Shulou(Shulou.com)06/03 Report--

This article mainly introduces how to write shell, has a certain reference value, interested friends can refer to, I hope you read this article after a great harvest, the following let Xiaobian take you to understand.

Quote: I haven't written shell scripts myself before, either because I'm lazy or because I'm not pushed to write shells. However, some time ago, work requirements required re-running several months of scripts, which were run regularly every day, and several scripts were run together every day. You might say, it's too easy, write a loop, and then let him run by himself. Yes, you can easily write loops in your programming language, such as PHP. But, you know, that actually changes the structure of the code, and who knows what that might lead to? Also, I don't guarantee that I understand all the code inside! So, the question is, how do you cycle through these months without changing the original code? Yes, that is, simulate the real runtime situation, passing in the date parameter you need to receive (provided that your code already has this door)! You know, these timed scripts have an elegant name, crontab, so it's shell, and all you have to do is write shell.

Have you ever written a shell? It doesn't matter. You obviously already know that after the requirements are determined. It's too simple. Isn't it just grammar? Don't tell me you can't Google, can't Baidu!

I'll throw a few points to consider first, and then give the code directly!

How do you get the current time and convert it to the format you need? Keyword: date

How to prevent running the same content multiple times at the same time? Keyword: lock

3. How to cool down the execution after the program runs once? Keywords: sleep

How do I specify a running time period, counter, or start date? Keywords: while, let, expr

5. Additional: How to know the current operation status? Keywords: echo , progress

Consider these problems, you will write it step by step, do not know the syntax, directly Google, Baidu, code reference is as follows:

#/bin/bash# @author: youge# @date: 2015-12-22startDate="2015-11-24" # when to start startDateTimestamp=`date -d "$startDate" +%s`endDate="2015-12-14" # when to endendDateTimestamp=`date -d "$endDate" +%s`sleepTime=25 # to take a breakhaveSthUndo=0 # check if there is something undo , if not , exit the programrootDir='/cygdrive/d/wamp/ppi/'dir=$rootDir"cron/"itemArr=("itemA" "itemB" "itemC") # the items you want to run therefor item in ${itemArr[@]}do runFile=$rootDir$item".run"; if [ ! -f "$runFile" ] ; then haveSthUndo=1; echo $item" runs on me" $runFile " touched"; echo -e "script startTime: "`date "+%Y-%m-%d %H:%M:%S"` "\nbeginDate:" $startDate "\nendDate:" $endDate "\npath:" $dir >> $runFile touch "$runFile"; break; else echo $item "is runing, skipped. " $runFile; fidone;if [ $haveSthUndo -ne 1 ]; then echo -e "Nothing to do now ...\ ncheck it... "; exit;fiecho "haveSthUndo eq: " $haveSthUndo;while [[ $endDateTimestamp -ge $startDateTimestamp ]]do runDate=`date -d @$startDateTimestamp +%Y-%m-%d`; #1987-01-06 params="item=$item&d=$runDate"; msg="[`date "+%Y-%m-%d %H:%M:%S"`] now we run the date: "${runDate}" [params]: "${params}; echo $msg; # to show me ... echo $msg >> $runFile; # run the scripts below cd $dir && /bin/php ./ script1.php $params && /bin/php ./ script2.php $params && /bin/php ./ scriptx.php $params # run the scripts upon startDateTimestamp=`expr $startDateTimestamp + 86400`; # run the next day ... echo " ___sleeping for $sleepTime seconds ... "; x=''; for ((itime=0; itime> $runFile;#end of the file

Appendix:

According to my initial shell, the problems encountered are listed below, hoping to reduce the time for everyone to take detours:

1, the whole shell script, in fact, is equivalent to a series of commands you enter in the terminal, if you want to do anything in the shell, first think about what you can do in the terminal, the connection of characters, is directly with "" double quotes, output, variable definition without $sign, but must be added when using $sign.

2,"=" assignment symbol, there must be no spaces on both sides, which is different from other languages, especially when you have your own code aesthetic style, otherwise you will report syntax errors!

3. The array contents in for are separated by spaces, not commas

4, conditional judgment [ true ] square brackets need to have a space, but there can be no space between two square brackets, such as [[ true ]]

5, while conditional judgment can be used () brackets, can also be used [[ ]] brackets

6, if you write shell with windows, be sure to pay attention to the newline format\n instead of\r\n, you need to use some editors (such as notepad++) to change the newline format!

Finally: In fact, language is just a tool, never too difficult (too difficult and no one will use ah), the real tool to work, is your mind!

Just do it.

[ root @my-pc ]$ sh urScripts.sh #see you next time Thank you for reading this article carefully. I hope that the article "How to write shell" shared by Xiaobian will help everyone. At the same time, I hope everyone will support you a lot. Pay attention to the industry information channel. More relevant knowledge is waiting for you to learn!

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