flock.c 1.7 KB

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  1. /* Copyright (C) 1992, 1995, 1996, 1997 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. /* This file implements the `flock' function in terms of the POSIX.1 `fcntl'
  16. locking mechanism. In 4BSD, these are two incompatible locking mechanisms,
  17. perhaps with different semantics? */
  18. #include <errno.h>
  19. #include <unistd.h>
  20. #include <fcntl.h>
  21. #include <sys/file.h>
  22. /* Apply or remove an advisory lock, according to OPERATION,
  23. on the file FD refers to. */
  24. int flock( int fd, int operation)
  25. {
  26. struct flock lbuf;
  27. switch (operation & ~LOCK_NB) {
  28. case LOCK_SH:
  29. lbuf.l_type = F_RDLCK;
  30. break;
  31. case LOCK_EX:
  32. lbuf.l_type = F_WRLCK;
  33. break;
  34. case LOCK_UN:
  35. lbuf.l_type = F_UNLCK;
  36. break;
  37. default:
  38. __set_errno(EINVAL);
  39. return -1;
  40. }
  41. lbuf.l_whence = SEEK_SET;
  42. lbuf.l_start = lbuf.l_len = 0L; /* Lock the whole file. */
  43. return fcntl(fd, (operation & LOCK_NB) ? F_SETLK : F_SETLKW, &lbuf);
  44. }