Attachment 161405 Details for Bug 252000 – Get a shared lock then attempt to promote to an exclusive lock

Get a shared lock then attempt to promote to an exclusive lock

flock_SH_EX.c (text/x-csrc), 1.33 KB, created by Matt Brookover on 2007-08-15 21:24:41 UTC

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Creator: Matt Brookover

Created: 2007-08-15 21:24:41 UTC

Size: 1.33 KB

patch

obsolete

>#include <stdio.h>
>#include <unistd.h>
>#include <sys/types.h>
>#include <sys/stat.h>
>#include <fcntl.h>
>#include <sys/file.h>
>#include <string.h>
>#include <time.h>
>#include <errno.h>
>
>int readlock(char *filename)
>{
>	int fd;
>
>	if ((fd=open(filename,O_CREAT|O_RDWR,S_IRUSR|S_IWUSR|S_IRGRP))==-1)
>	{
>		fprintf (stderr,"Could not open %s:",filename);
>		perror ("");
>		exit(1);
>	}
>
>	while (flock(fd,LOCK_SH) == -1)
>	{
>		if (errno!=EAGAIN)
>		{
>			fprintf (stderr,"Could not get shared lock on %s errno=%s:",filename,strerror(errno));
>			exit(1);
>		}
>		printf ("%s locked, trying again to get shared lock\n",filename);
>		sleep (2);
>	}
>
>	printf ("Have shared lock, hit return to promote shared lock to exclusive lock on %s\n",filename);
>	fgetc(stdin);
>	printf ("Waiting to get exclusive lock\n");
>	while (flock(fd,LOCK_EX) == -1)
>	{
>		if (errno!=EAGAIN)
>		{
>			fprintf (stderr,"Could not get exclusive lock on %s errno=%s\n",filename,strerror(errno));
>			exit(1);
>		}
>		printf ("%s locked, trying again to get exclusive lock\n",filename);
>		sleep (2);
>	}
>
>	printf ("Have exclusive lock, hit return to free exclusive lock on %s and exit\n",filename);
>	fgetc(stdin);
>
>	if (flock(fd,LOCK_UN) == -1)
>	{
>		fprintf (stderr,"Could unlock %s:",filename);
>		perror ("");
>		exit(1);
>	}
>
>	close(fd);
>}
>
>main(int argc, char *argv[])
>{
>	int fd;
>	int i;
>	fd=readlock(argv[1]);
>}
>

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Attachments on bug 252000: 161204 | 161205 | 161405 | 161406