Problem with looping construct Post: 302087907

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Top Forums Shell Programming and Scripting Problem with looping construct Post 302087907 by blowtorch on Thursday 7th of September 2006 04:34:04 AM

Old

09-07-2006

Registered User

OK, first of all, you should have an if condition there and not a while. Running this script will give you an infinite number of "Apache is still running..." outputs because the script only checks for apache running at the beginning and not in every iteration of the while loop. If you do want to use while, run the ps command inside the while loop.

Secondly, sleep. Use the sleep command so that your script does not hog system resources by constant condition checking.

Since you are using bash, you could rewrite the script like this:

Code:

while [ $(/usr/ucb/ps -axcu | /usr/bin/grep httpd > /dev/null; echo $?) -eq 0 ]; do 
   echo "running"; 
   sleep 10; 
done

Sleep for longer though...

blowtorch

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sleep

sleep(1)							   User Commands							  sleep(1)

NAME

       sleep - suspend execution for an interval

SYNOPSIS

   /usr/bin/sleep
       /usr/bin/sleep time

   ksh93
       sleep time

DESCRIPTION

   /usr/bin/sleep
       sleep suspends execution for at least the integral number of seconds specified by time.

   ksh93
       sleep suspends execution for at least the time in seconds specified by time or until a SIGALRM signal is received.

OPERANDS

   /usr/bin/sleep
       The following operands are supported for /usr/bin/sleep:

       time    time in seconds can be specified as a non-negative decimal integer number.

   ksh93
       The following operands are supported:

       time    Specify time in seconds as a floating point number. The actual granularity depends on the underlying system, normally around 1 mil-
	       lisecond.

EXAMPLES

       Example 1 Suspending Command Execution

       The following example executes a command after a certain amount of time:

	 example% (sleep 105; command)&

       Example 2 Executing a Command Every So Often

       The following example executes a command every so often:

	 example% while true
	 do
		 command
		 sleep 37
	 done

ENVIRONMENT VARIABLES

       See environ(5) for descriptions of the following environment variables that affect the execution of sleep: LANG, LC_ALL, LC_CTYPE,  LC_MES-
       SAGES, and NLSPATH.

EXIT STATUS

       The following exit values are returned:

       0     The execution was successfully suspended for at least time seconds, or a SIGALRM signal was received (see NOTES).

       >0    An error has occurred.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

   /usr/bin/sleep
       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Committed 		   |
       +-----------------------------+-----------------------------+
       |Standard		     |See standards(5). 	   |
       +-----------------------------+-----------------------------+

   ksh93
       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Uncommitted		   |
       +-----------------------------+-----------------------------+

SEE ALSO

       ksh93(1), wait(1), alarm(2), sleep(3C), wait(3UCB), attributes(5), environ(5), standards(5)

NOTES

       If the sleep utility receives a SIGALRM signal, one of the following actions is taken:

	   o	  Terminate normally with a zero exit status.

	   o	  Effectively ignore the signal.

       The sleep utility takes the standard action for all other signals.

SunOS 5.11							    20 Nov 2007 							  sleep(1)