/* Copyright (C) 1994, 1996, 1997, 1998, 2000 Free Software Foundation, Inc. This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Library General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. The GNU C Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public License for more details. You should have received a copy of the GNU Library General Public License along with the GNU C Library; see the file COPYING.LIB. If not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #include <sys/types.h> #include <unistd.h> #include <fcntl.h> #include <errno.h> #include <string.h> /* lockf is a simplified interface to fcntl's locking facilities. */ int lockf (int fd, int cmd, off_t len) { struct flock fl; memset ((char *) &fl, '\0', sizeof (fl)); /* lockf is always relative to the current file position. */ fl.l_whence = SEEK_CUR; fl.l_start = 0; fl.l_len = len; switch (cmd) { case F_TEST: /* Test the lock: return 0 if FD is unlocked or locked by this process; return -1, set errno to EACCES, if another process holds the lock. */ fl.l_type = F_RDLCK; if (fcntl (fd, F_GETLK, &fl) < 0) return -1; if (fl.l_type == F_UNLCK || fl.l_pid == getpid ()) return 0; __set_errno(EACCES); return -1; case F_ULOCK: fl.l_type = F_UNLCK; cmd = F_SETLK; break; case F_LOCK: fl.l_type = F_WRLCK; cmd = F_SETLKW; break; case F_TLOCK: fl.l_type = F_WRLCK; cmd = F_SETLK; break; default: __set_errno(EINVAL); return -1; } return fcntl(fd, cmd, &fl); }