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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
Quote:
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.
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.
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.txtoutput from above - x=-5.55 z=6.5
Quote:
why re-invent wheels?
Regards,
Gaurav
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LEARN ABOUT REDHAT
unix2dos
unix2dos(1) General Commands Manual unix2dos(1) NAME
unix2dos - UNIX to DOS text file format converter SYNOPSYS
unix2dos [options] [-c convmode] [-o file ...] [-n infile outfile ...] Options: [-hkqV] [--help] [--keepdate] [--quiet] [--version] DESCRIPTION
This manual page documents unix2dos, the program that converts text files in UNIX format to DOS format. OPTIONS
The following options are available: -h --help Print online help. -k --keepdate Keep the date stamp of output file same as input file. -q --quiet Quiet mode. Suppress all warning and messages. -V --version Prints version information. -c --convmode convmode Sets conversion mode. Simulates unix2dos under SunOS. -o --oldfile file ... Old file mode. Convert the file and write output to it. The program default to run in this mode. Wildcard names may be used. -n --newfile infile outfile ... New file mode. Convert the infile and write output to outfile. File names must be given in pairs and wildcard names should NOT be used or you WILL lost your files. EXAMPLES
Get input from stdin and write output to stdout. unix2dos Convert and replace a.txt. Convert and replace b.txt. unix2dos a.txt b.txt unix2dos -o a.txt b.txt Convert and replace a.txt in ASCII conversion mode. Convert and replace b.txt in ISO conversion mode. unix2dos a.txt -c iso b.txt unix2dos -c ascii a.txt -c iso b.txt Convert and replace a.txt while keeping original date stamp. unix2dos -k a.txt unix2dos -k -o a.txt Convert a.txt and write to e.txt. unix2dos -n a.txt e.txt Convert a.txt and write to e.txt, keep date stamp of e.txt same as a.txt. unix2dos -k -n a.txt e.txt Convert and replace a.txt. Convert b.txt and write to e.txt. unix2dos a.txt -n b.txt e.txt unix2dos -o a.txt -n b.txt e.txt Convert c.txt and write to e.txt. Convert and replace a.txt. Convert and replace b.txt. Convert d.txt and write to f.txt. unix2dos -n c.txt e.txt -o a.txt b.txt -n d.txt f.txt DIAGNOSTICS
BUGS
The program does not work properly under MSDOS in stdio processing mode. If you know why is that so, please tell me. AUTHOR
Benjamin Lin - ( blin@socs.uts.edu.au ) MISCELLANY
Tested environment: Linux 1.2.0 with GNU C 2.5.8 SunOS 4.1.3 with GNU C 2.6.3 MS-DOS 6.20 with Borland C++ 4.02 Suggestions and bug reports are welcome. SEE ALSO
dos2unix(1) 1995.03.31 unix2dos v2.2 unix2dos(1)