Reading a particular line from a .txt file Post: 302425830

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Top Forums Programming Reading a particular line from a .txt file Post 302425830 by gaurav1086 on Sunday 30th of May 2010 03:24:03 PM

05-30-2010

Registered User

Quote:

Originally Posted by mugga

Hi,
I have a .txt file which contains the x, y and z co-ordinates of particles which I am trying to cast for a particular compound. The no. of particles present is of the order of 2 billion and hence the size of the text file is of the order of a few Gigabytes. The particles have been casted layer wise - thus, if there are 15000 layers in which I have casted the particles, there are approx. 2 billion/15000 particles in each layer. Thus, every 2 billion/15000 particles have the same Y co-ordinate. Now, I need to read the particles at a given value of Y (say y = 10). I wrote a small program, where I had used fin.seekg( ). However I realized that the seeking of the position from where the file has to be read is not done line-wise, but is done character-wise. Could someone please tell me how I could start seeking from a particular line in the file using a simple C++ program.

Considering the layout of your file to be in this form

X Y Z
-5.55 4.44 6.5
10.66 44.5 85.99
.....
......
.....
The values are separated by whitespace(s).

A simple awk liner will rid of of your messy C++ code.

Code:

 awk -v y=  '$2==y{print "x="$1,"z="$3}' file.txt

subsitute the value of y . e.g. awk -v y=4.44 '.........'
output from above - x=-5.55 z=6.5

Quote:

why re-invent wheels?

Hope this helps,
Regards,
Gaurav

gaurav1086

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LEARN ABOUT DEBIAN

anemotaxis

anemotaxis(6x)							XScreenSaver manual						    anemotaxis(6x)

NAME

       anemotaxis - directional search on a plane.

SYNOPSIS

       anemotaxis  [-display  host:display.screen]  [-visual  visual]  [-window]  [-root]  [-delay  number]  [-distance  number] [-sources number]
       [-searchers number] [-fps]

DESCRIPTION

       The program demonstrates a search algorithm designed for locating a source of odor in turbulent atmosphere. The odor is convected  by  wind
       which  has  a  constant mean direction and fluctuations around it. The searcher is able to sense the odor and determine local instantaneous
       wind direction. The goal is to find the source in the shortest mean time.  Some animals face this task to find mates, food, home etc.  They
       exhibit very particular, zigzagging search trajectories.

       This  is  modeled as a search on a discrete two-dimensional lattice. The source releases particles that drift with constant velocity in one
       direction and walk randomly in the other direction. The searcher knows if it hit a particle, and if so, particle's position one	time  step
       earlier (local wind direction). The program paints sources and particles released by them as well as trajectories of searchers who are try-
       ing to capture the sources.

OPTIONS

       -visual visual
	       Specify which visual to use.  Legal values are the name of a visual class, or the id number (decimal or hex) of a specific visual.

       -window Draw on a newly-created window.	This is the default.

       -root   Draw on the root window.

       -delay number
	       Per-frame delay, in microseconds.  Default: 20000 (0.02 seconds.).

       -distance number
	       Max initial distance to the source .  10 - 250.	Default: 40.

       -sources number
	       Max number of sources.  Default: 25.

       -searchers number
	       Max number of searchers. Default: 25.

       -fps    Display the current frame rate and CPU load.

ENVIRONMENT

       DISPLAY to get the default host and display number.

       XENVIRONMENT
	       to get the name of a resource file that overrides the global resources stored in the RESOURCE_MANAGER property.

SEE ALSO

       X(1), xscreensaver(1)

COPYRIGHT

       Copyright (C) 2004 by Eugene Balkovsky.	Permission to use, copy, modify, distribute, and sell this software and its documentation for  any
       purpose	is  hereby  granted without fee, provided that the above copyright notice appear in all copies and that both that copyright notice
       and this permission notice appear in supporting documentation.  No representations are made about the suitability of this software for  any
       purpose.  It is provided "as is" without express or implied warranty.

AUTHOR

       Eugene Balkovsky

X Version 11							5.15 (28-Sep-2011)						    anemotaxis(6x)