file - python fcntl does not lock as expected (2) -

-

i'd use lock_ex prevent other processes modify file under modification.

process a:

from fcntl import flock, lock_ex, lock_nb time import sleep f=open("tmp.txt", "w") flock(f.fileno(), lock_ex|lock_nb) f.write("xxxx") f.flush() sleep(20) f.close()

5 seconds after starts, process b:

f=open("tmp.txt", "w") f.close()

and "tmp.txt" emptied process b... no ioerror raised in process b. how can 1 prevent "tmp.txt" modified 2 processes using exclusive access ?

note: "innocent" process b not use flock(), fopen() create new file. what's use of exclusive lock on file if else can modify file ? of course, if b uses flock() well, raises ioerror, if not ???

by default, flock advisory locking mechanism. more details, see this question.


Comments

Post a Comment

Popular posts from this blog

c++ - Creating new partition disk winapi -

-
i'am trying create new partition , mount volume new, thought createfile let me this, code : lpctstr lpfilename=l"\\\\.\\device\\harddisk0\\partition3"; handle handl=createfile( lpfilename, generic_read | generic_write, file_share_read | file_share_write, null, create_always, file_attribute_normal, null ); if (handl==invalid_handle_value) { qdebug()<<"handl invalid"<<" error"<<getlasterror();} bool success = definedosdevice(ddd_raw_target_path,l"i:",l"\\device\\harddisk0\\partition3"); if(!success) qdebug()<<" definedosdevice failed "<<getlasterror(); bflag = getvolumenameforvolumemountpoint( l"i:\\", // input volume mount point or directory /** u in dir
Read more

Android Prevent Bluetooth Pairing Dialog -

-
i'm developing internal application uses bluetooth printing. want bluetooth pairing occur without user input. have managed working trapping android.bluetooth.device.action.pairing_request broadcast. in broadcast receiver call setpin method, , pairing works ok, bluetoothpairingdialog displayed second or two, disappears - see link below. https://github.com/android/platform_packages_apps_settings/blob/master/src/com/android/settings/bluetooth/bluetoothpairingdialog.java since broadcast non-ordered, can't call abortbroadcast() , , wondering if there other way prevent pairing dialog appearing. can hook window manager in way? i haven't been able come way without modifying sdk. if you're oem, it's easy (i'm on 4.3): in packages/apps/settings/androidmanifest.xml, comment intent filter pairing dialog: <activity android:name=".bluetooth.bluetoothpairingdialog" android:label="@string/bluetooth_pairing_request"
Read more

VBA function to include CDATA -

-
i have following function include cdata: function cdatasection() dim objdom domdocument dim objkmlrootelement ikmldomelement dim objkmlelement ikmldomelement dim cdata ikmldomcdatasection set objdom = new domdocument set objkmlrootelement = objdom.createelement("balloonstyle") objdom.appendchild objkmlrootelement set objkmlelement = objdom.createelement("text") objkmlrootelement.appendchild objkmlelement set cdata = objdom.createcdatasection("text") cdata.data = "<![cdata[<b>latitude = $[latitude]</b>?]]>;" end function when run above, getting error "user defined data type not found" function. yes ripster says find library reference. vba window tools>references for list of relevant references see... http://msdn.microsoft.com/en-us/library/windows/desktop/ms763701%28v=vs.85%29.aspx however, if have hard time tracking down reference, replace dim sta
Read more