execute problems

Glenn Satchell Glenn.Satchell at uniq.com.au
Tue Sep 19 13:45:10 UTC 2006

>Date: Tue, 19 Sep 2006 10:30:32 +0200
>From: Jon Otterholm <jon.otterholm at ide.resurscentrum.se>
>To: dhcp-users at isc.org
>Subject: Re: execute problems
>There is not much info on these functions. I hope that someone out there 
>could share some working examples -  but the response on this list is 
>not overwhelming.
>muzzol wrote:
>> i'm interested in this new option. where can i find more information?
>> thx

man dhcp-eval
     execute(command-path, data-expr1 ... data-exprN);

       External command execution is made possible  through  exe-
       cute();  expressions.   These  expressions take a variable
       number of arguments, where the first is the  command  name
       (full path or only the name of the executable) and is fol-
       lowed by zero or more are  data-expressions  whose  values
       will   be  evaluated  and  passed  as  external  arguments
       (assumed  to  be  text  strings  suitable  for  use  as  a
       command-line  argument).   It  returns  the numeric return
       code of the external command, or one of the following spe-
       cial values:

       o 125: Invalid arguments.

       o 126: fork() failure

       o 127: execvp() failure

       o -SIGNAL: Should the child exit due to a  signal,  rather
         than  exiting  normally  with an exit status, the signal
         number multiplied by negative 1 will be returned.

       Execute is synchronous, and the program will  block  until
       the  external  command being run has finished. Please note
       that lengthy program execution (for  example,  in  an  "on
       commit"  in  dhcpd.conf) may result in bad performance and
       timeouts.  Only external applications with very short exe-
       cution times are suitable for use.

       Passing user-supplied  data  to  an  external  application
       might  be  dangerous.   Make sure the external application
       checks input buffers for  validity.   Non-printable  ASCII
       characters  will  be  converted  into  dhcpd.conf language
       octal escapes ("777"), make  sure  your  external  command
       handles them as such.

       It is possible to use the execute expression in  any  con-
       text, not only on events. If you put it in a regular scope
       in the configuration file you will  execute  that  command
       every time a scope is evaluated.

What particular type of information are you interested in?

Glenn Satchell       mailto:glenn.satchell at uniq.com.au  |  Heard about
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