Answer:
See the lseek_example.c file. Modify the lseek_example.c, such that it reads from an input file (named "start.txt") and will print to an output file (named "end.txt") every (1+3*i)th character, starting from the 1st character in the input file. In other words, it will print the 1st character, then skip 2 characters and print the 4th one, then skip 2 characters and print the 7th one, and so on.
For instance, for input file:
ABCDEFGHIJKLM
It will output:
ADGJM
Iseek_example.c file contant:
// C program to read nth byte of a file and
// copy it to another file using lseek
#include
#include
#include
#include
void func(char arr[], int n)
{
// Open the file for READ only.
int f_read = open("start.txt", O_RDONLY);
// Open the file for WRITE and READ only.
int f_write = open("end.txt", O_WRONLY);
int count = 0;
while (read(f_read, arr, 1))
{
// to write the 1st byte of the input file in
// the output file
if (count < n)
{
// SEEK_CUR specifies that
// the offset provided is relative to the
// current file position
lseek (f_read, n, SEEK_CUR);
write (f_write, arr, 1);
count = n;
}
// After the nth byte (now taking the alternate
// nth byte)
else
{
count = (2*n);
lseek(f_read, count, SEEK_CUR);
write(f_write, arr, 1);
}
}
close(f_write);
close(f_read);
}
// Driver code
int main()
{
char arr[100];
int n;
n = 5;
// Calling for the function
func(arr, n);
return 0;
}
Explanation:
