gcc/getpwd.c

   1 /* getpwd.c - get the working directory */
   2
   3 #include "config.h"
   4
   5 #include <errno.h>
   6 #include <sys/types.h>
   7 #include <sys/stat.h>
   8
   9 #ifndef errno
  10 extern int errno;
  11 #endif
  12
  13 /* Virtually every UN*X system now in common use (except for pre-4.3-tahoe
  14    BSD systems) now provides getcwd as called for by POSIX.  Allow for
  15    the few exceptions to the general rule here.  */
  16
  17 #if !(defined (POSIX) || defined (USG) || defined (VMS))
  18 #include <sys/param.h>
  19 extern char *getwd ();
  20 #define getcwd(buf,len) getwd(buf)
  21 #define GUESSPATHLEN (MAXPATHLEN + 1)
  22 #else /* (defined (USG) || defined (VMS)) */
  23 extern char *getcwd ();
  24 /* We actually use this as a starting point, not a limit.  */
  25 #define GUESSPATHLEN 100
  26 #endif /* (defined (USG) || defined (VMS)) */
  27
  28 char *getenv ();
  29 char *xmalloc ();
  30
  31 #ifndef VMS
  32
  33 /* Get the working directory.  Use the PWD environment variable if it's
  34    set correctly, since this is faster and gives more uniform answers
  35    to the user.  Yield the working directory if successful; otherwise,
  36    yield 0 and set errno.  */
  37
  38 char *
  39 getpwd ()
  40 {
  41   static char *pwd;
  42   static int failure_errno;
  43
  44   char *p = pwd;
  45   size_t s;
  46   struct stat dotstat, pwdstat;
  47
  48   if (!p && !(errno = failure_errno))
  49     {
  50       if (! ((p = getenv ("PWD")) != 0
  51              && *p == '/'
  52              && stat (p, &pwdstat) == 0
  53              && stat (".", &dotstat) == 0
  54              && dotstat.st_ino == pwdstat.st_ino
  55              && dotstat.st_dev == pwdstat.st_dev))
  56
  57         /* The shortcut didn't work.  Try the slow, ``sure'' way.  */
  58         for (s = GUESSPATHLEN;  ! getcwd (p = xmalloc (s), s);  s *= 2)
  59           {
  60             int e = errno;
  61             free (p);
  62             if (e != ERANGE)
  63               {
  64                 errno = failure_errno = e;
  65                 p = 0;
  66                 break;
  67               }
  68           }
  69
  70       /* Cache the result.  This assumes that the program does
  71          not invoke chdir between calls to getpwd.  */
  72       pwd = p;
  73     }
  74   return p;
  75 }
  76
  77 #else   /* VMS */
  78
  79 #ifndef MAXPATHLEN
  80 #define MAXPATHLEN 255
  81 #endif
  82
  83 char *
  84 getpwd ()
  85 {
  86   static char *pwd = 0;
  87
  88   if (!pwd) pwd = getcwd (xmalloc (MAXPATHLEN+1), MAXPATHLEN+1);
  89   return pwd;
  90 }
  91
  92 #endif  /* VMS */