Programming

for(int z=0;z<2;z++)
{
fp=fopen("poly.dat","r");

/*do something which reads this file into a 2D array*/

fclose(fp);

fp=fopen("poly.dat","w");
/*do something which writes into this file*/

fclose(fp);

printf("\n***********************\n");
}


*** glibc detected *** ./a.out: malloc(): memory corruption: 0x09f901b0 *** 
======= Backtrace: ========= 
/lib/tls/i686/cmov/libc.so.6[0xb7747376] 
/lib/tls/i686/cmov/libc.so.6(__libc_malloc+0x95)[0xb7748ac5] 
/lib/tls/i686/cmov/libc.so.6[0xb7734acf] 
/lib/tls/i686/cmov/libc.so.6(fopen+0x2c)[0xb7734b9c] 
./a.out[0x8048807] 
/lib/tls/i686/cmov/libc.so.6(__libc_start_main+0xe5)[0xb76eb775] 
./a.out[0x8048621] 
======= Memory map: ======== 
08048000-0804a000 r-xp 00000000 08:05 6619566    /home/dare/Desktop/a.out 
0804a000-0804b000 r--p 00001000 08:05 6619566    /home/dare/Desktop/a.out 
0804b000-0804c000 rw-p 00002000 08:05 6619566    /home/dare/Desktop/a.out 
09f90000-09fb1000 rw-p 09f90000 00:00 0          [heap] 
b7500000-b7521000 rw-p b7500000 00:00 0  
b7521000-b7600000 ---p b7521000 00:00 0  
b76b6000-b76c3000 r-xp 00000000 08:05 7225409    /lib/libgcc_s.so.1 
b76c3000-b76c4000 r--p 0000c000 08:05 7225409    /lib/libgcc_s.so.1 
b76c4000-b76c5000 rw-p 0000d000 08:05 7225409    /lib/libgcc_s.so.1 
b76d4000-b76d5000 rw-p b76d4000 00:00 0  
b76d5000-b7831000 r-xp 00000000 08:05 7242659    /lib/tls/i686/cmov/libc-2.9.so 
b7831000-b7832000 ---p 0015c000 08:05 7242659    /lib/tls/i686/cmov/libc-2.9.so 
b7832000-b7834000 r--p 0015c000 08:05 7242659    /lib/tls/i686/cmov/libc-2.9.so 
b7834000-b7835000 rw-p 0015e000 08:05 7242659    /lib/tls/i686/cmov/libc-2.9.so 
b7835000-b7838000 rw-p b7835000 00:00 0  
b7842000-b7849000 rw-p b7842000 00:00 0  
b7849000-b784a000 r-xp b7849000 00:00 0          [vdso] 
b784a000-b7866000 r-xp 00000000 08:05 7225754    /lib/ld-2.9.so 
b7866000-b7867000 r--p 0001b000 08:05 7225754    /lib/ld-2.9.so 
b7867000-b7868000 rw-p 0001c000 08:05 7225754    /lib/ld-2.9.so 
bfb3e000-bfb53000 rw-p bffea000 00:00 0          [stack] 
Aborted

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

	int random_no(int);
	void calc_file_row_col(FILE *,int *,int *);

	int main()
	{
	int i,j,z;
	int temp=0;
	int row,column;

	FILE *fp;
	char x,**a;

	for(z=0;z<2;++z){
	fp=fopen("poly.dat","r");
	
	calc_file_row_col(fp,&row,&column);     //Function which calculates 
                                                      // the no of rows and column of a file
	
        a=calloc(row,sizeof(char *));			// Declare a 2D array of size 
                                                                // row by column   
	for(i=0;i<row;i++)
		a[i]=calloc(column,sizeof(char));

	for(i=0;i<row;i++)				//  Read the elements of file fp into 
		{                                      //  array a
		for(j=0;j<column+1;j++)
			{
			x=getc(fp);
			if(x=='\n')
			{}
			else
			{
			*(*(a+i)+j)=x;
			}
		}}

	fclose(fp);
	fseek(fp,0,SEEK_SET);

	temp=random_no(row);			// Generates a random no. between 0 and row
	printf("temp=%d\n",temp);

	fp=fopen("poly.dat","w");

	for(i=0;i<temp;i++)		//Write elements from 0 to temp and then temp to row in file fp; 
		{
		for(j=0;j<column;j++)
			fprintf(fp,"%c",a[i][j]);

	fprintf(fp,"\n");
	}

	for(i=temp+1;i<row;i++)
		{
		for(j=0;j<column;j++)
			fprintf(fp,"%c",a[i][j]);

		fprintf(fp,"\n");
		}	

	fclose(fp);	

	for(i=0;i<row;i++)
	free(a[i]);

	free(a);
	a=NULL;
	}

	return 0;
	}

	int random_no(int range)
	{
	int LOW=0;							
	int r;						
	time_t seconds;                                 
	time(&seconds);                                 
	srand((unsigned int)seconds);                                       
	r = rand() % (range - LOW + 1) + LOW;                       
	return r%range;
	}

	void calc_file_row_col(FILE *poly,int *row,int *column)
	{
	int m=0;
	int n=0;
	char x;
	fseek(poly,0,SEEK_SET);
	while((x=getc(poly))!=EOF)
	{
	if(x=='\n'){
		m++;
		n=0;
		}
	else{
		n++;
		*column=n;
		}
	}
	*row=m;
	printf("row=%d column=%d\n",*row,*column);
	fseek(poly,0,SEEK_SET);
	}

	00132404 
	00013240 
	00001324 
	a0000132 
	16000013 
	53200001 
	05460000 
	4061a000 
	24062a00 
	32406fe0 
	132407aa 
	0132407d 
	13240860 
	00013240 
	00001324 
	e0000132