Linux perform regular tasks to achieve every second

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Linux perform regular tasks to achieve every second

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The following is only my work, the learning process into contact with the contents of deficiencies like him to bear.

crontab scheduled task minimum cycle of 1 minute, if the scheduling period script requires less than 1 minute, crontab can not be used directly, but can be implemented to schedule period less than one minute using the following method.
date >> /root/result.txtThe timing for the command execution needed (of course, the statement can be replaced by other scripts, if necessary) with a period of 1 second, achieved in two steps:
1, to achieve 1 minute cycle carried out 60;
2, the crontab regular tasks per minute test.sh execute a script
steps 1 and 2 used in conjunction to achieve the date >> /root/result.txtimplementation of demand once per second command.

Script writing /root/test.sh

This method is applicable to the case of the scheduling period can be divisible 60

#!/bin/bash
step=1
for (( i = 0; i < 60; i = (i+step) )); do
    date >> /root/result.txt
    sleep $step
done

exit 0

Configuration regular tasks

The timing task is configured to be performed once every minute
if not to learn how to add a scheduled task, refer to Linux's command crontab

// 编辑crontab
crontab -e
// 添加定时任务
* * * * * sh /root/test.sh
或
*/1 * * * * sh /root/test.sh

Achieve results

Through the above steps, you can be realized date >> /root/result.txtcommand once every second, the test results are as follows:

Other knowledge involved

Clear file contents mode

method one:

cat /dev/null > file.name

Second way:
This approach will write a blank line in the file

echo "" > file.name

Three ways: in vi / vim edit mode, using %dempty

vim file.name
:%d
:wq

Appended to the end of the input file

// > 添加内容，会删除文件中的原来内容
date > /root/result.txt
// >> 在原文件末尾追加内容
date >> /root/result.txt

reference

• Three ways to empty the contents of the file linux
• Linux Append command to the end of the file
• linux how to perform regular tasks crontab realize every second!