I am using a Linux periodic timer, in particular, timerfd, which I set to expire periodically, for instance, every 200 ms. I noticed, however, that the timer seems to expire, sometimes, a little before with respect to the timeout I set. In particular, I’m using the following C code to perform a simple t…
Tag: linux
top and grep output nothing when run from shell script
I am trying to create shell script that ssh into a remote server and run a script there and print the output in the local server but when I run the script in the local server it most of the time outputs nothing and rarely outputs data : and when I ssh in the local server to the remote server
blocking all internal traffic except incoming traffic from a specific ip on a single port
I’m trying to use IPtables to block all internal traffic with the exception of one server, here are my rules but when i telnet from another instance i can still connect…. Answer When debugging iptables I normally: reset all the counter – ‘iptables -Z’ make the connection then rev…
Unable to get the absolute value of command output
So I wanted to make a simple script to keep checking the CPU temperature of my RasPi, which is stored in /sys/class/thermal/thermal_zone0/temp , and hence cat /sys/class/thermal/thermal_zone0/temp would give the temp, but like this : which essentially means 38.459 degree Celsius. I was unable to format the ou…
conditionally merge files by appending in bash
I have two files and would like to merge them – by appending to the last line. file1.txt content file2.txt content Desired outcome – file3.txt How do I go about this, please? Note, zero is in place for null in the Stack line. Answer Using awk: When file2.txt is read, store field2 in array a using …
How can I time out an input/output redirection in Linux?
I was wondering whether or not it is possible to time out an input/output redirection in Linux. Meaning that I would like to redirect certain input/output to a file just for a time span of 2s for instance. In a practical case, I am looking to cat the tty0 to a file only during 2s How can I achieve this?
How do I add a numbered suffix at the end of my files using split on Linux BASH?
I’m using the split command in a Macbook and instead of getting numbers, I’m getting files such as output_aa, output_ab, output_ac, and what I need is output_1 , output_2, output_3, and so on. Here’s the code I’m using, it’s on a .txt of a book (Harry Potter) and I’m trying…
Shell : create and assign variables inside for loop
i ve this shell script ; it’s a loop which set in the variable “a” each time result : My Purpose is how to change “a” by a dynamic variable name which be $item_MYPREFIX (concatination :$item + _MYPREFIX ) So that my code would be generic , something like this : and i would be abl…
Why does SIGHUP not work on busybox sh in an Alpine Docker container?
Sending SIGHUP with to a busybox sh process on my native system works as expected and the shell hangs up. However, if I use docker kill to send the signal to a container with it doesn’t do anything. The Alpine container is still running: By the way, with an Ubuntu container (which runs bash) it does wor…
Immutable names in /dev/disk
There are four entries in /dev/disk which I am interested in. by-id by-label by-path by-uuid Which of the entries contain immutable names for physical drives? By immutable, I mean that the name shouldn’t change if I change the usb/pci port used to connect to the drive. destroy and create partitions (GPT…