recovery中快速导出log到文件(freopen)

recovery.cpp中log输出用recovery 实现.

大概样子如下：

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
static const char *TEMPORARY_LOG_FILE = "./temp.log";


int  main(int argc, char **argv) {
    time_t start = time(NULL);
    // If these fail, there's not really anywhere to complain...
    freopen(TEMPORARY_LOG_FILE, "a", stdout); setbuf(stdout, NULL);
    freopen(TEMPORARY_LOG_FILE, "a", stderr); setbuf(stderr, NULL);
    printf ("push me to log .\n");

    printf("current time is  %s \n", ctime(&start));
    system("echo 'push log \n' >> ./temp.log");
}

gcc -g -o pushtolog main.c

./pushtolog

可以看到temp.log文件内容如下：

printf 输出的所有内容，都到处到temp.log文件了，简单有方便。

 

可以看下帮助： man  freopen

       The freopen() function opens the file whose name is the string  pointed
       to by path and associates the stream pointed to by stream with it.  The
       original stream (if it exists) is closed.  The mode  argument  is  used
       just  as  in  the  fopen()  function.  The primary use of the freopen()
       function is to change the file associated with a standard  text  stream
       (stderr, stdin, or stdout).

       主要功能就是让标准输入输出流与文件相结合。