copying a portion of Binary file into another Binary file

vishi · #1 23-Jul-2005, 23:18

Hi friends,
I have got a binary file with large no of records. I have to copy a portion of that file in another binary file.I am trying to read from the first one and write into the second oneusing for loop for certain no. of records but its not working. Can I do like this?Can anyone help me out?

nkhambal · #2 24-Jul-2005, 01:53

Quote:

Originally Posted by vishi

Can I do like this?Can anyone help me out?

Yes, you can do it that way.

May be you could post the code you have written so far for copying with the problem that you are facing with it.

kobi_hikri · #3 24-Jul-2005, 04:33

Quote:

Originally Posted by vishi

I am trying to read from the first one and write into the second oneusing for loop for certain no. of records but its not working. Can I do like this?

Just a short example :

CPP / C++ / C Code:

char current_line[256];
//Change this to the number of lines you wish to read.
int   max_lines = 100;
int   current_line = 0;
FILE *ifp;
ifp = fopen("x.y","r");
if (ifp != NULL)
   while (fgets(current_line,256,ifp) && (current_line < max_lines))
      {
         //Do your stuff here.
         current_line++;
      }

This is the basic idea. Post your code and errors for further help.

Best regards,
Kobi.

nkhambal · #4 24-Jul-2005, 06:01

I wrote this file copy program a while back using low-level I/O functions creat(), open(), read() and write(). Source file is read in chunks of predefined size and written into the new file. New file, if not available is created by the program.

CPP / C++ / C Code:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <ctype.h>
#include <fcntl.h>
#include <sys/stat.h>

int main(int argc, char *argv[])
{
        if (argc!=3)
        {
                printf("\nUSAGE: %s <source file name> <destination file name>\n",argv[0]);
                exit(1);
        }

        int src_handle,dst_handle;
        char buffer[512];
        const int bytes_read=512;
        int rd,wr,bytes_copied;
        struct stat file_attr;
        int file_exist=0;
        int overwrite=0;
        char line[10];
        char choice[5];
        char ch;

        /* Read source file attributes */
        if ((stat(argv[1],&file_attr))<0)
        {
                perror("Stat Error");
        }

        /* Open Source file for reading */
        if ((src_handle=open(argv[1],O_RDONLY))==-1)
        {
                perror("Source File open read");
                exit(1);
        } 

        /* Open/Create destination file for reading */
    if ((dst_handle=open(argv[2],O_WRONLY))!=-1)
    {
                /* File already exists */
                file_exist=1;
    } else {
                        if ((dst_handle=creat(argv[2],00666))==-1)
                        {
                                perror("Destination File create");
                                exit(1);
                        } 
                        if ((dst_handle=open(argv[2],O_WRONLY))==-1)
                        {
                                perror("Destination File open write");
                                exit(1);
                        } 
        }

        //printf("\ncheck1 file_exist: %d Overwrite: %d \n", file_exist,overwrite);
        if (file_exist)
        {
                /* Check if user wants to overwrite */
                printf("Destination file exists.Overwrite?[Y]es/[N]o: ");
                fgets(line,sizeof(line),stdin);
                sscanf(line,"%s",choice);
                //printf("choice %c\n", choice);
                if ((strcasecmp(choice,"No")==0) || (strcasecmp(choice,"n")==0))
                {
                        ch='n';
                } else if ((strcasecmp(choice,"Yes")==0) || (strcasecmp(choice,"y")==0))
                {
                        ch='y';
                } else {
                        ch='n';
                }
                //choice=getchar();
                if (toupper(ch)=='Y')
                {
                        overwrite=1;
                }
        }

        if (overwrite || !(file_exist))
        {

                        memset(buffer,'\0',512);
                        bytes_copied=0;

                        /*Start copying*/
                        while ((rd=read(src_handle,buffer,bytes_read*(sizeof(char))))!=0)
                        {
                                //printf("\nrd:= %d\n",rd);
                                if (rd==-1)
                                {
                                        printf("\nError reading source file\n");
                                        exit(1);
                                }
                                printf("!");
                                bytes_copied+=rd;
                                wr=write(dst_handle,buffer,rd*(sizeof(char)));
                                //printf("\nwr:= %d\n",wr);
                                if (wr==-1)
                                {
                                        printf("\nError writing to destination file\n");
                                        exit(1);
                                }
                        }

                        if ((chmod(argv[2],file_attr.st_mode))<0)
                        {
                                perror("chmod error");
                        }
                        if ((chown(argv[2],file_attr.st_uid,file_attr.st_gid))<0)
                        {
                                perror("chown error");
                        }
                 printf("\n");
                 printf("%d bytes copied.\n",bytes_copied);
        } else {
                printf("File not copied.\n");
        }
 return 0;
}

I have tested this on linux.

Quote:

[root@linux snoopy]# ./fcopy intf1.c intf.c
!!!!!!!
3129 bytes copied.
[root@linux-outside snoopy]# ls -la intf*
-rwxr-xr-x 1 root root 13245 Jul 24 03:08 intf
-rw-r--r-- 1 snoopy snoopy 3129 Jul 24 03:45 intf1.c
-rw-r--r-- 1 snoopy snoopy 3129 Jul 24 03:59 intf.c
[root@linux snoopy]#

vishi · #5 24-Jul-2005, 23:27

I have written this code

CPP / C++ / C Code:

#include<stdio.h>
void main()
{
		struct Data
		{
		char name[4];
		int value[6];
		};
		struct Data person[5]={
			{"Aya",80},
			{"hUA",48},
			{"AdA",70},
			{"sTA",90},
		
		};

	FILE* fptr;
	FILE* sptr;
	fptr=fopen("C:/file","a+b");
	sptr=fopen("C:/gfile","a+b");
	fwrite(&person,sizeof(Data),1,fptr);

	while(feof(fptr))
	{
	fread(&person,sizeof(Data),1,fptr);
	fwrite(&person,sizeof(Data),1,sptr);
	fread(&person,sizeof(Data),1,fptr);
	}
	fclose(fptr);
	fclose(sptr);
}

But this is not working .somethimg else is getting written in the other file

Dave Sinkula · #6 25-Jul-2005, 09:05

http://www.eskimo.com/~scs/C-faq/q12.30.html

[edit]Why it's bad to use feof() to control a loop -- but you got it backwards anyway.

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copying a portion of Binary file into another Binary file

Try to give an example code.