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Top Forums Programming Reading a particular line from a .txt file Post 302425806 by jim mcnamara on Sunday 30th of May 2010 11:08:48 AM
Old 05-30-2010
When the lines are a fixed record length, you can call seek() or fseek() in C++, C to get to a known line position.
this is c:
Code:
void seek_to_line(FILE *in, const long recl, const long lineno)
{
     fseek(in, lineno * recl, SEEK_SET);
}

This places the file pointer at the beginning of lineno, assuming recl is fixed.

Otherwise you can try to optimize I/O (see Steven's Advanced Programming in the UBIX Environment) by increasing
buffersize
Code:
FILE *in=fopen("somefile, "r");
int lineno=250002;
char tmp[256]={0x0};
char buf[16384]={0x0};

setvbuf(in, buf, 16384, _IOFBF );
while(--lineno)
   fgets(tmp, sizeof(tmp), in);

you have to call setvbuf BEFORE any I/O on the stream

Last edited by jim mcnamara; 05-30-2010 at 12:16 PM..
 

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Really Slick ScreenSavers(1)				      General Commands Manual				      Really Slick ScreenSavers(1)

NAME
cyclone - tornado screen saver. SYNOPSIS
cyclone [--root/-r] [--maxfps/-x number] [--vsync/-y number] [--dpms/-M number] [--cyclones/-c number] [--particles/-p number] [--size/-i number] [--complexity/-C number] [--speed/-e number] [--stretch/-s] [--no-stretch/-S] [--showcurves/-v] [--no-showcurves/-V] DESCRIPTION
From Terry Walsh (http://reallyslick.com): "This screen saver makes tornadoes on your screen. I wrote it for my storm chasing partner, but you can have it too." Ported to Linux by Tugrul Galatali. OPTIONS
--root Draw on the root window. --maxfps number Set maximum frame rate. --vsync number Limit redraws to specified number of vertical refreshes. 0 - 100. Default: 1 --dpms number Stop rendering new frames if the display is not on. 0 - 1. Default: 1 --cyclones number Number of cyclones. 1 - 10. Default: 1 --particles number Particles per cyclone. 1 - 10000. Default: 200 --size number Particle size. 1 - 100. Default: 7 --complexity number Cyclone complexity. 1 - 10. Default: 3 --speed number Speed. 1 - 100. Default: 10 --stretch Stretch. Default: True --showcurves Show Curves. Default: False ENVIRONMENT
DISPLAY to get the default host and display number. SEE ALSO
X(1), COPYRIGHT
Copyright (C) 2002 by Terry Walsh and Tugrul Galatali. Cyclone is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License version 2 as published by the Free Software Foundation. Cyclone is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. AUTHOR
Terry Walsh and Tugrul Galatali <tugrul@galatali.com> X Version 11 Really Slick ScreenSavers(1)
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