Question

My question is listed the below please any help this assignment ;

There is a skeleton code:  copy_file_01.c

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

int main(int argc, char* argv[]) {
char ch ;
FILE *source , *target;

   if(argc != 3){
printf ("Usage: copy file1 file2");
exit(EXIT_FAILURE);
}

source = fopen(argv[1], "r");

if (source == NULL) {
printf("Press any key to exit...\n");
exit(EXIT_FAILURE);
}

target = fopen(argv[2], "w");

if (target == NULL) {
fclose(source);
printf("Press any key to exit...\n");
exit(EXIT_FAILURE);
}

while ((ch = fgetc(source)) != EOF)
fputc(ch, target);

printf("File copied successfully.\n");

fclose(source);
fclose(target);

return 0;
}

hw1 using system calls

The following program copies input file *argc[1] to output file *argc[2]. For file access the following C library functions are used:

FILE * fopen ( const char * filename, const char * mode );

int fclose ( FILE * stream );
int fgetc ( FILE * stream );
int fputc ( int character, FILE * stream );

re-write copy_file_01.c program using linux system calls  replacing the functions which are listed above.

this web page  is useful: 

https://www.geeksforgeeks.org/input-output-system-calls-c-create-open-close-read-write/

Answer 1

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>

#define BUFF_SIZE 1024

int main(int argc, char* argv[])
{
    int sourceFD,destinationFD,nbread,nbwrite;
    char *buff[BUFF_SIZE];
    
    /*Check if both src & dest files are received */
    if(argc != 3 )
    {
        printf("\nUsage: file1 file2\n");
        exit(EXIT_FAILURE);
    }

    /*Open source file*/
    sourceFD = open(argv[1],O_RDONLY);

    if(sourceFD == -1)
    {
        printf("\nError opening file 1 \n");
        exit(EXIT_FAILURE);    
    }
    
    /*Open destination file with respective flags & modes*/
    destinationFD = open(argv[2],O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);

    if(destinationFD == -1)
    {
        printf("\nError opening file 2   \n");
        exit(EXIT_FAILURE);
    }

    /*Start data transfer from src file to dest file till it reaches EOF*/
    while((nbread = read(sourceFD,buff,BUFF_SIZE)) > 0)
    {
        if(write(destinationFD,buff,nbread) != nbread)
            printf("\nError in writing data to %s\n",argv[2]);
    }
    
    if(nbread == -1)
        printf("\nError in reading data from %s\n",argv[1]);
    
    if(close(sourceFD) == -1)
        printf("\nError in closing file %s\n",argv[1]);

    if(close(destinationFD) == -1)
        printf("\nError in closing file %s\n",argv[2]);

    exit(EXIT_SUCCESS);
}

//ouput