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
5
votes
1 answer
How to make sense of O_RDONLY = 0?
I am dealing with file status flags.
Among test I performed, I found
#include
#include "fcntl.h"
int main() {
const int flag = O_RDONLY;
printf( "*** Flag O_RDONLY = %5d\n", flag);
return 0;
}
produces this output
*** Flag…
sancho.s ReinstateMonicaCellio
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5
votes
2 answers
Where is flock() for Perl on Windows?
I have a Perl script that I'd like to run on Windows, using either Strawberry Perl or ActivePerl; I don't care which. This script however, uses flock() calls, which does not seem to be included in either of those versions of Perl.
Can anyone help…
gbjbaanb
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5
votes
1 answer
Can I get fcntl and Perl alarms to cooperate?
I'm on linux, nfs, with multiple machines involved.
I'm trying to use fcntl to implement filelocking. I was using flock until I discovered it only works between processes on the same machine.
Now when I call fcntl with F_SETLKW, perl alarms (for…
mmccoo
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5
votes
2 answers
Is a Java FileLock a POSIX advisory (fcntl) lock
I have a C++ program that locks files using POSIX advisory locks. That is, it uses the POSIX fcntl system call for lock operations. I want a Java program to interoperate with that C++ program, so I want my Java program to also use POSIX advisory…
Raedwald
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5
votes
1 answer
Are POSIX file locks reentrant?
I am using POSIX mandatory file locks through fcntl. I'm wondering if those locks are reentrant, ie. can a process acquire a lock it already owns ?
paradigmatic
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4
votes
2 answers
What is the order in which a POSIX system clears the file locks that were not unlocked cleanly?
The POSIX specification for fcntl() states:
All locks associated with a file for a given process shall be removed when a file descriptor for that file is closed by that process or the process holding that file descriptor terminates.
Is this…
Daniel Trebbien
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4
votes
2 answers
How to get the mode of a file descriptor?
I mean to use fdopen
FILE *fdopen(int fd, const char *mode);
In man pages, it is stated that "The mode of the stream (one of the values "r", "r+", "w", "w+", "a", "a+") must be compatible with the mode of the file descriptor."
So I have to first…
sancho.s ReinstateMonicaCellio
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4
votes
0 answers
How to create symbolic link to a path that contains unicode characters?
I am using UNIX function symlink() to link a path that contains Unicode characters. However, when I read the link, it is returning ? instead of Unicode characters.
This is what my method looks like :
if (symlink("symlink.jpg", "/real/path/光芒.jpg")…
blackbeard
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4
votes
2 answers
What is the compelling use case for the FD_CLOEXEC flag?
I've just read this:
What does the FD_CLOEXEC fcntl() flag do?
and I understand what FD_CLOEXEC does, but not why it's important. Why not just close all the relevant file descriptors before exec()ing something? And why is it so critical to set…
einpoklum
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4
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1 answer
Why is File::FcntlLock's l_type always "F_UNLCK" even if the file is locked?
The Perl subroutine below uses File::FcntlLock to check if a file is locked.
Why does it return 0 and print /tmp/test.pid is unlocked. even if the file is locked?
sub getPidOwningLock {
my $filename = shift;
my $fs = new File::FcntlLock;
…
Saulo Silva
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4
votes
1 answer
Disable DSUSP in Python
An OSX user submitted a bug that CTRL+Y causes a python terminal application to be suspended, via dsusp causing SIGTSTP to be sent when the Python program tried to read on stdin. The code below to solves the problem: (context)
import sys
import…
Thomas
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4
votes
3 answers
when is the arg for F_GETFL fcntl command required?
int fcntl(int fd, int command, ... /* arg */ );
Is it portable: flags = fcntl(fd, F_GETFL); (note: no arg)?
Both Linux and FreeBSD man pages say that arg is ignored:
F_GETFL (void)
Get the file access mode and the file status flags; arg
is…
jfs
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4
votes
1 answer
USB Stick Serial number in Python
I am trying to get the serial number (or any unique hardware based identifier) of a USB flash drive using Python on Linux. I started with the recipe I found in this SO question.
The code in that link work great for fixed hard drives. For example…
meawoppl
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4
votes
3 answers
fcntl() for thread or process synchronization?
Is it possible to use fcntl() system call on a file to achieve thread/process synchronization (instead of semaphoress)?
raj_arni
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4
votes
2 answers
how to use O_ASYNC and fcntl in perl?
i want to use O_ASYNC option and when the pipe can read ,
the SIGIO's handler will run .
but the following code are not work . any one can help me ?
#!/bin/env perl
use Fcntl;
$SIG{IO}= sub {
print "catch SIGIO!\n";
};
my…
Chinaxing
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