Operating System

copy command linux API

CP command

The cp command in Linux is used to copy files and directories. The cp command is part of the GNU coreutils package and is available on most Linux distributions.

The cp command syntax is as follows:

cp [OPTION]... SOURCE DEST

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

#define BUFFER_SIZE 4096

int main(int argc, char *argv[]) {
    int src = open(argv[1], O_RDONLY);
    int dst = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, 0644);

    char buffer[BUFFER_SIZE];
    ssize_t nread;

    while ((nread = read(src, buffer, BUFFER_SIZE)) > 0) {
        write(dst, buffer, nread);
    }

    close(src);
    close(dst);

    return 0;
}

To compile and run the program, use the following commands(dont copy the $ sign, it represents the terminal prompt):

$ gcc cp.c -o cp
$ ./cp source.txt destination.txt

There should be a file named source.txt and destination.txt in the same directory as the program.

Questions

What is the use of the cp command?

The cp command is used to copy files and directories in Linux.

What are the options available with the cp command?

The cp command has several options that can be used to modify its behavior. Some of the common options are:

• -r: Copy directories recursively
• -i: Prompt before overwriting
• -v: Verbose output

How can you copy a directory using the cp command?

To copy a directory and its contents, you can use the -r option with the cp command. For example:

cp -r source_dir destination_dir

What is the difference between the cp command and the mv command?

The cp command is used to copy files and directories, while the mv command is used to move files and directories. When you copy a file, the original file remains intact, while moving a file removes it from its original location.

What is the use of the open system call in the program?

The open system call is used to open a file for reading or writing. In the program, we use the open system call to open the source and destination files.

What is the use of the read and write system calls in the program?

The read system call is used to read data from a file descriptor, and the write system call is used to write data to a file descriptor. In the program, we use the read and write system calls to copy data from the source file to the destination file.