从另一个bash脚本内部选择性地打开和关闭bash脚本

Question

I have a Raspberry Pi running a bash script, eg, ScriptA, that calls a web function running on a cloud server and the function returns a value to the calling script. The cloud server contains a system where, visitors to the site are given a few options using buttons, eg, Button1, Button2 and Button3. The option selected by the visitor is sent by the web function to the calling bash script on the Pi as Request1, Request2 or Request3 for Button1, Button and Button3 respectively. The ScriptA keeps calling the web function recursively to check for any change in Request value. The value returned by the function to the Pi is then used to run another script on the Pi, eg, Request1 runs Script1, Request2 runs Script2 and Request3 runs Script3. Now, the webpage is dynamic and the visitor can click different options, one after the other, and the script running on the Pi also needs to change accordingly.

---

Button1 => Request1 |                              | Request1 => Script1
Button2 => Request2 | Cloud Server <=> Pi(ScriptA) | Request2 => Script2
Button3 => Request3 |                              | Request3 => Script3

---

What I have done is, I have used a switch case in the ScriptA to switch between the different scripts 1, 2 and 3. What I want is, as soon as the visitor to the site chooses a different option and the Pi receives the new request, the script for the previously selected option stops executing, and the script for the new request starts executing.

---

#!/bin/bash
# call.sh

while:
do
    req=$(curl -d "param=$param" http://www.example.net/req.php)
    case $req in
        *req1*)
            sudo sh /home/pi/stopscript2.sh
            sudo sh /home/pi/stopscript3.sh
            sudo sh /home/pi/startscript1.sh
            ;;
        *req2*)
            sudo sh /home/pi/stopscript1.sh
            sudo sh /home/pi/stopscript3.sh
            sudo sh /home/pi/startscript2.sh
            ;;
        *req3*)
            sudo sh /home/pi/stopscript1.sh
            sudo sh /home/pi/stopscript2.sh
            sudo sh /home/pi/startscript3.sh
            ;;
        esac
done

---

But, the problem with this piece of code is that, the first time the pi receives a request and starts executing the specific script for the incoming request, no more calls to the web function are made thereafter and the script continues executing the first request, regardless of whether the user has selected a new option or not.

How do I make it work as desired? I hope I could frame my question well enough.

Help is much welcome. Thanks in advance.

Answer 1

Assuming that:

1. we keep reading the new input and just execute the freshly gathered value, whether "Request1", "Reqest2" or "Request3" and get rid of the old one.
2. You don't mind previous process to be killed rather than to be stopped.

In addition to your approach, I have added the following:

1. A date,time print function, to demonstrate operation timing clearly. This can be omitted later one once functionality has been verified.

2. A 'getpid' function, which freshly calculates the pid of the previous running script and passes on to the kill function

3. To demonstrate this, I will be tailing a file data.txt which is continuously growing as 3 backgroud echo commands are continuously putting Request 1,2,3 into it. This will serve as our somewhat dynamic random input. A sample below.

Sample:

%_STATION@gaurav * /root/ga/shell> tail -f data.txt
Request2
Request1
Request1
Request1
Request3
Request2
Request1

The script output:

1. The line with EMPTY represents when no PID was found. EMPTY
2. This indicates a new request read from your file: [17-02-17 20:38:17|[>>>>NEW>>>REQUEST>> [Request3]>>>>]
3. [gaurav 82577 1 0 20:38 pts/3 00:00:00 sleep 11] . This is the old running process, so I will kill it now.
4. Its PID is captured: [OLDPID---->82577]
5. Once killed, a new one fired, and it is "Request3": [gaurav 82611 1 0 20:38 pts/3 00:00:00 sleep 13]
6. Now this keeps repeating. See the log below for more clarity.

A log excerpt:

17-02-17 20:38:16|EMPTY
17-02-17 20:38:16|[***NEWPROCESS***[82504]*****]
17-02-17 20:38:16|[>>>>NEW>>>REQUEST>> [Request1]>>>>]
17-02-17 20:38:16|gaurav    82504      1  0 20:38 pts/3    00:00:00 sleep 12
17-02-17 20:38:16|[OLDPID---->82504]
17-02-17 20:38:16|gaurav    82543      1  0 20:38 pts/3    00:00:00 sleep 11
17-02-17 20:38:16|[***NEWPROCESS***[82543]*****]
17-02-17 20:38:16|[>>>>NEW>>>REQUEST>> [Request1]>>>>]
17-02-17 20:38:16|gaurav    82543      1  0 20:38 pts/3    00:00:00 sleep 11
17-02-17 20:38:16|[OLDPID---->82543]
17-02-17 20:38:17|gaurav    82577      1  0 20:38 pts/3    00:00:00 sleep 11
17-02-17 20:38:17|[***NEWPROCESS***[82577]*****]
17-02-17 20:38:17|[>>>>NEW>>>REQUEST>> [Request3]>>>>]
17-02-17 20:38:17|gaurav    82577      1  0 20:38 pts/3    00:00:00 sleep 11
17-02-17 20:38:17|[OLDPID---->82577]
17-02-17 20:38:17|gaurav    82611      1  0 20:38 pts/3    00:00:00 sleep 13
17-02-17 20:38:17|[***NEWPROCESS***[82611]*****]
17-02-17 20:38:17|[>>>>NEW>>>REQUEST>> [Request2]>>>>]
17-02-17 20:38:17|gaurav    82611      1  0 20:38 pts/3    00:00:00 sleep 13
17-02-17 20:38:17|[OLDPID---->82611]
17-02-17 20:38:17|EMPTY
17-02-17 20:38:17|[***NEWPROCESS***[82664]*****]
17-02-17 20:38:17|[>>>>NEW>>>REQUEST>> [Request1]>>>>]
17-02-17 20:38:17|gaurav    82664      1  0 20:38 pts/3    00:00:00 sleep 12
17-02-17 20:38:17|[OLDPID---->82664]
17-02-17 20:38:17|gaurav    82699      1  0 20:38 pts/3    00:00:00 sleep 11
17-02-17 20:38:17|[***NEWPROCESS***[82699]*****]
17-02-17 20:38:17|[>>>>NEW>>>REQUEST>> [Request1]>>>>]
17-02-17 20:38:17|gaurav    82699      1  0 20:38 pts/3    00:00:00 sleep 11
17-02-17 20:38:17|[OLDPID---->82699]
17-02-17 20:38:18|gaurav    82733      1  0 20:38 pts/3    00:00:00 sleep 11
17-02-17 20:38:18|[***NEWPROCESS***[82733]*****]
17-02-17 20:38:18|[>>>>NEW>>>REQUEST>> [Request3]>>>>]
17-02-17 20:38:18|gaurav    82733      1  0 20:38 pts/3    00:00:00 sleep 11
17-02-17 20:38:18|[OLDPID---->82733]
17-02-17 20:38:18|gaurav    82767      1  0 20:38 pts/3    00:00:00 sleep 13
17-02-17 20:38:18|[***NEWPROCESS***[82767]*****]
17-02-17 20:38:18|[>>>>NEW>>>REQUEST>> [Request2]>>>>]

7. As seen in the above log, the script is now able to act according to the incoming requests. In your case, you can replace the tail -f data.txt | while read line tail -f data.txt | while read line line portion with while true; do while true; do and then put your curl command.

The script:

%_STATION@gaurav * /root/ga/shell> cat request_action.sh
#!/bin/bash

# configure your scirpts. Here I used Sleeps.
s1='sleep 11' ; s2='sleep 12' ; s3='sleep 13'

# DateTime and print function.
prnt()
{
  str="$1"
  dt=$(date +"%d-%m-%y "%T)
  [[ -z "$str" ]] && str="EMPTY"
  echo "$dt|$str"
}
# Function to generate PID of previous running script.
getpid()
{
  pid=$(ps -ef|egrep "$s1|$s2|$s3"|grep -v grep|awk '{print $2}')
  echo "$pid"
}
# To kill the existing running script/s.
stopnstart()
{
   prnt "$(ps -ef|egrep "$s1|$s2|$s3"|grep -v grep)"
   prnt "[OLDPID---->$(getpid)]"
   $(kill -9 $(getpid) 1>/dev/null 2>&1)    # Kill the old PID.
   $($1  1>/dev/null 2>&1 &)    # Now run the fresh script.
   prnt "$(ps -ef|egrep "$s1|$s1|$s3"|grep -v grep)"
   prnt "[***NEWPROCESS***[$(getpid)]*****]"
}

# Main loop
tail -f data.txt | while read line
do
     prnt "[>>>>NEW>>>REQUEST>> [$line]>>>>]"
      case $line in

          Request1)
                stopnstart "$s1"
                ;;
          Request2)
                stopnstart "$s2"
                ;;
          Request3)
                stopnstart "$s3"
                ;;
      esac
done
%_STATION@gaurav * /root/ga/shell>

I hope I got it right. Thanks.