1 #include <unistd.h>
2
3 char *getcwd(char *cwdbuf, size_t size);

  1 /*2  * =====================================================================================3  *4  *       Filename:  18.5.c5  *6  *    Description:  7  *8  *        Version:  1.09  *        Created:  2014年05月11日 14时04分35秒10  *       Revision:  none11  *       Compiler:  gcc12  *13  *         Author:  alan (), alan19920626@gmail.com14  *   Organization:  15  *16  * =====================================================================================17  */18 19 #include <sys/stat.h>20 #include <fcntl.h>21 #include <dirent.h>22 #include <sys/types.h>23 #include "tlpi_hdr.h"24 25 #define BUF_MAX 409626 27 extern int errno; 28 29 char *Getcwd(char *cwdbuf, size_t size){30     char path[BUF_MAX], cwd[BUF_MAX];31     DIR *dirp;32     struct dirent *dp;33     struct stat sb, sb_d, sb_1;34     dev_t dev;35     ino_t ino;36 37     while(1){38         //获取当前目录的文件信息39         if(stat(".", &sb) == -1)40             errExit("stat");41         dev = sb.st_dev;42         ino = sb.st_ino;43 44         //获取父目录的对应的目录流和父目录的文件信息45         if((dirp = opendir("..")) == NULL)46             errExit("opendir");47         if(stat("..", &sb_1) == -1)48             errExit("stat");49 50         //判断当前目录是否与父目录相同51         if(sb_1.st_dev == dev && sb_1.st_ino == ino)52             break;53 54         errno = 0;55         56         //在父目录对应的目录流读取条目57         while((dp = readdir(dirp)) != NULL){58             snprintf(path, BUF_MAX, "../%s", dp->d_name);59 60             if(stat(path, &sb_d) == -1)61                 errExit("stat");62 63             //得到当前目录对应的条目并将目录逐渐完善64             if(dev == sb_d.st_dev && ino == sb_d.st_ino){65                 memset(cwd, 0, sizeof(cwd));66                 if(strcat(cwd, "/") == NULL)67                     errExit("strcat");68                 if(strcat(cwd, dp->d_name) == NULL)69                     errExit("strcat");70                 if(strcat(cwd, cwdbuf) == NULL)71                     errExit("strcat");72 73                 if(strncpy(cwdbuf, cwd, BUF_MAX) == NULL)74                     errExit("strncpy");75                 break;76             }77             78         }79 80         if(dp == NULL && errno != 0)81             errExit("readdir");82 83         closedir(dirp);84         chdir("..");      //改变当前目录85     }86 87     return cwdbuf;88 }89 90 int main(int argc, char *argv[]){91     char buf[BUF_MAX];92     char t_buf[BUF_MAX];93     char *p;94     int fd;95 96     if((fd = open(".", O_RDONLY)) == -1)97         errExit("open");98 99     if(argc != 1)
100         usageErr("%s", argv[0]);
101
102     p = Getcwd(buf, BUF_MAX);
103     if(p == NULL)
104         errExit("My getcwd");
105     printf("My getcwd: %s\n", p);
106     fchdir(fd);    //遣回最初的目录
107
108     p = getcwd(t_buf, BUF_MAX);
109     if(p == NULL)
110         errExit("getcwd");
111     printf("getcwd: %s\n", p);
112
113     exit(EXIT_SUCCESS);
114 }

lancelot@debian:~/Code/tlpi$ pwd
/home/lancelot/Code/tlpi
lancelot@debian:~/Code/tlpi$ ./18.5
My getcwd: /home/lancelot/Code/tlpi
getcwd: /home/lancelot/Code/tlpi

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