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

basic authentication with http post params android -

i doing basic authentication passing username , password , using basicnamevaluepair sending post params response service. my method: public stringbuilder callservicehttppost(string username, string password, string type) { // create new httpclient , post header httpclient httpclient = new defaulthttpclient(); httppost httppost = new httppost(webservice + type); httpresponse response = null; stringbuilder total = new stringbuilder(); try { url url = new url(webservice + type); /*string base64encodedcredentials = base64.encodetostring((username + ":" + password).getbytes(), base64.url_safe | base64.no_wrap);*/ string base64encodedcredentials = "basic " + base64.encodetostring( (username + ":" + password).getbytes(), base64.no_wrap); httppost.setheader("auth...
Read more

vb.net - Virtual Keyboard commands -

i wondering difference between virtual these keyboard commands is: keyeventf_extendedkey , keyeventf_keyup is. everywhere have looked gives me description based off integers , not want know each of them does. you've tagged question vb.net, these have nothing @ vb.net. they're constants defined in windows header files, use win32 api functions. as far difference, can't tell looking @ values. individual values not particularly important, that's why named identifiers used. what's important used , documentation functions tells mean. the first one, keyeventf_extendedkey , used keybdinput structure (which used along e.g. sendinput function) pass information synthesized keyboard input. if flag used, means scan code should interpreted extended key. technically, means scan code preceded prefix byte value 224 (&he0 in hexadecimal notation). the second one, keyeventf_keyup , 1 of flags available use structure. means key being released (going up)...
Read more

css - Firefox for ubuntu renders wrong colors -

Image
i've got following problem: i'm developing website, while testing around i've noticed firefox , chromium display css bar in different colors. when switched between several machine come conclusion firefox ubuntu problem. on other devices i've tested website. it's fine. the differences between chrome , firefox rendering: firefox: chromium: note: firefox ubuntu problem. does knows why , came solution? https://bugzilla.mozilla.org/show_bug.cgi?id=655637 bug 629312 - firefox displays wrong colors on image (only linux) open about:config , rechange gfx.color_management.mode 2 0.
Read more