As a senior AnQi CMS website operation personnel, I am well aware that every script command detail may affect the stable operation of the service. For AnQiCMS'sstop.shScript, where aboutgrepWhen the command returns multiple PIDs,awkhow to handle it is indeed a technical point worth in-depth discussion, as it directly relates to whether the service can be stopped correctly.
In AnQiCMSstop.shIn the script, the command chain used to stop the AnQiCMS service core process is: ps -ef | grep '\<anqicms\>' | grep -v grep | awk '{printf $2}'
The purpose of this command chain is to find the main process ID (PID) of AnQiCMS from all running processes. Let's parse it step by step,awkCommand behavior in handling multiple PID cases.
Firstly,ps -efThe command will list the detailed information of all processes running in the system.This information typically includes users, PID, parent PID, CPU usage, startup time, and the full command path.
Next,grep '\<anqicms\>'Command willps -effilter the output of.\<and\>Are word boundary anchors in regular expressions, ensuringgrepExactly match the complete word “anqicms” rather than strings containing the word (such as “myanqicms” or “anqicms_test”), thus improving the accuracy of the match.
Then,grep -v grepIt is a very common operation. Due to the previousgrep 'anqicms'The command itself is also a running process, which contains the word 'grep'. If this step is not addedgrep -v grepThengrepThe process ID of the command itself is also included in the results, which is obviously not the target process we want to stop.grep -vThe function is to reverse match and exclude the lines that contain 'grep'.
The core issue lies in the last command in the pipeline:awk '{printf $2}'.awkis a powerful text processing tool, it reads input by line by default, and splits each line content into fields by spaces or other delimiters.ps -efThe output format of the second field ($2The value is usually the process ID (PID).
Whengrep -v greponly contains one line (i.e., only one AnQiCMS process is running) when, for example:user 1234 0.0 0.1 123456 7890 ? Ss Jul01 00:00:01 /path/to/anqicmsAt this time,awk '{printf $2}'will extract out1234，and output it as a string. Variableexistswill be correctly retrieved1234this PID.
However,grep -v grepThe output contains multiple lines (i.e., there are multiple AnQiCMS processes or related processes running), for example:user 1234 0.0 0.1 123456 7890 ? Ss Jul01 00:00:01 /path/to/anqicms instance1
user 5678 0.0 0.1 123456 7890 ? Ss Jul01 00:00:01 /path/to/anqicms instance2In this case,awkIt will process line by line. For the first line, it will output1234；For the second line, it will output5678。The key isprintfcommand. Withprintcommand is different,printfa newline character is not automatically added to the output content. Therefore,awk '{printf $2}'This will extract all the PIDsand concatenate them into a long string without any separators.
This means, if there are two PIDs1234and5678,awkthe output will be a single string12345678。This string will be assigned tostop.shscript, make sure it points to the correct directory of the AnQiCMS executable file, and that the directory containsexistsa variable.
Next, the script will executekill -9 $exists). WhenexistsThe value of12345678whenkill -9The command will try to kill a process with PID12345678It will not parse it askill -9 1234 5678, which will not recognize this long string as multiple independent PIDs. In most cases,12345678Such a PID may not exist, or even if it exists, it is not the actual process of AnQiCMS. Therefore, if there are multiple AnQiCMS processes running, this method of handling will lead tokill -9Command cannot effectively stop all AnQiCMS instances, and may even fail to stop any AnQiCMS instances, resulting in the AnQiCMS service not being able to stop completely.
Frequently Asked Questions
Q1:stop.shscript, make sure it points to the correct directory of the AnQiCMS executable file, and that the directory containsawk '{printf $2}'What situation would cause AnQiCMS to fail to stop completely?