c program help

munna_dude · 10-18-2007, 02:14 AM

hi all
i have to write some script in c program
i tried this

Code:

//cc simple.c -o simple
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(void)
{

char bb=system("cat file.txt | sed -n '/Underlying Value/,/]Top/p' | egrep -v 'Underlying Value|]Top' | sed 's/\[[0-9]\{1,\}\]//g' > /home/munna/Desktop/munna.txt");
printf("******** %s \n",bb);

  return 0;
}

and the file.txt is

Quote:

[1]Home > [2]F&O >
Watch

All contracts of NIFTY
As on Hours IST

Instrument Type Underlying Expiry Date Option Type High
Price Low Prev Close of contracts traded
Turnover Lakhs Underlying Value

[5]AAAAA [6]GGGGGG [7]25OC200 - - 5389.80 5203.10 5673.15 5255.00
89085 234115.83 5143.90
[8]AAAAA [9]GGGGGG [10]29NO2007 - - 5389.00 5211.00 5674.00 5269.95
5265 13869.14 5143.90
[11]BBBBBB [12]GGGGGG [13]25OC200 [14]CE [15]5600.00 74.00 15.00
168.60 34.05 810 2281.01 5143.90
[16]AAAAA [17]GGGGGG [18]27DE200 - - 5410.00 5125.00 5664.05 5265.00
694 1828.64 5143.90

[243]Top

[1]http://www.google.com/
[2]http://www.google.com/
[7]http://www.google.com/
[79]http://www.yahoo.com/
[2447]http://www.google.com/
[700]http://www.yahoo.com/

but this program saying some errors like

Quote:

simple.c:9: warning: unknown escape sequence '\}'
simple.c:9: warning: unknown escape sequence '\]'

i wanna output in a string "bb".

please help me

thank you in advance

SciYro · 10-18-2007, 03:14 AM

Since you just want to call other programs, why not just use shell scripting?

Also, im not sure you can pipe programs together like that, and im fairly sure that i see various shell commands within that command you are issuing, so i doubt it will ever run in C. Also, bb is not a string, but a single character.

And those errors seem to be coming from the compiler trying to compile that script, who knows what the compiler will make of it. Just use regular shell scripts instead, save yourself the trouble of debugging that.

ta0kira · 10-18-2007, 07:33 AM

You need to escape the escape chars: use \\[ instead of \[. This forces the compiler to use the \ character rather than interpreting it (such as \n.)

BTW, you aren't really writing a C program. It's shell wrapped with C, which is just sent to a shell anyway.
ta0kira

indienick · 10-18-2007, 09:17 AM

If you wanted to be really hardcore, you could write out the function of each piped program you call in the system() function.

I have a copy of The C Programming Language by Kernighan & Ritchie, and over the first few chapters you learn how to make a program that does exactly this. Of course, it takes a bit of extra typing to get the functionality you are requesting of those other programs, but the fact is you learn HOW TO DO IT!

ta0kira · 10-18-2007, 12:16 PM

Well if you're going that far you might as well use forks and execs and avoid the shell altogether...
ta0kira

indienick · 10-19-2007, 11:59 PM

Which really makes me wonder why a script would be written in C, when the exact same script could be written in the locally-installed shell. Execution time shouldn't be anything to worry about when it comes to something simple like this.

If you're going to learn C (just saying, keep in mind), I found the best way was to mostly everything yourself, instead of relying on pre-written/compiled commands.

I remember reading somewhere (I believe on this very forum) that use of the system() call was greatly frowned upon. *shrug*