fcntl refers to a function that provides control over the open file referenced by a file descriptor
fcntl refers to a function that provides control over the open file referenced by a file descriptor.
Questions tagged [fcntl]
234 questions
3
votes
1 answer
Shared mmap co-ordination using fcntl locks?
When using mmap() for shared memory (from Linux, or other UNIX-like systems) is it possible (and portable) to use fcntl() (or flock() or lockf() functions) to co-ordinate access to the mapping?
Responses to this SO question seems to suggest that it…
Jim Dennis
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3
votes
1 answer
Why don't I see deadlock (EDEADLK) when several processes lock the same fd with F_SETLKW?
I need to properly handle EDEADLK. In my program I see that both children wait until parent sleep and, and then they apply the lock and right away they leave it. Sorry for my mistakes, I am a Spanish student.
int main(){
pid_t childpid,…
Jorge M
- 33
- 1
- 3
3
votes
0 answers
Android does not support robust futexes, so how to implement a robust mutex?
I found the pthread.h in android ndk does not include robust futexes functions, so what should I do if I want to access a shared memory(mmap) between multiple processes?
PS: Now, I use std::shared_mutex + fcntl, which the shared_mutex is for thread,…
alpha
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3
votes
3 answers
How can I read and write from files using the headers fcntl.h and unistd.h?
I'm trying to learn how to use the header files and . I have created a small example to test the workings of their procedures, but it didn't work as expected. Here is my code:
#include
#include
int main() {
…
Rontogiannis Aristofanis
- 8,883
- 8
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2
votes
3 answers
No manual entry for fcntl problem
When I use `man fcntl' got the message:
No manual entry for fcntl
which the pkg is needed to install?
ps. I use debian.
qrtt1
- 7,746
- 8
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2
votes
1 answer
How can I set a pipe to O_NONBLOCK perl
This works fine:
#!/usr/bin/perl -w
#
#pipe2 - use pipe and fork so child can send to parent
use IO::Handle;
pipe(READER, WRITER);
WRITER->autoflush(1);
if ($pid = fork) {
close WRITER;
chomp($line = );
print "Parent Pid…
user1424074
- 137
- 1
- 7
2
votes
1 answer
Docker and fcntl OSError Errno 22 Invalid argument
I've encountered a weird problem and I do not know how to proceed.
I have docker 18.09.2, build 6247962 on a VMware ESXi 6.5 virtual machine running Ubuntu 18.04. I have docker 19.03.3, build a872fc2f86 on a Azure virtual machine running Ubuntu…
Lewis M
- 550
- 3
- 7
2
votes
1 answer
Implementing lseek in xv6
First off I need to say it's completely possible I'm missing something.
My assignment is to essentially implement 'fprintf'. Now while appending to the file isn't required, I like to go above and beyond.
My issue is, I can't find a definition for…
Flacarile
- 69
- 5
2
votes
5 answers
No module named fcntl
I am trying to execute this method with IronPython on .NET 4.0 using IronPython 2.7. i am using Windows 7
import os
import re
import nltk
import urllib
import xapian
import sys
def getData(url):
try:
html = urllib.urlopen(url)
…
michelle
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- 46
2
votes
3 answers
How to tell if FILE* is referring to a directory?
I just discovered that a FILE* can not only refer to a regular file, but also to a directory. If the latter is the case, fread will fail with errno set to 21 (Is a directory).
Minimal repro can be tested here
#include
#include…
Tobi
- 2,591
- 15
- 34
2
votes
1 answer
Why can't I create read-only, shared mappings after setting F_SEAL_WRITE?
After doing fcntl(memfd, F_ADD_SEALS, F_SEAL_WRITE);, calls like mmap(NULL, 4096, PROT_READ, MAP_SHARED, memfd, 0); fail with error EPERM. Based on man 2 fcntl, my understanding of F_SEAL_WRITE is that it only prevents writable, shared mappings.…
Joseph Sible-Reinstate Monica
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2
votes
3 answers
Error with "mlflow ui" when trying to run it on MS Windows
When I run mlflow ui the following error occurred:
Traceback (most recent call last):
File "c:\anaconda3\lib\runpy.py", line 193, in _run_module_as_main
"__main__", mod_spec)
File "c:\anaconda3\lib\runpy.py", line 85, in _run_code
…
Tavakoli
- 1,303
- 3
- 18
- 36
2
votes
1 answer
Unable to read file contents into buffer using read()
Following is a sample code compiled using GNU compiler (g++ command) on an Ubuntu OS 16.04:
#include
#include
#include
#include
int main()
{ char* pBuffer;
char* storedfilepath…
vedant gala
- 428
- 3
- 18
2
votes
1 answer
fcntl F_GETLK always returns F_UNLCK
I am trying to understand POSIX file-region locks in C. The program below is really simple, sets the lock to F_WRLCK and then gets locks. There is no errors during opening/setting lock. Unfortunatelly it's always returning F_UNLCK. Where is the…
Wojtek338
- 43
- 4
2
votes
2 answers
Write magnetic tape end of record linux
Task is create two record with different sizes within one file entry.
I'm using python 3.4.5 for testing:
import fcntl
import os
import struct
MTIOCTOP = 0x40086d01 # refer to mtio.h
MTSETBLK = 20
fh = os.open('/dev/st2', os.O_WRONLY…
Pavel Voropaev
- 43
- 4