Command & Variable

karunesh · 04-07-2005, 08:08 AM

Hi Folks.

I am trying to write a shell script, in that I am reading some iptables commands in a variable form some txt file. Now I want to execute those commands using shell script. So here I am confused, how to do that !!

Can anyone help !

mcosta · 04-07-2005, 09:23 AM

SOME_COMMAND="echo this is a command"
$SOME_COMMAND
SOME_PARAMETERS="whatever you want"
echo $SOME_PARAMETERS

are you talking of that?

sirclif · 04-07-2005, 01:42 PM

if you have a string variable that is a command such as:

var="echo 'hello world'"

then you can execute the command represented by the string with exec

exec $var

mcosta · 04-08-2005, 05:19 AM

Quote:

Originally posted by sirclif
if you have a string variable that is a command such as:

var="echo 'hello world'"

then you can execute the command represented by the string with exec

exec $var

You are right, but doing so never goes back to the script, I mean:
[CODE]
var="echo 'hello world'"
exec $var
echo bye world
[CODE]
Does not executes the 'echo bye world'. 'exec' does not fork, it replaces the shell with the command.

rajniks · 04-08-2005, 05:53 AM

yup forking is one of the way of doing it .the parent process can fork() a child process...........i am also new to linux so dont know how exctlly to make that funcyion call.............but can be tried on that way.......................i will try doing it and post a reply later

mcosta · 04-08-2005, 06:54 PM

fork() is in c. In shell script there is no equivalent. I mean, when calling a comand, internally, bash makes fork+exec. But if you do 'exec command', only exec is called. So there is no more shell process, only the 'command' process.