Supports real-time file updates in C language and real-time updates in C language.

Supports real-time file updates in C language and real-time updates in C language.

I. Introduction

In a linux or unix operating system, many services are enabled during system boot. These services are called daemon processes. The daemon is disconnected from the terminal and runs in the background: the daemon is separated from the terminal to prevent the information in the execution process from being displayed on any terminal and the process is not interrupted by any terminal information generated by any terminal. This document describes how to update files in real time using a daemon.

 

Ii. Source Code

File 1: Realtime_Update.c

# Include <stdio. h> # include <stdlib. h> # include <unistd. h> # include <time. h> # include <fcntl. h> # include <sys/stat. h> void init_daemon (void); static inline int timespec_compare (const struct timespec * lhs, const struct timespec * rhs);/*** file update Real-Time Detection Program */main () {int ret; struct stat statbuff_file1; struct stat statbuff_file2; char * file1 = "~ /Test_file1.txt "; char * file2 = "~ /Test_file2.txt "; stat (file1, & statbuff_file1); stat (file2, & statbuff_file2); // initialize to Daemon init_daemon (); // execute cyclically, once every second while (1) {// determine whether the file is updated with ret = timespec_compare (& statbuff_file1.st_mtim, & statbuff_file2.st_mtim); if (ret> 0) {system ("cp-~ /Test_file1.txt ~ /Test_file2.txt ");} sleep (1); // sleep for one second}/*** lhs <rhs: return <0 * lhs = rhs: return 0 * lhs> rhs: return> 0 */static inline int timespec_compare (const struct timespec * lhs, const struct timespec * rhs) {if (lhs-> TV _sec <rhs-> TV _sec) return-1; if (lhs-> TV _sec> rhs-> TV _sec) return 1; return lhs-> TV _nsec-rhs-> TV _nsec ;}

File 2: init. c

# Include <stdlib. h> # include <unistd. h> # include <signal. h> # include <sys/param. h> # include <sys/types. h> # include <sys/stat. h> void init_daemon (void) {int pid; int I; if (pid = fork () exit (0); // It is the parent process, stop the parent process else if (pid <0) exit (1); // fork failed, exit // is the first sub-process, and the background continues to execute setsid (); // The first sub-process becomes the new session leader and process leader // and is separated from the control terminal if (pid = fork () exit (0); // is the first sub-process, stop the first sub-process else if (pid <0) exit (1); // fork failed, exit // is the second sub-process, continue // the second sub-process is no longer the session leader for (I = 0; I <NOFILE; ++ I) // close the opened file descriptor close (I ); chdir ("/tmp"); umask (0); // reset the file creation mask return ;}

Compile

gcc -o Realtime_Update init.c  Realtime_Update.c

Run

./Realtime_Update

 

3. Download source code

http://files.cnblogs.com/files/274914765qq/Realtime_Update_Daemon.zip

 

Reference: http://www.cnblogs.com/274914765qq/p/4792707.html