将内容从一个文件复制到另一个文件

Question

在linux平台（ubuntu）上编写一个将内容从一个文件复制到另一个文件的程序，或者创建一个在ubuntu中复制文件的程序

Answer 1

I would look into using redirection and pipes like you would with a Shell? this example below was from a shell I wrote, this is specifically the redirect function. (>>) so you could do file1 >> file2 and it would copy the contents of one file to another. the

open(file[0], O_RDWR | O_CREAT, 0666); and while ((count = read(0, &c, 1)) > 0)
          write(fd, &c, 1)

; //Write to file are the important parts

void redirect_cmd(char** cmd, char** file) {
  int fds[2]; // file descriptors
  int count;  // used for reading from stdout
  int fd;     // single file descriptor
  char c;     // used for writing and reading a character at a time
  pid_t pid;  // will hold process ID; used with fork()

  pipe(fds);


  if (fork() == 0) {
    fd = open(file[0], O_RDWR | O_CREAT, 0666);
    dup2(fds[0], 0);
    close(fds[1]);

    // Read from stdout
    while ((count = read(0, &c, 1)) > 0)
      write(fd, &c, 1); //Write to file

    exit(0);

  //Child1
  } else if ((pid = fork()) == 0) {
    dup2(fds[1], 1);

    //Close STDIN
    close(fds[0]);

    //Output contents
    execvp(cmd[0], cmd);
    perror("execvp failed");

  //Parent
  } else {
    waitpid(pid, NULL, 0);
    close(fds[0]);
    close(fds[1]);
  }
}

Answer 2

The General IDEA

• Open one file using fopen
• Open a Second File using fopen
• Read from the first file using fread

• Write to the Second File use fwrite

• You can substitute scanf for fread and, fprintf for fwrite if you need to write formated data.

Answer 3

You didn't specify what programming language must be used. So, I'll assume you're using bash. Write a script that uses the cp command and your assignment is solved.