#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <signal.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <limits.h>
#include <getopt.h>
#include <sys/file.h>

#define failf(name) do { fprintf(stderr,"%s: ",pname); perror(name"()"); exit(EXIT_FAILURE); } while (0)
const char version[]="This is FLock, version 1.0\n";

int verbose;

char *pname;

static void usage(void) __attribute__((noreturn));
static void usage(void)
{
	fprintf(stderr,"\
%s\
This command acts as an interface to flock(2):\n\
\n\
Usage: flock [{-s|--shared}|{-x|--exclusive}] [-n|--nonblock]\n\
             [-v|--verbose] [-h|--help] [-V|--version]\n\
             <lockname> <command>\n\
\n\
  -s, --shared\tCreate shared lock (LOCK_SH) - DEFAULT\n\
  -x, --exclusive\tCreate exclusive lock (LOCK_EX)\n\
  -n, --nonblock\tFail immediately if req. lock is busy\n\
  -v, --verbose\tDisplay progress during locking\n\
  -h, --help\tPrint a summary of the options\n\
  -V, --version\tPrint the version number\n\
",version);
	exit(EXIT_FAILURE);
}

const struct option longopts[]={
{"shared"   ,0,0,'s'},
{"exclusive",0,0,'x'},
{"nonblock" ,0,0,'n'},
{"verbose"  ,0,0,'v'},
{"help"     ,0,0,'h'},
{"version"  ,0,0,'V'},
{NULL       ,0,0,0  }};

int main(int argc,char **argv)
{
char *fn,*cmd;
int locktype=LOCK_SH,nonblock=0,fd,optc;

	pname=*argv;
	while ((optc=getopt_long(argc,argv,"sxnvhV",longopts,NULL))!=EOF) switch (optc) {
		case 's':
			locktype=LOCK_SH;
			break;
		case 'x':
			locktype=LOCK_EX;
			break;
		case 'n':
			nonblock=LOCK_NB;
			break;
		case 'v':
			verbose=1;
			break;
		case 'V':
			fprintf(stderr,version);
			exit(EXIT_FAILURE);
		default: /* also 'h' */
			usage();
			break;
		}
	if (optind+2!=argc) {
		fprintf(stderr,"%s: Incorrect number of parameters (command needs quoting?)!\n",pname);
		exit(EXIT_FAILURE);
		}
	fn=argv[optind];
	cmd=argv[optind+1];
	if (verbose) { fprintf(stderr,"%s: Opening \"%s\"...",pname,fn); fflush(stderr); }
	if ((fd=open(fn,O_RDONLY|(nonblock?O_NONBLOCK:0)))==-1) failf("open");
	if (verbose) { fprintf(stderr,"done\n%s: Locking \"%s\"...",pname,fn); fflush(stderr); }
	if (flock(fd,locktype|nonblock)) failf("flock");
	if (verbose) { fprintf(stderr,"done\n%s: Running \"%s\"...",pname,cmd); fflush(stderr); }
	if (system(cmd)==-1) failf("system");
	if (verbose) { fprintf(stderr,"done\n%s: Finishing - removing lock.\n",pname); }
	return(EXIT_SUCCESS);
}