2. Write programs using the I/O system calls of UNIX/LINUX operating system(open,
read, write, close, fcntl, seek, stat, opendir, readdir)
Program:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
int main() {
// Open a source file for reading
int source_fd = open("source.txt", O_RDONLY);
if (source_fd == -1) {
perror("Failed to open source.txt");
exit(1);
}
// Create or open a destination file for writing
int dest_fd = open("destination.txt", O_WRONLY | O_CREAT | O_TRUNC, 0644);
if (dest_fd == -1) {
perror("Failed to open destination.txt");
close(source_fd); // Close the source file
exit(1);
}
// Read from the source file and write to the destination file
char buffer[4096]; // A buffer to hold data
ssize_t nread;
while ((nread = read(source_fd, buffer, sizeof(buffer))) > 0) {
if (write(dest_fd, buffer, nread) != nread) {
perror("Write error");
break;
}
}
// Check if there was an error during reading
if (nread < 0) {
perror("Read error");
}
// Close both files
close(source_fd);
close(dest_fd);
return 0;
}
Explanation:
In this program, we use the following system calls:
Open : Opens files.
Read : Reads data from a file.
Write : Writes data to a file.
Close : Closes open files.
Perror : Prints error messages.
Fcntl : A system call for file control is not used in this example but is available for other file
operations.
Seek Stat : File seeking operations are not used in this basic example.
: File stat functions are not used here.
Opendir Readdir : Opening directories is not used in this example.
: Reading directories is not used in this example.