#ifndef lint static char *sccsid = "@(#)getwd.c 4.2 (ULTRIX) 9/11/90"; #endif lint /************************************************************************ * * * Copyright (c) 1986 by * * Digital Equipment Corporation, Maynard, MA * * All rights reserved. * * * * This software is furnished under a license and may be used and * * copied only in accordance with the terms of such license and * * with the inclusion of the above copyright notice. This * * software or any other copies thereof may not be provided or * * otherwise made available to any other person. No title to and * * ownership of the software is hereby transferred. * * * * This software is derived from software received from the * * University of California, Berkeley, and from Bell * * Laboratories. Use, duplication, or disclosure is subject to * * restrictions under license agreements with University of * * California and with AT&T. * * * * The information in this software is subject to change without * * notice and should not be construed as a commitment by Digital * * Equipment Corporation. * * * * Digital assumes no responsibility for the use or reliability * * of its software on equipment which is not supplied by Digital. * * * ************************************************************************/ /************************************************************************ * Modfication History * * * * David L. Ballenger, 17-Jul-1984 * * 0001 Check status after calls to stat() and fstat() and return the * * appropriate error message if an error occured. * * * ************************************************************************/ /* * getwd() returns the pathname of the current working directory. On error * an error message is copied to pathname and null pointer is returned. */ #include #include #include #define CURDIR "." #define GETWDERR(s) errmsg(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 */ char *errmsg(); /* sets up error message */ 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 */ extern int errno ; /* error status from stat() and * fstat() */ extern *sys_errlist[] ; /* error messages for errno */ pathsize = 0; *pnptr = '\0'; /* Obtain info about the root and save the device and inode * information. */ if (stat(ROOTDIR, &d) != 0) { GETWDERR(sys_errlist[errno]); return(NULL) ; } rdev = d.st_dev; rino = d.st_ino; /* Climb back up the directory tree to the root, building up the * pathname as we go. */ for (;;) { /* Get info about the current directory, and get out of * the loop if we've reached the root. */ if (stat(CURDIR, &d) !=0) { GETWDERR(sys_errlist[errno]); goto fail; } if (d.st_ino == rino && d.st_dev == rdev) break; /* reached root directory */ /* Open the parent directory */ if ((dirp = opendir(PARENTDIR)) == NULL) { GETWDERR("can't open .."); goto fail; } /* Change the working directory to the parent */ if (chdir(PARENTDIR) < 0) { GETWDERR("can't chdir to .."); goto fail; } /* See if the PARENTDIR and CURDIR are on same device. */ if (fstat(dirp->dd_fd, &dd) != 0) { GETWDERR(sys_errlist[errno]); goto fail; } if (d.st_dev == dd.st_dev) { /* If the parent and root have the same dev #, we * may be at the root. */ if (d.st_ino == dd.st_ino) { /* reached root directory */ closedir(dirp); break; } /* Not at the root directory, so search for the * CURDIR directory entry. */ do { if ((dir = readdir(dirp)) == NULL) { GETWDERR("read error in .."); closedir(dirp); goto fail; } } while (dir->d_ino != d.st_ino); } else /* Search for the CURDIR directory entry, but now * we have to do a stat() call for each entry to * check the device. */ do { if((dir = readdir(dirp)) == NULL) { GETWDERR("read error in .."); closedir(dirp); goto fail; } if (stat(dir->d_name, &dd) != 0) { /* if stat failed, set impossible values into structure so that the test will fail and the loop will continue */ dd.st_ino = 0; dd.st_dev = 0; } } while(dd.st_ino != d.st_ino || dd.st_dev != d.st_dev); /* Put the CURDIR's name from the directory entry on the path. */ pnptr = prepend(PATHSEP, prepend(dir->d_name, pnptr)); closedir(dirp); /* release resources after the copy */ } if (*pnptr == '\0') /* current dir == root dir */ strcpy(pathname, ROOTDIR); else { strcpy(pathname, pnptr); if (chdir(pnptr) < 0) { GETWDERR("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); } /* * errmsg() formats the error message to be returned by getwd() */ static char * errmsg(buffer,msg) char *buffer ; char *msg; { strcat(strcpy(buffer,"getwd: "),msg) ; }
