pid | 易学教程

How to get the PID of a process that is piped to another process in Bash?

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问题 I am trying to implement a simple log server in Bash. It should take a file as a parameter and serve it on a port with netcat. ( tail -f $1 & ) | nc -l -p 9977 But the problem is that when the netcat terminates, tail is left behind running. (Clarification: If I don't fork the tail process it will continue to run forever even the netcat terminates.) If I somehow know the PID of the tail then I could kill it afterwards. Obviously, using $! will return the PID of netcat. How can I get the PID of

What is a .pid file and what does it contain?

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问题 I recently come across a file with the extension .pid and explored inside it but didn't find much. The documentation says: A Pid-File is a file containing the process identification number (pid) that is stored in a well-defined location of the filesystem thus allowing other programs to find out the pid of a running script. Can anyone shed more light on this, or guide me to details of what's contained in the pid file? 回答1: The pid files contains the process id (a number) of a given program.

Linux PID recycling

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问题 Is there any policy in Linux as to the recycling of used PIDs ? I mean, if a PId has been used, how much later will it be used again ? 回答1: As new processes fork in, PIDs will increase to a system-dependent limit and then wrap around. The kernel will not reuse a PID before this wrap-around happens. The limit (maximum number of pids) is /proc/sys/kernel/pid_max . The manual says: /proc/sys/kernel/pid_max (since Linux 2.5.34) This file specifies the value at which PIDs wrap around (i.e., the

Android - How to get the processName or packageName by using PID?

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问题 MY QUESTION: What could I use to retrieve the processName or packageName of a certain process given its PID ? Since in my task manager I wanted to use the PID while utilizing the killBackgroundProcesses code to kill the processes. Problem is I need the packageName/processName to do that and it would be such a hassle to the user if I asked them to type in the processName rather than just typing its PID. here's the image of my task manager: 回答1: Hello you can use this code, it works for me in

How to check if a process id (PID) exists

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问题 In a bash script, I want to do the following (in pseudo-code): if [ a process exists with $PID ]; then kill $PID fi What's the appropriate expression for the conditional statement? 回答1: To check for the existence of a process, use kill -0 $pid But just as @unwind said, if you're going to kill it anyway, just kill $pid or you will have a race condition. If you want to ignore the text output of kill and do something based on the exit code, you can if ! kill $pid > /dev/null 2>&1; then echo

What is the best way to ensure only one instance of a Bash script is running? [duplicate]

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问题 This question already has answers here : Quick-and-dirty way to ensure only one instance of a shell script is running at a time (39 answers) Closed 2 years ago . What is the simplest/best way to ensure only one instance of a given script is running - assuming it's Bash on Linux? At the moment I'm doing: ps -C script.name.sh > /dev/null 2>&1 || ./script.name.sh but it has several issues: it puts the check outside of script it doesn't let me run the same script from separate accounts - which I

Several ports (8080, 8009) required by Tomcat v9.0 Server at localhost are already in use.

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刚开始进行JavaWeb开发时可能会遇到这种错误。这是因为端口8080,8009这俩端口被占用了，所以需要找到这两个端口号对应进程，然后kill掉 win+R打开控制台 netstat -ano 找到进程对应的pid 最后一行是对应的pid 所以剩下的就好办了打开任务管理器找到目标pin对应的进程kill掉再打开就好了来源： CSDN 作者： Loganer 链接： https://blog.csdn.net/wyh1618/article/details/103551152

ubuntu上鼠标出现十字架解决方案

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原因是由于将terminal当成了python运行环境，直接输入import命令就会卡死，解决方法如下： 1.唤出terminal：ctrl + alt +t（如果有可用的terminal忽略此条） 2.找到import的进程号：输入 ps -A | grep import，显示信息的第一个数字应该就是pid 3.kill这个进程：kill -9 pid。之后就恢复了来源： CSDN 作者： nbxuwentao 链接： https://blog.csdn.net/nbxuwentao/article/details/103550110

RuntimeError: DataLoader worker (pid XXX) is killed by signal: Bus error 两种解决方案

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RuntimeError: DataLoader worker (pid XXX) is killed by signal: Bus error 两种解决方案第一种 ,权宜之计把代码中的 dataloader 改掉 num-worker改低不行就 = 1 试试第二种,docker的问题,docker分配的共享内存太少了查了上述错误原因：df -h查看，共享内存不足： docker内查到的/dev/shm共享内存真机的共享内存网上说的办法1，是docker run的时候加参数--shm-size，拿起不得重装？？现有container能否改这个size呢？查看这个 https://blog.csdn.net/shmily_lsl/article/details/81166951 找到容器对应的配置文件hostconfig.json，找到参数"ShmSize"，改！重启doker！！！搞定：参考: 链接：https://www.jianshu.com/p/4398bdb9e2d2 https://blog.csdn.net/shmily_lsl/article/details/81166951 来源： CSDN 作者： Longlongaaago 链接： https://blog.csdn.net/Willen_/article/details/103489485

java 性能问题排查与性能优化

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1. 代码相关遇到性能问题，首先应该做的是检查否与业务代码相关——不是通过阅读代码解决问题，而是通过日志或代码，排除掉一些与业务代码相关的低级错误。性能优化的最佳位置，是应用内部。譬如，查看业务日志，检查日志内容里是否有大量的报错产生，应用层、框架层的一些性能问题，大多数都能从日志里找到端倪（日志级别设置不合理，导致线上疯狂打日志）；再者，检查代码的主要逻辑，如 for 循环的不合理使用、NPE、正则表达式、数学计算等常见的一些问题，都可以通过简单地修改代码修复问题。 **别动辄就把性能优化和缓存、异步化、JVM 调优等名词挂钩，复杂问题可能会有简单解，「二八原则」在性能优化的领域里里依然有效。**当然了，了解一些基本的「代码常用踩坑点」，可以加速我们问题分析思路的过程，从 CPU、内存、JVM 等分析到的一些瓶颈点优化思路，也有可能在代码这里体现出来。下面是一些高频的，容易造成性能问题的编码要点。 1）正则表达式非常消耗 CPU（如贪婪模式可能会引起回溯），慎用字符串的 split()、replaceAll() 等方法；正则表达式表达式一定预编译。 2）String.intern() 在低版本（Java 1.6 以及之前）的 JDK 上使用，可能会造成方法区（永久代）内存溢出。在高版本 JDK 中，如果 string pool 设置太小而缓存的字符串过多