vshost-util-vserver

Build script and sources for util-vserver.
git clone https://ccx.te2000.cz/git/vshost-util-vserver
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lockfile.c (4059B)

      1 // $Id$    --*- c -*--
      2 
      3 // Copyright (C) 2004 Enrico Scholz <enrico.scholz@informatik.tu-chemnitz.de>
      4 //  
      5 // This program is free software; you can redistribute it and/or modify
      6 // it under the terms of the GNU General Public License as published by
      7 // the Free Software Foundation; version 2 of the License.
      8 //  
      9 // This program is distributed in the hope that it will be useful,
     10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
     11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     12 // GNU General Public License for more details.
     13 //  
     14 // You should have received a copy of the GNU General Public License
     15 // along with this program; if not, write to the Free Software
     16 // Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
     17 
     18 
     19 #ifdef HAVE_CONFIG_H
     20 #  include <config.h>
     21 #endif
     22 
     23 #include "util.h"
     24 
     25 #include <unistd.h>
     26 #include <errno.h>
     27 #include <string.h>
     28 #include <fcntl.h>
     29 #include <signal.h>
     30 #include <stdio.h>
     31 #include <time.h>
     32 #include <sys/file.h>
     33 #include <sys/param.h>
     34 
     35 static void
     36 showHelp(char const *cmd)
     37 {
     38   WRITE_MSG(1, "Usage:  ");
     39   WRITE_STR(1, cmd);
     40   WRITE_MSG(1,
     41 	    " [--] <lockfile> <syncpipe> [<timeout>]\n\n"
     42 	    "Protocol:\n"
     43 	    "  1.  parent (shell) creates a named <syncpipe>\n"
     44 	    "  2.  'lockfile' will be called\n"
     45 	    "  3a. 'lockfile' waits until somebody opens the <syncpipe> for reading\n"
     46 	    "  3b. parent (shell) opens the pipe for reading and blocks\n"
     47 	    "  4.  'lockfile' calls lockf() on the <lockfile>\n"
     48 	    "  5.  'lockfile' closes the <syncpipe>\n"
     49 	    "  6.  parent (shell) unlocks since <syncpipe> is closed\n"
     50 	    "  7.  'lockfile' goes into infinite loop\n"
     51 	    "  8.  parent sends SIGHUP (or other signal) to 'lockfile\n"
     52 	    "\n"
     53 	    "Sample code:\n"
     54 	    "  tmp=$(mktemp /tmp/lock.XXXXXX)\n"
     55 	    "  rm -f $tmp    # safe since mknod(2) does not follow symlinks\n"
     56 	    "  mkfifo -m700 $tmp || exit 1\n"
     57 	    "  lockfile $lock $tmp &\n"
     58 	    "  $tmp\n"
     59 	    "  ... <actions> ...\n"
     60 	    "  kill -HUP $!  # (implicated by shell-exit)\n"
     61 	    "\n"
     62 	    "Please report bugs to " PACKAGE_BUGREPORT "\n");
     63   exit(0);
     64 }
     65 
     66 static void
     67 showVersion()
     68 {
     69   WRITE_MSG(1,
     70 	    "lockfile " VERSION " -- locks a file"
     71 	    "This program is part of " PACKAGE_STRING "\n\n"
     72 	    "Copyright (C) 2004 Enrico Scholz\n"
     73 	    VERSION_COPYRIGHT_DISCLAIMER);
     74   exit(0);
     75 }
     76 
     77 static void
     78 alarmFunc(int UNUSED sig)
     79 {
     80   signal(SIGALRM, alarmFunc);
     81 }
     82 
     83 static void
     84 quitFunc(int UNUSED sig)
     85 {
     86   _exit(0);
     87 }
     88 
     89 int main(int argc, char *argv[])
     90 {
     91   int			fd, sync_fd = -1;
     92   int			idx = 1;
     93   time_t		end_time;
     94   pid_t const		ppid = getppid();
     95 
     96   if (argc>=2) {
     97     if (strcmp(argv[1], "--help")   ==0) showHelp(argv[0]);
     98     if (strcmp(argv[1], "--version")==0) showVersion();
     99     if (strcmp(argv[1], "--")       ==0) ++idx;
    100   }
    101 
    102   if (argc<idx+2) {
    103     WRITE_MSG(2, "Not enough parameters; use '--help' for more information\n");
    104     return EXIT_FAILURE;
    105   }
    106 
    107   end_time = time(0);
    108   if (argc==idx+3) end_time += atoi(argv[idx+2]);
    109   else             end_time += 300;
    110 		   
    111   if ((sync_fd=open(argv[idx+1], O_WRONLY))==-1)
    112     perror("lockfile: open(<syncpipe>)");
    113   else if ((fd=open(argv[idx], O_CREAT|O_WRONLY|O_NOFOLLOW|O_NONBLOCK, 0644))==-1)
    114     perror("lockfile: open(<lockfile>)");
    115   else if (unlink(argv[idx+1])==-1)
    116     perror("lockfile: unlink(<syncpipe>)");
    117   else if (siginterrupt(SIGALRM, 1)==-1)
    118     perror("lockfile: siginterrupt()");
    119   else if (signal(SIGALRM, alarmFunc)==SIG_ERR ||
    120 	   signal(SIGHUP,  quitFunc) ==SIG_ERR)
    121     perror("lockfile: signal()");
    122   else while (time(0)<end_time && getppid()==ppid) {
    123     int		duration = end_time-time(0);
    124     alarm(MIN(10, MAX(duration,1)));
    125 
    126     if (lockf(fd,F_LOCK,0)==-1) {
    127       if (errno==EINTR) continue;
    128       perror("lockfile: lockf()");
    129       break;
    130     }
    131     signal(SIGALRM, SIG_IGN);
    132 
    133     WRITE_MSG(sync_fd, "#!/bin/true\n");
    134     close(sync_fd);
    135     while (getppid()==ppid) sleep(10);
    136 	   
    137     return EXIT_SUCCESS;
    138   }
    139 
    140   if (sync_fd!=-1)
    141     WRITE_MSG(sync_fd, "#!/bin/false\n");
    142   return EXIT_FAILURE;
    143 }