use syscall for doing syswrite stuff -- more portable?

[unix-history] / usr / src / local / sccscmds / sccscmds.2 / util / curdir.c

/*
* SCCSID(@(#)curdir.c  4.5);
*/
#include        <sys/param.h>
#include        <sys/stat.h>
#include        <sys/dir.h>

#define dot     "."
#define dotdot  ".."

static  char    *name;

static  int     off;
static  struct  stat    d, dd;
static  struct  direct  *dir;
static  DIR     *dirp;
static  int     cat(), prexit();

char *
curdir(np)
char *np;
{
       int rdev, rino;

       off = -1;
       *np++ = '/';
       name = np;
       stat("/", &d);
       rdev = d.st_dev;
       rino = d.st_ino;
       for (;;) {
               stat(dot, &d);
               if (d.st_ino==rino && d.st_dev==rdev)
                       goto done;
               if ((dirp = opendir(dotdot)) == 0)
                       prexit("curdir: cannot open ..\n");
               fstat(dirp->dd_fd, &dd);
               chdir(dotdot);
               if(d.st_dev == dd.st_dev) {
                       if(d.st_ino == dd.st_ino)
                               goto done;
                       do
                               if ((dir = readdir(dirp)) == 0)
                                       prexit("curdir: read error in ..\n");
                       while (dir->d_ino != d.st_ino);
               } else
                       do {
                               if ((dir = readdir(dirp)) == 0)
                                       prexit("curdir: read error in ..\n");
                               stat(dir->d_name, &dd);
                       } while(dd.st_ino != d.st_ino || dd.st_dev != d.st_dev);
               closedir(dirp);
               cat();
       }
done:
       name--;
       if (chdir(name) < 0) {
               write(2, name, strlen(name));
               prexit(": can't change back\n");
       }
       return (0);
}

static
cat()
{
       register i, j;

       i = dir->d_namlen;
       if ((off+i+2) > 1024-1)
               return;
       for(j=off+1; j>=0; --j)
               name[j+i+1] = name[j];
       if (off >= 0)
               name[i] = '/';
       off += i+1;
       name[off] = 0;
       for(--i; i>=0; --i)
               name[i] = dir->d_name[i];
}

static
prexit(cp)
char *cp;
{
       write(2, cp, strlen(cp));
       exit(1);
}