report real path even if a symlink to a root dir comes first

[unix-history] / usr / src / lib / libc / gen / getcwd.c

/*      @(#)getcwd.c    4.9     (Berkeley)      %G%     */

/*
* getwd() returns the pathname of the current working directory. On error
* an error message is copied to pathname and null pointer is returned.
*/
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/dir.h>

#define CURDIR          "."
#define GETWDERR(s)     strcpy(pathname, (s));
#define PARENTDIR       ".."
#define PATHSEP         "/"
#define ROOTDIR         "/"

char *strcpy();
static int pathsize;                    /* pathname length */

char *
getwd(pathname)
       char *pathname;
{
       char pathbuf[MAXPATHLEN];               /* temporary pathname buffer */
       char *pnptr = &pathbuf[(sizeof pathbuf)-1]; /* pathname pointer */
       char *prepend();                /* prepend dirname to pathname */
       dev_t rdev;                     /* root device number */
       DIR *dirp;                      /* directory stream */
       ino_t rino;                     /* root inode number */
       struct direct *dir;             /* directory entry struct */
       struct stat d ,dd;              /* file status struct */

       pathsize = 0;
       *pnptr = '\0';
       stat(ROOTDIR, &d);
       rdev = d.st_dev;
       rino = d.st_ino;
       for (;;) {
               stat(CURDIR, &d);
               if (d.st_ino == rino && d.st_dev == rdev)
                       break;          /* reached root directory */
               if ((dirp = opendir(PARENTDIR)) == NULL) {
                       GETWDERR("getwd: can't open ..");
                       goto fail;
               }
               if (chdir(PARENTDIR) < 0) {
                       GETWDERR("getwd: can't chdir to ..");
                       goto fail;
               }
               fstat(dirp->dd_fd, &dd);
               if (d.st_dev == dd.st_dev) {
                       if (d.st_ino == dd.st_ino) {
                               /* reached root directory */
                               closedir(dirp);
                               break;
                       }
                       do {
                               if ((dir = readdir(dirp)) == NULL) {
                                       closedir(dirp);
                                       GETWDERR("getwd: read error in ..");
                                       goto fail;
                               }
                       } while (dir->d_ino != d.st_ino);
               } else
                       do {
                               if((dir = readdir(dirp)) == NULL) {
                                       closedir(dirp);
                                       GETWDERR("getwd: read error in ..");
                                       goto fail;
                               }
                               lstat(dir->d_name, &dd);
                       } while(dd.st_ino != d.st_ino || dd.st_dev != d.st_dev);
               closedir(dirp);
               pnptr = prepend(PATHSEP, prepend(dir->d_name, pnptr));
       }
       if (*pnptr == '\0')             /* current dir == root dir */
               strcpy(pathname, ROOTDIR);
       else {
               strcpy(pathname, pnptr);
               if (chdir(pnptr) < 0) {
                       GETWDERR("getwd: can't change back to .");
                       return (NULL);
               }
       }
       return (pathname);

fail:
       chdir(prepend(CURDIR, pnptr));
       return (NULL);
}

/*
* prepend() tacks a directory name onto the front of a pathname.
*/
static char *
prepend(dirname, pathname)
       register char *dirname;
       register char *pathname;
{
       register int i;                 /* directory name size counter */

       for (i = 0; *dirname != '\0'; i++, dirname++)
               continue;
       if ((pathsize += i) < MAXPATHLEN)
               while (i-- > 0)
                       *--pathname = *--dirname;
       return (pathname);
}