Tag: flock

using file lock for a single instance program fails if spawn child process

I need to have a single instance program in Linux. That is if someone tries to run the program the new instance should print a message and exit. At the moment I have a lock mechanism like this: The problem is if I do anything that spawns child processes using int system(const char *command); and at some point, someone uses

Unable to lock file linux

file flock linux

I’m trying to lock a file and obviously there is something I’m missing, because eventhough it seems it’s locked I can still access and edit it using vim editor. Locking file: Checking using lslocks: But still able to access it and edit using different terminal (different process I believe). I tried the solution with file descriptors here Linux flock, how

Same program/process acquiring lock every time when using LOCK_NB with LOCK_EX flag

c++ flock linux python

I have a requirement, where two separate processes/programs running in parallel (One written in Python and one written in C++) need to get exclusive access, modifying a hardware related value. I’m trying to attain synchronization between them using flock. The code for the same is as below, Python Code C++ Code But, when I run these two programs in parallel,

Why does flock removes existing text from a file?

bash flock linux shell

So, I am trying to get an exclusive lock on a text file using Flock and a line of text to that file however while doing so it removes whatever text was there earlier. So if the file had let’s say and after running the script I am expecting something like instead, all I get is why would it behave

flock: -c requires exactly one command argument

cron flock linux php

We have multiple cronjobs running on our system. The problem is that we run them every hour, and therefore sometimes the cronjob didn’t finish and a new instance has started. Because of that, we wanted to use flock so the script only gets executed once. However, when I have this in my crontab or run it alone I’m getting the

How do I use the linux flock command to prevent another root process from deleting a file?

bash file-locking flock linux

I would like to prevent one of my root processes from deleting a certain file. So I came across the flock command, it seems to fit my need, but I didn’t get its syntax. If I only indicate a shared lock, it doesn’t work: If I add a timeout parameter, it still doesn’t work: It seems that way, it fits