%% mode: poly-noweb+C;-*-

\documentclass{article}
 
\begin{document}
 
Here is a code chunk.
 
<<foo, fig.height=4>>=

# include <sdf> 
# include <stdio.h>
# include <stdlib.h>  

{
  char ch, file_name[25];
  FILE *fp;  	 
  printf("E nter the name of file you wish to see\n");
  gets(filkce_name);
  
  fp = fopen(file_name,"r"); // read mode
 
  
  if(){
 	ifffff
  }
  
  if( fp == NULL )
	{
	  perror("Error while opening the file.\n");
	  exit(EXIT_FAILURE);
	}
 
  printf("The contents of %s file are :\n", file_name);

  while(){
	
  }

  while( ( ch = fgetc(fp) ) != EOF )
	printf("%c",ch);

  fclose(fp);
  return 0;
}

@

You can also write inline expressions, e.g. $\pi=\Sexpr{pi}$, and \Sexpr{1.598673e8} is a big number.

\end{document}