Unix and Linux Stack Exchange
Unix and Linux Stack Exchange

Questions tagged [real-time]

For questions about real-time computing and how to achieve a certain level of guaranteed response time with UNIX or Linux systems like RTLinux. For real-time clocks (RTC) use the /clock tag instead.

154 questions
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15 answers

Run unix command precisely at very short intervals WITHOUT accumulating time lag over time

Question I'd like to be able to run a UNIX command precisely every second over a long time period. I need a solution, which does not lag behind after a certain time, because of the time the command itself needs for execution. sleep, watch, and a…
porg
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16
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5 answers

Real time cmd tool to show HDD space remaining

Is there a command line tool which shows in real time how much space remains on my external hard drive?
oshirowanen
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15
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2 answers

Advantages of using a RTOS such as QNX or VxWorks instead of Linux?

When developing a solution that requires a real-time operating system, what advantages would an operating system such an QNX or VxWorks have over Linux? Or to put it another way, since these operating system are designed specifically for real-time,…
Justin Ethier
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10
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1 answer

Real time priorities in non real time OS

If I do the following command on my standard Linux Mint installation: comp ~ $ ps -eo rtprio,nice,cmd RTPRIO NI CMD ... 99 - [migration/0] 99 - [watchdog/0] 99 - [migration/1] - 0 [ksoftirqd/1] 99 - [watchdog/1] I get some of the…
TheMeaningfulEngineer
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9
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1 answer

Negatives of running processes with real-time priority?

Are there any downsides of running processes with real-time priority (chrt -f 99)? My hypothesis is that this combined with an affinity will ensure that any pre-emption of my process is minimal and therefore any jitter (specifically network latency)…
Nim
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9
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4 answers

Current time/date as a variable in BASH and stopping a program with a script

I am trying to create a raspberry pi spy cam bug. I am trying to make it so the new file created for the various processes come up with NOW=`date '+%F_%H:%M:%S'`; which works fine. but it requires an echo to update the time $NOW is also in the…
Reckless Liberty
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9
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2 answers

real time backup if file changed?

Are there any linux/unix console applications similar to Yadis that would allow me to: be set up from the console backup multiple directories backup / sync in real time after the files (text files) are changed Update 1: I write shell scripts,…
Radek
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1 answer

Why is the integer value of SIGRTMIN (first real-time signal) 34 and not 32?

Examining the output of kill -l command $ kill -l 1) SIGHUP 2) SIGINT 3) SIGQUIT 4) SIGILL 5) SIGTRAP 6) SIGABRT 7) SIGBUS 8) SIGFPE 9) SIGKILL 10) SIGUSR1 11) SIGSEGV 12) SIGUSR2 13) SIGPIPE 14) SIGALRM 15) SIGTERM 16) SIGSTKFLT 17)…
Paulo Tomé
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7
votes
1 answer

rtkit: list threads it is "supervising"?

rtkit obviously knows which threads it is "supervising", since it spams syslog with messages like rtkit-daemon[1277]: Supervising 3 threads of 2 processes of 1 users. However, the nefarious little thing doesn't seem to provide a way to list those…
usretc
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7
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1 answer

"tail -f" using "tcpdump -r"

To display content of pcap file , we use : tcpdump -r /Path/to/syscontection.pcap; However, this command line does not follow the pcap file on realtime , like tail -f which follows a plain text . Is there an option with tcpdump which acts like…
Abdennour TOUMI
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6
votes
1 answer

Real Time Local File Sync

How can I set up an instant file sync for two local directories? The catch is I need it in real time (15, 10 or even 5 seconds is too slow), and I don't want the target root directory created. For example, something similar to... cp -fr sourcea/*…
Adrian Schneider
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6
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1 answer

Record time of every process or thread context switch

I'm trying to get the nearest to real-time processing I can with a Raspbian distribution on a Raspberry Pi for manipulating its GPIO pins. I want to get a "feel" for the kind of performance I can expect. I was going to do this by writing a simple C…
Jodes
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6
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1 answer

How to sort ps output to find processes realtime priority and identify processess currently occupied running queue

How to properly identify real-time processes currently occupied CPU queue and count them using ps? I know there is a bunch of fileds like prio,rtprio,pri,nice but do not know correct to use. It seems I need use something like ps -eo…
user3417815
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6
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2 answers

What does the change of the clocksource influence?

The output of cat /sys/devices/system/clocksource/clocksource0/available_clocksource lists the available hardware clocks. I have changed the clocks, without any visible difference. sudo /bin/sh -c 'echo acpi_pm > current_clocksource' What are the…
TheMeaningfulEngineer
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5
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2 answers

Using sched_rt_period_us for setting maximum time between task calls of order of 10ms

I realize sched_rt_period_us and sched_rt_runtime_us are meant to prevent freezing the system in case of runaway RT task. I wonder though, if it's possible to use a small value of sched_rt_period_us to assure the task is running smoothly. I have a…
SF.
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