:(){ :|:&amp; };:    If you enter this into your terminal CPU/memory usage will spike out of control instantly and trigger an infinite loop.
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I looked at  and can't understand how this works.  This command "exponentially spawns subprocesses until your box locks up".  But why? What I understand less are the colons.  user@host$ :(){ :|:&amp; };:
73904
When is it a good idea to use ?  I sometimes see this in code samples of PHP. Does this handle DOS/Mac/Unix endline issues?
65415
I have 4GB RAM. When I open Firefox, IntelliJ IDEA or VS Code and some other application my memory is about used up thus my machine hangs and I can't do anything. I can't even close any applications.    Date and time are shown in the top bar so that I can view it any time without any thing typing.   If I would view memory status in this way without typing anything then I can make a decision whether to open an application or whether this application may put my machine in hanging state or not.    Is it possible in Ubuntu 18.04 LTS?
12751
Various constructions can cause TeX (aka the lion) to go into an infinite loop. The simplest example is \def~{~}~, which defines ~ to expand to itself, then expands it. Now, if we exclude macro expansion, getting a loop is more difficult. With pure TeX, the two shortest methods I found (without macros) are  \everypar{\the\everypar}. \toksdef~0~{\the~}\the~.   (including the trailing dots); note that the second is not macro expansion, but the expansion of \the\toks0 in hiding. With eTeX, I got down to  \if\unexpanded\fi   which has the additional "quality" of being expandable. Here, \unexpanded could be replaced by \detokenize or \scantokens.   Why does that trigger an infinite loop? Is there a similarly short TeX constructions which does not use macro expansion (preferably only primitives)?
28430
I have problem (seems to be trivia) about Ubuntu Terminal. Once my network connection slow down then it (sometimes but very rare to happened) showed some information like this.     I shocked because I have been got 2,919 PB/s. Sorry my mouse block some part of letter 'P' (I actually rush to print screen) but I believe you can recognize it.    EDIT    based on answer given to me, and I got similar info then, I'd like to add more clearly new image after.    Can someone explain it to me?  Best Regards!
77625
So I have a program written in C++.  It can tell me how long it took to do all the calculations and it does a lot of quite heavy, multi-threaded calculation.   I've just noticed that if I run the program on the exact same machine, it takes around 20-21 seconds to do all the calculations if started from the TTY, and only about 0.2 seconds if I start it from GNOME terminal.  What is causing that? It's literally the exact same file on the same machine.
17892
This is a follow-up to : ulimit and cgroups are not user friendly, and besides, wouldn't work with applications that spawn separate processes, such as Chrome/Chromium for each new (group of) tabs.  The simple and effective solution, used by Windows 7 actually, is to warn the user that the OS is running low on memory. This simple warning pop-up has prevented me from having any low-memory-caused system freeze in Windows, while I kept running into them on Ubuntu distros that I was testing live (where the RAM-mounted disk would eat up 2GB alone).  So, is there some way to automatically warn the user that the available RAM is nearing zero, without the user having to keep an eye on some memory monitoring gadget? Surely  could be configured to do that?
73550
Quick question: what is the compiler flag to allow g++ to spawn multiple instances of itself in order to compile large projects quicker (for example 4 source files at a time for a multi-core CPU)?
123628
I keep hearing that this is a huge no-no. Why is this? I run Ubuntu mostly so it doesn't affect me, but I was just wondering.
8656
I have noticed that from some time my system is freezing and its probably caused by the high CPU usage which is caused by the system process.  All applications I'm running is the Skype, TeamSpeak and Chrome so it definitely shouldnt eat that amount of CPU.  You can see the problem itself and running processes in the screenshot below:    Sometimes CPU usage is reaching 90%, but the average usage is like 40-65%.  My PC parameters:   Windows 8 (customer preview) Intel Core i3 - 2350M 8 GB RAM   I'd appreciate any help attempt! Regards.  --UPDATE--  As the user below posted a great answer, I have noticed that the process that is eating the most CPU in the system is called Arthurx.sys, simple google tells that it's a TPLink driver (an wifi adapter, I have bought like 2 weeks ago!) drivers has been installed from the Windows MSDN, but also tried to install the drivers from the attached CD, but it doesn't help. From the system start, it is using like 5% of the CPU only, but after 2-4 hours of working it is growing up and reaching 40-60% of the CPU usage.  Device name: TPLink WN722N
12311
CPU Cycles, Memory Usage, Execution Time, etc.?  Added: Is there a quantitative way of testing performance in JavaScript besides just perception of how fast the code runs?
54803
At first, the question seems to be a little bit silly/confusing as the OS does the job of managing process execution.  However, I want to measure how much some processes are CPU/IO-bound and I feel like my OS is interfering on my experiments with, for instance, scheduled OS processes.  Take as an example the following situation: I ran the process A twice and got the following output from the tool "time" (time columns in seconds):  +---+-------+---------+-----------+---------+ |Run|Process|User Time|System Time|Wall time| +---+-------+---------+-----------+---------+ |1  |A      |196.3    |5.12       |148.86   | |2  |A      |190.79   |4.93       |475.46   | +---+-------+---------+-----------+---------+   As we can see, although the user and sys time are similar, the elapsed time of both drastically changes (diff. of ~5 min). Feels like something in my environment caused some sort of contention.  I want to stop every possible background process/services to avoid any kind of noise during my experiments but I consider myself a novice/intermediate unix-user and I don't know how to guarantee this.  I'm using Linux 4.4.0-45-generic with Ubuntu 14.04 LTS 64 bit.  I really appreciate the assistance. If you guys need any missing information, I will promptly edit my post.  CPU Info  $ grep proc /proc/cpuinfo | wc -l 8 $ lscpu Architecture:          x86_64 CPU op-mode(s):        32-bit, 64-bit Byte Order:            Little Endian CPU(s):                8 On-line CPU(s) list:   0-7 Thread(s) per core:    2 Core(s) per socket:    4 Socket(s):             1 NUMA node(s):          1 Vendor ID:             GenuineIntel CPU family:            6 Model:                 60 Stepping:              3 CPU MHz:               4002.609 BogoMIPS:              7183.60 Virtualization:        VT-x L1d cache:             32K L1i cache:             32K L2 cache:              256K L3 cache:              8192K NUMA node0 CPU(s):     0-7
56639
#!/bin/bash  SUBJECT="WARNING CPU USAGE HIGH" TO=gmail id MESSAGE=/tmp/messages echo "#######################" &gt; $MESSAGE echo "CPU statistics as follows.." &gt;&gt; $MESSAGE mpstat &gt;&gt; $MESSAGE echo "#######################" &gt;&gt; $MESSAGE CPU_USAGE=$(top -b -n1 | awk '/^Cpu/ {print $2}' | cut -d. -f1) [ $CPU_USAGE -gt 85 ] &amp;&amp; mail -s "$SUBJECT" "$TO" &lt; $MESSAGE`   ./cpu.sh: line 11: [: -gt: unary operator expected What might be the reason
101072
I was curious and wanted to see if I could start Firefox using Terminal. So I typed   firefox   in Terminal, and it displayed the message below  (process:5199): GLib-CRITICAL **: g_slice_set_config: assertion 'sys_page_size == 0' failed   And Firefox started running. But I am a little worried because the message above looks like an error message to me. Can anyone tell me what it means?
30271
Yesterday I was copying a single, 8 GB file to a USB with a slow, 7 MB/s write speed, while my RAM is 3 GB. While copying the system froze, to the point where I couldn't even move the cursor.  I managed to log into the text console, and ran iotop, it showed that a process named kswapd0 was taking 99.99% of IO.  Are there workarounds so copying a large file doesn't make my system unusable?
14348
It's a situation that has happened quite often to me: after I press (with a different intention) Ctrl-S in a terminal, the interaction (input or output) with it is frozen. It's probably a kind of "scroll lock" or whatever.  How do I unfreeze the terminal after this?  (This time, I have been working with apt-shell inside a bash inside urxvt--not sure which of them is responsible for the special handling of Ctrl-S: I was searching the history of commands backwards with C-r, as usual for readline, but then I wanted to go "back" forwards through the history with the usual--at least in Emacs--C-s (, , ), but that caused the terminal to freeze. Well, scrolling/paging to view past things still works in the terminal, but no interaction with the processes run there.)
11663
I am looking for a way to clean up the mess when my top-level script exits.  Especially if I want to use set -e, I wish the background process would die when the script exits.