de.weAut.demos

Class JustNotFLock

java.lang.Object

de.weAut.demos.JustNotFLock

All Implemented Interfaces:

ComVar, PiUtil, PiVals

public class JustNotFLock
extends Object
implements PiUtil

Demo (Test) of incompatible Java and C file lock.

This program tries to acquire a standard nio lock on the file optionally given by first argument or on /home/pi/bin/.lockPiGpio. On success it holds this lock for 1 min 20s or until being interrupted or killed.

Run by:

    java  de.weAut.demos.JustNotFLock [filePath]
    default filePath] is PiUtil.lckPiGpioPth or
    PiUtil.lckWinGpioPth (on Windows)

On a Raspberry with a Raspian lite (Linux) this program may demonstrate that it won't respect a lock on the same file by the little C program JustLock e.g. — and vice versa. The reason is the Java'a FileLock not using the operating system's first (historic standard) file lock mechanism.
See the post.

The repair is to use PiUtil.openLock(String, boolean) and PiUtil.closeLock() instead of overriding them here.

Copyright © 2019 Albrecht Weinert

Version:

52 (12.06.2021)

Author:

Albrecht Weinert a-weinert.de

Nested Class Summary

Nested classes/interfaces inherited from interface de.weAut.PiUtil

PiUtil.Impl, PiUtil.LeTick

Field Summary

Fields inherited from interface de.weAut.PiUtil

ERR_ASSIGN_PIN, ERR_CLOSE_WDOG, ERR_NoGPIOLOCK, ERR_NoLOCKFILE, ERR_NoLOCKPROC, ERR_NOT_LOCKED, ERR_OPEN_W_DOG, ERR_PIGPIOD_CON, lckPiGpioPth, lckWinGpioPth

Fields inherited from interface de.weAut.PiVals

GPIO_INP, GPIO_OUT, GPIOmax, GPIOmin, GPIOutM, H1, HI, L0, LO, PI_PUD_DOWN, PI_PUD_DT, PI_PUD_KP, PI_PUD_OFF, PI_PUD_UP, PIN0, PIN00, PIN01, PIN02, PIN04, PIN06, PIN09, PIN0V, PIN1, PIN14, PIN17, PIN2, PIN20, PIN25, PIN3V, PIN4, PIN5V, PIN6, PIN9, PINig, PINix, PIO_ALT0, PIO_ALT1, PIO_ALT2, PIO_ALT3, PIO_ALT4, PIO_ALT5

Fields inherited from interface de.frame4j.util.ComVar

AUTHOR, BLANK_STRING, cons, CONSOL_ENCODING, COPYRIGHT, D, D_NaN, D_NegInf, D_PosInf, EMPTY_INT_A, EMPTY_STRING, FILE_ENCODING, FRW_CLLD, FS, FSS, H, hasCons, HOST_IP, HOST_IPv4, HOST_NAME, INIT_ERROR, JAR_ENCODING, JH, JOB_DONE_OK, JRL, LOG_OUT_ERROR, M, MAIN_THREAD_EXC, NO_BYTES, NO_CLASSES, NO_DOUBLES, NO_OBJECTS, NO_PARS_ERROR, NO_STRINGS, NOT_WINDOWS, ON_PI, ONE_DAY, ONE_HOUR, ONE_LEAP_YEAR, ONE_MINUTE, ONE_SECOND, ONE_WEEK, ONE_YEAR, OS, PROG_NAME, PROG_SHORT, PS, RUNTIME, S, SHY, UD, UL, UL_UR_da, UR

Constructor Summary

Constructors

Constructor and Description
JustNotFLock()

Method Summary

Modifier and Type	Method and Description
void	closeLock() Unlock the lock file.
void	doIt(String[] args) The application's work.
static void	main(String[] args) The application start.
int	openLock(String lckPiGpioFil, boolean verbose) Open and lock lock file.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface de.weAut.PiUtil

argHost, argPiType, argPort, argTimeout, closeWatchdog, eightDigitHex, errorText, getDelCnt, getLastExcept, getLastExcMess, getLastLockFN, getOut, getOvrCnt, getUseLock, openLockPi, openWatchdog, regAsStdMBean, repExc, setArgHost, setArgPiType, setArgPort, setArgTimeout, setUseLock, systemExit, thrDelay, triggerWatchdog, twoDigitDec

Constructor Detail

JustNotFLock

public JustNotFLock()

Method Detail

openLock

public int openLock(String lckPiGpioFil,
                    boolean verbose)

Open and lock lock file.

Specified by:

openLock in interface PiUtil

Parameters:

lckPiGpioFil - if not null or empty use this path instead of the default one (lckPiGpioPth)

verbose - true: make the lock process verbose (by option -v) on standard output

Returns:

err 0: OK; else: error, see PiUtil.ERR_NoLOCKFILE, PiUtil.ERR_NOT_LOCKED

closeLock

public void closeLock()

Unlock the lock file.

Specified by:

closeLock in interface PiUtil

main

public static void main(String[] args)

The application start.

If the first start parameter is longer than 3 characters, it will be taken as lock file path instead of /home/pi/bin/.lockPiGpio.

Can be stopped by signal (cntlC), kill command and the like.

Parameters:

args - start parameters

doIt

public void doIt(String[] args)

The application's work.