Turn-shell Implementation Daemon

# #! There is a space followed by a space followed by the full path of the interpreter and must be correct.
#! /bin/ash

Pro_path= ""
# Testpro is an executable program to be guarded, which guarantees it is always running
Program= "Testpro"

# This script keeps looping,while< conditions > Do on one line to add a semicolon after the condition
# keywords or commands such as if, then, while, and do are the beginning of a new expression,
# The expression before a new expression must end with a newline character or a semicolon (;)
#如果条件不是单个常量或变量而是表达式的话, you need to enclose it in [].
The #while, until, and for loops both start with do to form the loop body as done
While true; Do
#休息10秒以确保要看护的程序运行起来了, this time depends on the actual situation

Sleep 10
The $ and \ characters in #单引号 ' are not referenced and escaped, but in double quotes "" is OK!
#单引号中如果还有单引号, all the single quotes are stripped out and the contents of the single quotation mark are output as they are.
# example: Echo ' has ' test '--and have test
# PS aux-->a to show other user-initiated processes;
# U is the user name and time to display the START process;
# x is the process for displaying the system itself;
# PS aux | grep executable name--in the resulting all process information text that is currently started,
# filter text lines that contain the specified text (which executes the program name)
# Note: Suppose PS aux | The grep executable name has output, but the output is not a letter but two,
A line of information text that #一个为查找到的包含有指定文本 (the name of the program can be executed) (a line of text ending with a newline character 0x10),
# One for the grep executable name, you lose yourself too,
# This message is not needed because we just want to know if the executable program that specified the name started
# GREP-V Specifies text-to-output line text information that does not contain the specified text
# wc-l The number of rows in the output file (------and output line break statistics)
# PS aux | grep $PROGRAM |grep-v grep | Wc-l---If a program with the specified program name starts, the result is greater than
pro_now= ' ps aux | grep $PROGRAM | grep-v grep | wc-l '

# Integer comparison:-lt, less than,-le, less than equals,-GT-greater than,-ge-> greater than equals,-eq, equals,-ne-> not equal to
# if [condition] and then put on one line to add a semicolon after the condition
#如果当前指定程序启动的个数小于壹的话
if [$PRO _now-lt 1]; Then
# 0, standard input,1-> standard output, 2-> standard error message output
#/dev/null-->linux's special file, it's like a bottomless pit, all the information redirected to it will disappear!
# 2->/dev/null redirect stderr to/dev/null,1>& 2-, redirect stdout to stderr,
#Starts the specified program directly, andDo not display any output
# The executable program is followed by a space plus a &amp, indicating that the program to be executed is running in the background
./$PROGRAM 2>/dev/null 1>&2&
# date >>./tinfo.log-directional output current datetime to file, add to end of file, if no file, create this file
Date>>./tinfo.log
#echo "Test Start" >> ./tinfo.log--> directed output test start added to end of file
echo "Test Start" >>.Tinfo. Log
# If Branch structure ends
fi

# basically the same as above, is more than a grept, the result is to filter out the information line containing T characters
#--and process stopped, D--and non-disruptive deep sleep, R--process running or ready,s--> to receive signal sleep,
#---has completely died, Z--has completely terminated
pro_stat= ' PS aux|grep $PROGRAM |grep t|grep-vgrep|wc-l '

#如果指定进程状态为已停止的信息大于零的话
if [$PRO _stat-gt 0]; Then
# killall--> to kill the process by name, -9--To send the program a signal value of 9, namely Sigkill (illegal hardware instructions)
#也可以不指定信号, the default is Sigterm, which is a signal value of 15
       killall-9 $PROGRAM
       Sleep 2
       ./$PROGRAM 2>/dev/null 1>&2&
       Date>>./tinfo.log
echo "Test Start" >>./tinfo. Log
fi
The #while, until, and for loops both start with do to form the loop body as done
Done
# exit is used to end the script and return the status value, 0-for success, not 0 for the error code, the value range is 0 ~ 255.
Exit 0

Turn-shell Implementation Daemon