Profiling tool - How to use OProfile ?

OProfile can collect event information for the whole system in the background with very little overhead. OProfile mainly consists of the opcontrol shell script and the oprofiled daemon. The opcontrol script is used for configuring, starting, and stopping a profiling session, which are then recorded into sample files by oprofiled. And opreport is used to analyze...

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Unix command line tricks

1. Ever tried creating pdf files in your unix machine ?? man -t ascii | ps2pds - > ascii_man_page.pdf -t flag formats the output and ps2pds converts post script to pdf. hyphen (-) after ps2pdf command indicates it to read input from stdin and write output to stdout. 2. Want to terminate the script after first failure ? 'set -e' thats it. it does everything. $> cat setexit.sh #/bin/bash set...

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Programmable Completion : Autocomplete the arguments of your program

Auto completion is one of the best features in bash. How good if it completes argument for your program as well !! The Bash complete and compgen builtins make it possible for tab completion to recognize partial parameters and options to commands. In a very simple case, we can use complete from the command-line to specify a short list of acceptable parameters. with...

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compgen - List All Unix Commands !!

compgen is bash built-in command and it will show all available commands, aliases, and functions. and it is used to get the specific set of words from a word list ( ?? ) To list all the commands available : $ compgen -c alert c d egrep fgrep .. .. .. bzexe espdiff sol gnome-mines gnome-sudoku To list all the bash shell aliases available : $ compgen -a alert c d egrep fgrep grep l la To...

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Difference between array[@] and array[*] in shell

It is important for quoting and spacing that the ${array[@]}format (rather than ${array[*]}) is used, and also that double quotes are put around the whole construct.  items=(pen "permanent marker" pencil "temporary marker")   for item in ${items[@]} do echo "Item is : $item" done Item is : penItem is : permanentItem is : markerItem is : pencilItem is : temporaryItem is : marker for...

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A Bit Close Look At Vi - More On 'registers'

Note - read Marks & Registers before reading this post. There are some other ways of copy or delete text in vi. Working with paragraphs: If you are in paragraph text you can use  }  and  {  to move  cursor to the beginning or ending of the paragraph respectively.  so if you want to move a paragraph you can use  {  and  d} .  and...

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Vi - Marks and Registers

Marks: vi has 26 "marks". A mark is set to any cursor location using the m command.  Each mark is designated by a letter.  Thusma sets the 'a' mark to the current location, andms sets the 's' mark.   You can move to the line containing a mark using the ' (single quote) command.   Thus 'a moves to the beginning of the line...

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Shell Special variables and TEST flags

Here are some shell special variables: Special Shell Variables: VariableMeaning $0Filename of script $1Positional parameter #1 $2 - $9Positional parameters #2 - #9 ${10}Positional parameter #10 $#Number of positional parameters "$*"All the positional parameters (as a single word) * "$@"All the positional parameters (as separate strings) ${#*}Number of positional parameters ${#@}Number of...

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Parameters/String Operations on shell (Bash) without using any third party tools

Parameter Substitution and Expansion: ExpressionMeaning ${var}Value of var (same as $var) ${var-DEFAULT}If var not set, evaluate expression as $DEFAULT * ${var:-DEFAULT}If var not set or is empty, evaluate expression as $DEFAULT * ${var=DEFAULT}If var not set, evaluate expression as $DEFAULT * (value is assigned to var) ${var:=DEFAULT}If var not...

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Reading environment variables in python

The os module contains an interface to operating system-specific functions. this module can be used to access environment variables.  We can go with os.environ to get the value of environment variable. import os print os.environ['HOME'] but there is a catch, this method will raise KeyError variable does not exist  >>> print os.environ['HOME_NOT_EXIST'] Traceback...

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