout.txt" and "stderr.txt", respectively:

(((./cmd | tee stdout.txt) 3>&1 1>&2 2>&3\
| tee stderr.txt) 3>&1 1>&2 2>&3) 1>out.txt 2>err.txt

Note: The above should be entered as one command (ie, the line that ends with a backslash is only continued on the next line because of the formatting constraints of this page).

Also note that Linux uses the following redirection codes/handles (see: redirection):

• 0 = stdin
• 1 = stdout
• 2 = stderr

Count number of n-word lengths

for i in `seq 1 32` {
     egrep '^.{'$i'}$' /usr/share/dict/words | wc -l
}
# OR (depending on your shell),
for i in `seq 1 32`; do egrep '^.{'$i'}$' /usr/share/dict/words | wc -l; done

Then paste the numbers together (or, just add them to the above for-loop):

seq 1 32 | paste - tmp_n-word_lenghts.dat >n-word_lengths.dat

Edit a file from the CLI using Perl

perl -p -i.bak -e 's|before|after|' filename  # backup of original file 'filename.bak'

perl -p -i -e 's|before|after|ig' filename

-p 

Execute the command for every line of the file.

-i 

Invokes in place editing. If a backup extension is provided, a backup of the original file will be made with the extension provided. e.g. -i.bak.

-e 

Invoke command.

Command-line calculator

% echo "111111111 * 111111111" | bc
  12345678987654321
% echo -e "sqrt(25)\nquit\n" | bc -q -i
  5

Also,

% let x=3*4-6; echo $x

Split large files into small pieces

% ls -lh mylargefile
  -rw-r--r--  1 foo users 800M Feb 18 11:17 mylargefile
% split -b 2m largefile mylargefile_
% ls -lh mylargefile_* | head 3
  -rw-r--r--  1 foo users 2.0M Feb 18 11:19 mylargefile_aa
  -rw-r--r--  1 foo users 2.0M Feb 18 11:19 mylargefile_ab
  -rw-r--r--  1 foo users 2.0M Feb 18 11:19 mylargefile_ac
  ...

Stego trick using built-in Linux utilities

cat foo.zip >> bar.gif  # "hides" 'foo.zip' inside 'bar.gif'
xv bar.gif     # views just fine
unzip bar.gif  # extracts 'foo.zip'

cat and squeeze-blank

The cat utility has a nice little feature that allows you to "squeeze" multiple blank lines into a single line. In other words, never print more than one single blank line.

cat -s foo | tr -d '\f'

The second command, tr, just says delete ("-d") any form feeds (you would use this if you want to print the file).

Create a favicon

• Step 1: Download png2ico and install (just type make)
• Step 2: Create a PNG using something like GIMP (make sure the image is square and small; e.g. 128x128, 300x300, etc).
• Step 3: Convert the image to a 32x32 PNG (or 16x16, if you wish)

convert foo.png -resize 32x32 favicon.png

• Step 3: Convert to icon

png2ico favicon.ico favicon.png
# ~ OR ~
png2ico favicon.ico logo16x16.png logo32x32.png

see: Creative Favicons: When Small Is Beautiful for ideas

Misc

• Save man pages as plain text:

man grep | col -b > grep.txt

• Display the total number of files in the current working directory and all of its subdirectories:

find . -type f -print | wc  -l

• Display a list of directories and how much space they consume, sorted from the largest to the smallest:

du | sort -nr

• Format text for printing:

cat poorly_formatted_report.txt | fmt | pr | lpr
cat unsorted_list_with_dupes.txt | sort | uniq | pr | lpr

• Delete files older than n days:

find /path/to/files* -mtime +5 -exec rm {} \;

• Download multiple files in bash using for-loop:

for (( a=1; a<=96; a++ )) ;do wget -c http://www.manga.com/images/qtvim/Vol_01/$a.jpg; done

• Multiple unzip: The following command will unzip all zip files in the current directory:

for i in $(ls *.zip); do unzip $i; done

• Copying files through tar filter:

(cd /path/dir/from && tar -cvf - .) | (cd /path/dir/to && tar -xvf -)

• Look up the definition of a word from the CLI:

curl dict://dict.org/d:word

• Timed read-input using bash:

answer="yes";read -p "Do you wish to install now? " -t 10 answer;echo " Timed out; asumming $answer";

• Check current battery charge system temperature:

acpi -t

• Display information about all system users:

finger -l

• Display distribution and version:

cat /etc/issue

See also

• awk/gawk
• find
• xargs
• ImageMagick
• convert
• Bash
• tee

To Do

Lifehacker

• Geek to Live: Back up Gmail with fetchmail
• Geek to Live: Keep your calendar in plain text with Remind
• Getting things done with rule-based list processing
• Hack Attack: Firefox and the art of keyword bookmarking

Howtoforge

• The New Hacker's Dictionary
• Build Your Own Video Community With Lighttpd And FlowPlayer (Debian Etch)
• How to perform a point in time restoration using ZRM for MySQL
• Step-by-Step IPP based Print Server using CUPS
• Securing Your Server With A Host-based Intrusion Detection System
• How To Monitor A System With Sysstat On Centos 4.3
• Accessing Windows Or Samba Shares Using AutoFS

Sourceforge

• The Arusha Project (ARK)
• Command Line Progress Bar (bar)
• SMBNetFS — a Linux/FreeBSD filesystem that allow you to use samba/microsoft network in the same manner as the network neighborhood in Microsoft Windows.

Wikipedia

• wikipedia:Category:GNU project software
• wikipedia:GNU Scientific Library
• wikipedia:DotGNU
• wikipedia:Patch_(Unix) (patch)
• wikipedia:Filesystem in Userspace (aka "FUSE")

Other

• phpGroupWare
• HOWTO Auto mount filesystems (AUTOFS)
• sshfs - secure and transparent access to remote filesystems
• Become a digital video editing guru using Linux tools
• nixCraft
• Linux.ie
• 8-Bit ASCII Codes and HTML Equivalents
• RRDtool — data logging and graphing application.
• 15 Javascript Snippets You Can't Live Without
• Kexi Project — "Microsoft Access for Linux"
• The Lazy Guide to Installing Knoppix on a USB Key
• Tracker
• How to Write a Spelling Corrector
• Speaking UNIX, Part 8: UNIX processes
• O'Reilly School
• Linux: system administration — by Lena
• Free Linux books (on-line only)
• 25 Code Snippets for Web Designers (Part5)
• reCAPTCHA
• JSAN.org &mdsash; JavaScript Archive Network is a comprehensive resource for Open Source JavaScript libraries and software.
• TrueCrypt Tutorial: Truly Portable Data Encryption
• lsof
• jQuery — a fast, concise, JavaScript Library that simplifies how you traverse HTML documents, handle events, perform animations, and add Ajax interactions to your web pages.
• An Introduction to Linux Audio
• Install any Linux distro directly from hard disk without burning any DVD
• Designing Digg Picture Website in a Matter of Hours
• incron — execute commands based on filesystem activity

External links

• How To Look Like A UNIX Guru
• Scripting Partition Creation In Linux Using Fdisk
• Scripts For Imaging/Cloning Disks Using Partimage Under Linux
• Configuring Vacation Mail With Procmail