ttyname.c 3.0 KB

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  1. #include <string.h>
  2. #include <errno.h>
  3. #include <assert.h>
  4. #include <unistd.h>
  5. #include <dirent.h>
  6. #include <sys/stat.h>
  7. /* Jan 1, 2004 Manuel Novoa III
  8. *
  9. * Kept the same approach, but rewrote the code for the most part.
  10. * Fixed some minor issues plus (as I recall) one SUSv3 errno case.
  11. */
  12. /* This is a fairly slow approach. We do a linear search through some
  13. * directories looking for a match. Yes this is lame. But it should
  14. * work, should be small, and will return names that match what is on
  15. * disk. Another approach we could use would be to use the info in
  16. * /proc/self/fd, but that is even more lame since it requires /proc */
  17. /* SUSv3 mandates TTY_NAME_MAX as 9. This is obviously insufficient.
  18. * However, there is no need to waste space and support non-standard
  19. * tty names either. So we compromise and use the following buffer
  20. * length. (Erik and Manuel agreed that 32 was more than reasonable.)
  21. *
  22. * If you change this, also change _SC_TTY_NAME_MAX in libc/unistd/sysconf.c
  23. */
  24. #define TTYNAME_BUFLEN 32
  25. char *ttyname(int fd)
  26. {
  27. static char name[TTYNAME_BUFLEN];
  28. return ttyname_r(fd, name, TTYNAME_BUFLEN) ? NULL : name;
  29. }
  30. static const char dirlist[] =
  31. /* 12345670123 */
  32. "\010/dev/vc/\0" /* Try /dev/vc first (be devfs compatible) */
  33. "\011/dev/tts/\0" /* and /dev/tts next (be devfs compatible) */
  34. "\011/dev/pty/\0" /* and /dev/pty next (be devfs compatible) */
  35. "\011/dev/pts/\0" /* and try /dev/pts next */
  36. "\005/dev/\0"; /* and try walking through /dev last */
  37. int ttyname_r(int fd, char *ubuf, size_t ubuflen)
  38. {
  39. struct dirent *d;
  40. struct stat st;
  41. struct stat dst;
  42. const char *p;
  43. char *s;
  44. DIR *fp;
  45. int rv;
  46. int len;
  47. char buf[TTYNAME_BUFLEN];
  48. if (fstat(fd, &st) < 0) {
  49. return errno;
  50. }
  51. rv = ENOTTY; /* Set up the default return value. */
  52. if (!isatty(fd)) {
  53. goto DONE;
  54. }
  55. for (p = dirlist ; *p ; p += 1 + p[-1]) {
  56. len = *p++;
  57. assert(len + 2 <= TTYNAME_BUFLEN); /* dirname + 1 char + nul */
  58. strcpy(buf, p);
  59. s = buf + len;
  60. len = (TTYNAME_BUFLEN-2) - len; /* Available non-nul space. */
  61. if (!(fp = opendir(p))) {
  62. continue;
  63. }
  64. while ((d = readdir(fp)) != NULL) {
  65. /* This should never trigger for standard names, but we
  66. * check it to be safe. */
  67. if (strlen(d->d_name) > len) { /* Too big? */
  68. continue;
  69. }
  70. strcpy(s, d->d_name);
  71. if ((lstat(buf, &dst) == 0)
  72. #if 0
  73. /* Stupid filesystems like cramfs fail to guarantee that
  74. * st_ino and st_dev uniquely identify a file, contrary to
  75. * SuSv3, so we cannot be quite so precise as to require an
  76. * exact match. Settle for something less... Grumble... */
  77. && (st.st_dev == dst.st_dev) && (st.st_ino == dst.st_ino)
  78. #else
  79. && S_ISCHR(dst.st_mode) && (st.st_rdev == dst.st_rdev)
  80. #endif
  81. ) { /* Found it! */
  82. closedir(fp);
  83. /* We treat NULL buf as ERANGE rather than EINVAL. */
  84. rv = ERANGE;
  85. if (ubuf && (strlen(buf) <= ubuflen)) {
  86. strcpy(ubuf, buf);
  87. rv = 0;
  88. }
  89. goto DONE;
  90. }
  91. }
  92. closedir(fp);
  93. }
  94. DONE:
  95. __set_errno(rv);
  96. return rv;
  97. }