Either this or you create a semaphore file: consider the following script stub:
This makes sure the script runs only one instance at a time.
I hope this helps.
bakunin
Not quite. There is a race condition between the time the existence test ([ -e "$fSemaphore" ]) is executed and the time the semaphore file is created (touch "$fSemaphore") that can allow two or more copies of this code to run simultaneously and not realize that another invocation is running.
This can be worked around with the shell's do not clobber option:
Note that both of these run a risk of leaving the semaphore file in place if the script is terminated by a kill signal (for the code above) or by any signal (for the code bakunin suggested). If this happens, the semaphore file will have to be manually removed before the script will run again successfully.
I am in need of some help; think I have confused myself.
Here is the issue I am faced with.
The script log file was fine, the nohup.out file has tens of thousands of lines like illegal use of sleep: sleep seconds
So I assume there is something with the seconds calculation in the script... (1 Reply)
Hi All I have a requiremnt to run a script inside another script.
here i am pulling the record count from the table in oracle.If record count is greater than 0 the script is executed.The scripts updates the count in the table and again the count is found out and the condition is checked and same... (3 Replies)
Hi Forum
Im using sleep in a while loop goes around 10 times. i feed it a variable with the time i what it to sleep for eg sleep $sleepVal and then print system date and time to screen but sometimes 1 second is added to the time why is this
here my code
sleepVal=5
while
do
... (3 Replies)
Hi All,
i am very new to shall script . i am not that much aware of sleep command ,
i want to terminate the sleep command after certain time.
following is my code.
while
loop
sleep 1800
messag=/status.sql
donethe script will be on sleep untill the messag be comes P. here my requirement... (4 Replies)
Hello,
Need a little help with the script below. I can't get it to sleep :( I'm trying to get this to check if the process is running and if it is, wait 10 secs and check again. Keep doing this until it's not running and then stop checking and send the email.
#!/bin/ksh
mailto=`cat... (2 Replies)
Hi Frnz,
I need to execute sleep command but i dont know the definite time.
Let me put my req:
I am running one shell script and this script creates some lock file in temp dir ...now in my script i want one function to go into sleep mode till this lock file exists..one lock file gone that... (6 Replies)
I need help in script.
I want my one script execute every time at 6:30 am and i have no cron access.
So i am putting sleep command there , Script may took half an hour 35 min , it depend upon queries how much it take time, but that is not issue,
So i want according to stop time of... (15 Replies)
Discussion started by: pallvi_mahajan
15 Replies
LEARN ABOUT PHP
sem_get
SEM_GET(3) 1 SEM_GET(3)sem_get - Get a semaphore idSYNOPSIS
resource sem_get (int $key, [int $max_acquire = 1], [int $perm = 0666], [int $auto_release = 1])
DESCRIPTION sem_get(3) returns an id that can be used to access the System V semaphore with the given $key.
A second call to sem_get(3) for the same key will return a different semaphore identifier, but both identifiers access the same underlying
semaphore.
PARAMETERS
o $key
-
o $max_acquire
- The number of processes that can acquire the semaphore simultaneously is set to $max_acquire.
o $perm
- The semaphore permissions. Actually this value is set only if the process finds it is the only process currently attached to the
semaphore.
o $auto_release
- Specifies if the semaphore should be automatically released on request shutdown.
RETURN VALUES
Returns a positive semaphore identifier on success, or FALSE on error.
CHANGELOG
+--------+-----------------------------------------+
|Version | |
| | |
| | Description |
| | |
+--------+-----------------------------------------+
| 4.3.0 | |
| | |
| | The $auto_release parameter was added. |
| | |
+--------+-----------------------------------------+
NOTES
Warning
When using sem_get(3) to access a semaphore created outside PHP, note that the semaphore must have been created as a set of 3 sema-
phores (for example, by specifying 3 as the nsems parameter when calling the C semget() function), otherwise PHP will be unable to
access the semaphore.
SEE ALSO sem_acquire(3), sem_release(3), ftok(3).
PHP Documentation Group SEM_GET(3)