linux之getcwd函数解析

[lingyun@localhost getcwd]$ cat getcwd.c
/*********************************************************************************
 *      Copyright:  (C) 2013 fulinux<[email protected]> 
 *                  All rights reserved.
 *
 *       Filename:  getcwd.c
 *    Description:  This file 
 *                 
 *        Version:  1.0.0(08/06/2013~)
 *         Author:  fulinux <[email protected]>
 *      ChangeLog:  1, Release initial version on "08/06/2013 03:56:30 PM"
 *                 
 ********************************************************************************/


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


int main(void)
{
    char *ptr;
    int size = 50;
    if(chdir("/usr/tmp/yum-lingyun-sYjnfB") < 0)
    {
        perror("chdir");
        exit(1);
    }
    ptr = malloc(size);


    if(getcwd(ptr, size) == NULL)
    {
        perror("getcwd");
        exit(1);
    }


    printf("cwd = %s\n", ptr);
    exit(0);


}
[lingyun@localhost getcwd]$ ll /usr/
total 224
dr-xr-xr-x.   2 root root 69632 Apr 29 03:32 bin
drwxr-xr-x.   2 root root  4096 Sep 23  2011 etc
drwxr-xr-x.   2 root root  4096 Sep 23  2011 games
drwxr-xr-x.  39 root root  4096 Apr 15 15:44 include
dr-xr-xr-x.  29 root root  4096 Apr 22 03:18 lib
dr-xr-xr-x. 132 root root 86016 Apr 29 03:32 lib64
drwxr-xr-x.  30 root root 12288 Apr 29 03:32 libexec
drwxr-xr-x.  15 root root  4096 Jun  5 19:57 local
drwxr-xr-x    3 root root  4096 Apr 21 20:38 man
dr-xr-xr-x.   2 root root 12288 Jul 30 03:42 sbin
drwxr-xr-x. 265 root root 12288 Jun  9 09:34 share
drwxr-xr-x.   4 root root  4096 Jul  6  2012 src
lrwxrwxrwx.   1 root root    10 Jul  6  2012 tmp -> ../var/tmp
[lingyun@localhost getcwd]$ ls /usr/tmp/yum-lingyun-sYjnfB/
[lingyun@localhost getcwd]$ gcc getcwd.c 
[lingyun@localhost getcwd]$ ./a.out 
cwd = /var/tmp/yum-lingyun-sYjnfB
[lingyun@localhost getcwd]$