T.S.Ravi Shankar wrote:
> Dear all :
>
> I see these lines in a perl program :
>
> $pif = fork;
> if($pid == 0) {
> exec("hpxy -s xxx.abc");
> }else{
> $pid1=wait;
> }
>
> I could understand that the fork is needed here to get into the child
> process "hpxy" !! What is the need for the "wait" here ?? When will
> the "else" loop be entered ??
After fork() there are two processes, parent and child. fork returns 0 to
the child, and the child's pid to the parent. So the "if" part is handling
the child, while the "else" part is handling the parent.
Basically, the child is exec()'ing a new program, while the parent is
calling wait(), which waits for the child to terminate.
The lines above are essentially equivalent to:
system("hpxy -s xxx.abc");
Unless there's something else going on in the program that we're not seeing,
system() should be used instead of the code above, IMO.
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