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Unable to grep the process

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Top Forums Shell Programming and Scripting Unable to grep the process
# 15  
Old 12-06-2016
Bug
Quote:
Originally Posted by rbatte1
You are probably hitting the problem that you script is only showing as a bash process like me:-

Session 1:-
Code:
$ cat /tmp/robinsleep.sh 
sleep 888

$ /tmp/robinsleep.sh

Session 2:
Code:
$ ps -ef|grep sleep
rbatte1 21561 21560  0 11:47 pts/9    00:00:00 sleep 888
rbatte1 21563 21537  0 11:47 pts/10   00:00:00 grep sleep
$ ps -fp 21560
UID        PID  PPID  C STIME TTY          TIME CMD
rbatte1 21560 21516  0 11:47 pts/9    00:00:00 bash
$

Robin
k... whats the solution ?
# 16  
Old 12-06-2016
Well, that depends on what the overall process is. What are you trying to work out?

For instance:-
  • Are you trying to ensure you only have one copy of a script running at a time?
  • Do you have different scripts that must not run together?
  • Are you trying to raise alerts with script overrunning?

if we can understand the context, then we may be able to suggest a better solution that will be flexible and let you evolve and support the code for the future.



Robin
# 17  
Old 12-06-2016
Interesting difference between script with "shebang" and one without:

Code:
cat shsleep1
#! /bin/bash
sleep 888

./shsleep1

ps -efH
.
.
.
  3272  3219  0  80   0 -  5698 wait   10:38 pts/3    00:00:00               /bin/bash
  4423  3272  0  80   0 -  3518 wait   13:12 pts/3    00:00:00                 /bin/bash ./shsleep1
  4424  4423  0  80   0 -  2205 hrtime 13:12 pts/3    00:00:00                   sleep 888


cat shsleep2
sleep 888

./shsleep2

ps -efH
.
.
.
  3272  3219  0  80   0 -  5698 wait   10:38 pts/3    00:00:00               /bin/bash
  4588  3272  0  80   0 -  5701 wait   13:15 pts/3    00:00:00                 /bin/bash
  4589  4588  0  80   0 -  2205 hrtime 13:15 pts/3    00:00:00                   sleep 888

I didn't realize that before.
Does it help you to shift a shebang into your script?
These 5 Users Gave Thanks to RudiC For This Post:
drl MadeInGermany mohtashims rbatte1 vgersh99
# 18  
Old 12-06-2016
Seems to be a SysV thing. I reproduced this behavior on HP-UX and AIX.
If there is no shebang, the execve() does not change the args, so they remain from the previous fork() i.e. are a copy from the invoking shell.
# 19  
Old 12-06-2016
Tools
Quote:
Originally Posted by RudiC
Interesting difference between script with "shebang" and one without:

Code:
cat shsleep1
#! /bin/bash
sleep 888

./shsleep1

ps -efH
.
.
.
  3272  3219  0  80   0 -  5698 wait   10:38 pts/3    00:00:00               /bin/bash
  4423  3272  0  80   0 -  3518 wait   13:12 pts/3    00:00:00                 /bin/bash ./shsleep1
  4424  4423  0  80   0 -  2205 hrtime 13:12 pts/3    00:00:00                   sleep 888


cat shsleep2
sleep 888

./shsleep2

ps -efH
.
.
.
  3272  3219  0  80   0 -  5698 wait   10:38 pts/3    00:00:00               /bin/bash
  4588  3272  0  80   0 -  5701 wait   13:15 pts/3    00:00:00                 /bin/bash
  4589  4588  0  80   0 -  2205 hrtime 13:15 pts/3    00:00:00                   sleep 888

I didn't realize that before.
Does it help you to shift a shebang into your script?
If i remove #! /bin/bash from the script other commands are getting affected. So, I need #! /bin/bash else my script fails for other reasons.

The reason i wrote the script is only to check if the script is running as a process or not.

What can be done ?
Last edited by Don Cragun; 12-06-2016 at 11:10 PM.. Reason: Remove duplicated text.
# 20  
Old 12-07-2016
The shebang must be there!
Code:
$ cat myscript
#! /bin/bash
$ sleep 888
./myscript &
[1] 7164
$ pgrep -l myscript
 7164 myscript

# 21  
Old 12-07-2016
Can I draw you back to the questions in post 16? There might be a better way to achieve your overall goal rather than to be looking for processes all over the place. You might consider the risks that someone viewing the script may create a process that is matched by your grep, which could cause results to be unpredictable.



Robin
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