lockf.c 2.2 KB

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  1. /* Copyright (C) 1994, 1996, 1997, 1998, 2000 Free Software Foundation, Inc.
  2. This file is part of the GNU C Library.
  3. The GNU C Library is free software; you can redistribute it and/or
  4. modify it under the terms of the GNU Library General Public License as
  5. published by the Free Software Foundation; either version 2 of the
  6. License, or (at your option) any later version.
  7. The GNU C Library is distributed in the hope that it will be useful,
  8. but WITHOUT ANY WARRANTY; without even the implied warranty of
  9. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  10. Library General Public License for more details.
  11. You should have received a copy of the GNU Library General Public
  12. License along with the GNU C Library; see the file COPYING.LIB. If not,
  13. write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  14. Boston, MA 02111-1307, USA. */
  15. #include <features.h>
  16. #include <sys/types.h>
  17. #include <unistd.h>
  18. #include <fcntl.h>
  19. #include <errno.h>
  20. #include <string.h>
  21. /* libc_hidden_proto(lockf) */
  22. /* Experimentally off - libc_hidden_proto(memset) */
  23. /* libc_hidden_proto(fcntl) */
  24. /* libc_hidden_proto(getpid) */
  25. /* lockf is a simplified interface to fcntl's locking facilities. */
  26. int lockf (int fd, int cmd, off_t len)
  27. {
  28. struct flock fl;
  29. memset ((char *) &fl, '\0', sizeof (fl));
  30. /* lockf is always relative to the current file position. */
  31. fl.l_whence = SEEK_CUR;
  32. fl.l_start = 0;
  33. fl.l_len = len;
  34. switch (cmd)
  35. {
  36. case F_TEST:
  37. /* Test the lock: return 0 if FD is unlocked or locked by this process;
  38. return -1, set errno to EACCES, if another process holds the lock. */
  39. fl.l_type = F_RDLCK;
  40. if (fcntl (fd, F_GETLK, &fl) < 0)
  41. return -1;
  42. if (fl.l_type == F_UNLCK || fl.l_pid == getpid ())
  43. return 0;
  44. __set_errno(EACCES);
  45. return -1;
  46. case F_ULOCK:
  47. fl.l_type = F_UNLCK;
  48. cmd = F_SETLK;
  49. break;
  50. case F_LOCK:
  51. fl.l_type = F_WRLCK;
  52. cmd = F_SETLKW;
  53. break;
  54. case F_TLOCK:
  55. fl.l_type = F_WRLCK;
  56. cmd = F_SETLK;
  57. break;
  58. default:
  59. __set_errno(EINVAL);
  60. return -1;
  61. }
  62. return fcntl(fd, cmd, &fl);
  63. }
  64. libc_hidden_def(lockf)