| [9] | 1 | /* getcwd() - get the name of the current working directory.
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| 2 | * Author: Kees J. Bot
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| 3 | * 30 Apr 1989
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| 4 | */
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| 5 | #define nil 0
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| 6 | #define chdir _chdir
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| 7 | #define closedir _closedir
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| 8 | #define getcwd _getcwd
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| 9 | #define opendir _opendir
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| 10 | #define readdir _readdir
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| 11 | #define rewinddir _rewinddir
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| 12 | #define stat _stat
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| 13 | #include <sys/types.h>
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| 14 | #include <sys/stat.h>
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| 15 | #include <errno.h>
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| 16 | #include <unistd.h>
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| 17 | #include <dirent.h>
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| 18 | #include <limits.h>
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| 19 | #include <string.h>
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| 20 |
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| 21 | static int addpath(const char *path, char **ap, const char *entry)
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| 22 | /* Add the name of a directory entry at the front of the path being built.
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| 23 | * Note that the result always starts with a slash.
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| 24 | */
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| 25 | {
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| 26 | const char *e= entry;
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| 27 | char *p= *ap;
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| 28 |
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| 29 | while (*e != 0) e++;
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| 30 |
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| 31 | while (e > entry && p > path) *--p = *--e;
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| 32 |
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| 33 | if (p == path) return -1;
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| 34 | *--p = '/';
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| 35 | *ap= p;
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| 36 | return 0;
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| 37 | }
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| 38 |
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| 39 | static int recover(char *p)
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| 40 | /* Undo all those chdir("..")'s that have been recorded by addpath. This
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| 41 | * has to be done entry by entry, because the whole pathname may be too long.
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| 42 | */
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| 43 | {
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| 44 | int e= errno, slash;
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| 45 | char *p0;
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| 46 |
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| 47 | while (*p != 0) {
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| 48 | p0= ++p;
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| 49 |
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| 50 | do p++; while (*p != 0 && *p != '/');
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| 51 | slash= *p; *p= 0;
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| 52 |
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| 53 | if (chdir(p0) < 0) return -1;
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| 54 | *p= slash;
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| 55 | }
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| 56 | errno= e;
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| 57 | return 0;
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| 58 | }
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| 59 |
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| 60 | char *getcwd(char *path, size_t size)
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| 61 | {
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| 62 | struct stat above, current, tmp;
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| 63 | struct dirent *entry;
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| 64 | DIR *d;
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| 65 | char *p, *up, *dotdot;
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| 66 | int cycle;
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| 67 |
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| 68 | if (path == nil || size <= 1) { errno= EINVAL; return nil; }
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| 69 |
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| 70 | p= path + size;
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| 71 | *--p = 0;
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| 72 |
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| 73 | if (stat(".", ¤t) < 0) return nil;
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| 74 |
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| 75 | while (1) {
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| 76 | dotdot= "..";
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| 77 | if (stat(dotdot, &above) < 0) { recover(p); return nil; }
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| 78 |
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| 79 | if (above.st_dev == current.st_dev
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| 80 | && above.st_ino == current.st_ino)
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| 81 | break; /* Root dir found */
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| 82 |
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| 83 | if ((d= opendir(dotdot)) == nil) { recover(p); return nil; }
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| 84 |
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| 85 | /* Cycle is 0 for a simple inode nr search, or 1 for a search
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| 86 | * for inode *and* device nr.
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| 87 | */
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| 88 | cycle= above.st_dev == current.st_dev ? 0 : 1;
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| 89 |
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| 90 | do {
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| 91 | char name[3 + NAME_MAX + 1];
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| 92 |
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| 93 | tmp.st_ino= 0;
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| 94 | if ((entry= readdir(d)) == nil) {
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| 95 | switch (++cycle) {
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| 96 | case 1:
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| 97 | rewinddir(d);
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| 98 | continue;
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| 99 | case 2:
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| 100 | closedir(d);
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| 101 | errno= ENOENT;
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| 102 | recover(p);
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| 103 | return nil;
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| 104 | }
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| 105 | }
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| 106 | if (strcmp(entry->d_name, ".") == 0) continue;
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| 107 | if (strcmp(entry->d_name, "..") == 0) continue;
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| 108 |
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| 109 | switch (cycle) {
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| 110 | case 0:
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| 111 | /* Simple test on inode nr. */
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| 112 | if (entry->d_ino != current.st_ino) continue;
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| 113 | /*FALL THROUGH*/
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| 114 |
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| 115 | case 1:
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| 116 | /* Current is mounted. */
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| 117 | strcpy(name, "../");
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| 118 | strcpy(name+3, entry->d_name);
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| 119 | if (stat(name, &tmp) < 0) continue;
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| 120 | break;
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| 121 | }
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| 122 | } while (tmp.st_ino != current.st_ino
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| 123 | || tmp.st_dev != current.st_dev);
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| 124 |
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| 125 | up= p;
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| 126 | if (addpath(path, &up, entry->d_name) < 0) {
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| 127 | closedir(d);
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| 128 | errno = ERANGE;
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| 129 | recover(p);
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| 130 | return nil;
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| 131 | }
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| 132 | closedir(d);
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| 133 |
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| 134 | if (chdir(dotdot) < 0) { recover(p); return nil; }
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| 135 | p= up;
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| 136 |
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| 137 | current= above;
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| 138 | }
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| 139 | if (recover(p) < 0) return nil; /* Undo all those chdir("..")'s. */
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| 140 | if (*p == 0) *--p = '/'; /* Cwd is "/" if nothing added */
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| 141 | if (p > path) strcpy(path, p); /* Move string to start of path. */
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| 142 | return path;
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| 143 | }
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