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1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * xreadlink.c - safe implementation of readlink.
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4 | * Returns a NULL on failure...
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5 | */
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6 |
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7 | #include "libbb.h"
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8 |
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9 | /*
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10 | * NOTE: This function returns a malloced char* that you will have to free
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11 | * yourself. You have been warned.
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12 | */
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13 | char *xmalloc_readlink(const char *path)
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14 | {
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15 | enum { GROWBY = 80 }; /* how large we will grow strings by */
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16 |
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17 | char *buf = NULL;
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18 | int bufsize = 0, readsize = 0;
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19 |
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20 | do {
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21 | buf = xrealloc(buf, bufsize += GROWBY);
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22 | readsize = readlink(path, buf, bufsize);
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23 | if (readsize == -1) {
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24 | free(buf);
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25 | return NULL;
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26 | }
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27 | } while (bufsize < readsize + 1);
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28 |
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29 | buf[readsize] = '\0';
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30 |
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31 | return buf;
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32 | }
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33 |
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34 | char *xmalloc_readlink_or_warn(const char *path)
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35 | {
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36 | char *buf = xmalloc_readlink(path);
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37 | if (!buf) {
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38 | /* EINVAL => "file: Invalid argument" => puzzled user */
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39 | bb_error_msg("%s: cannot read link (not a symlink?)", path);
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40 | }
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41 | return buf;
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42 | }
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43 |
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44 | /* UNUSED */
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45 | #if 0
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46 | char *xmalloc_realpath(const char *path)
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47 | {
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48 | #if defined(__GLIBC__) && !defined(__UCLIBC__)
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49 | /* glibc provides a non-standard extension */
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50 | return realpath(path, NULL);
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51 | #else
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52 | char buf[PATH_MAX+1];
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53 |
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54 | /* on error returns NULL (xstrdup(NULL) ==NULL) */
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55 | return xstrdup(realpath(path, buf));
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56 | #endif
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57 | }
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58 | #endif
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