Linux system programming: Write a cp command by yourself, linuxcp

Linux system programming: Write a cp command by yourself, linuxcp

Basic usage of the cp command: the target file of the cp source file

If the target file does not exist, create it. If yes, overwrite it.

Implementing a cp command is actually an operation to read and write files:

For source files: read all the content to the cache. The read function is used.

For the target file: write all the content in the cache to the target file. The function creat is used.

1/* ============================================== =========================================== 2 * Copyright (C) 2018. all rights reserved. 3*4 * file name: mycp. c 5 * Creator: ghostwu (Wu Hua) 6 * creation Date: July 7 * description: cp command to write 8*9 ==================================================== =============================== */10 11 # include <stdio. h> 12 # include <stdlib. h> 13 # include <sys/types. h> 14 # include <sys/stat. h> 15 # include <fcntl. h> 16 # include <unistd. H> 1718 # define COPYMODE 064419 # define BUF 409620 21 int main (int argc, char * argv []) 22 {23 if (argc! = 3) {24 printf ("usage: % s source destination \ n", argv [0]); 25 exit (-1 ); 26} 27 28 int in_fd =-1, out_fd =-1; 29 30 if (in_fd = open (argv [1], O_RDONLY) =-1) {31 perror ("file open"); 32 exit (-1); 33} 34 35 if (out_fd = creat (argv [2], COPYMODE )) =-1) {36 perror ("file copy"); 37 exit (-1); 38} 39 40 char n_chars [BUF]; 41 int len = 0; 42 43 while (len = read (in_fd, n_chars, size Of (n_chars)> 0) {44 if (write (out_fd, n_chars, len )! = Len) {45 printf ("file: % s copy error \ n", argv [2]); 46 exit (-1 ); 47} 48} 49 if (len =-1) {50 printf ("read % s file error \ n", argv [1]); 51 exit (-1 ); 52} 53 54 if (close (in_fd) =-1) {55 printf ("failed to close file % s \ n", argv [1]); 56 exit (-1); 57} 58 if (close (out_fd) =-1) {59 printf ("failed to close file % s \ n ", argv [2]); 60 exit (-1); 61} 62 63 return 0; 64}View Code