Process ID problem

[sdac]

Hi, below is code for a child process, i am trying to give it a group
ID which is +10 on the group ID of the parent process (writing a
simple shell here)
Somehow both print statements show same group ID as if setpgid has no
effect...

if((pid_child2=fork())==0)
{
printf("***hello from c2\n");

printf(" ***c2 gpid used to be %d\n", getpgid(0));
int pgpid = getpgid(0);
setpgid(0,pgpid+10);
printf(" ***c2 gpid was set to %d\n", getpgid(0));
..
..
..
}
SCREEN OUTPUT --->

***hello from c2
***c2 gpid used to be 15946
***c2 gpid was set to 15946
-------------------------

UPDATE:
both setpgid calls are returning -1 and errno EPERM.
Could this be due to the adding of 10 to pgpid ? is that
allowed. The reason i am picking this pgid (x+1) is because i have
two children processos and want them both to have same group ID as
each other, but yet different from there parent.

Any ideas ? Thanks

[Walter Roberson]

In article <11*********************@a75g2000cwd.googlegroups. com>,
sdac <am*****@gmail.comwrote:

>Hi, below is code for a child process, i am trying to give it a group
ID which is +10 on the group ID of the parent process (writing a
simple shell here)

Processes and group ids are not part of the C language, and are
artifacts of the operating system you are using. For assistance
with your difficulty, you should consult a group that specializes
in your operating system. Perhaps comp.unix.programming .
--
"It is important to remember that when it comes to law, computers
never make copies, only human beings make copies. Computers are given
commands, not permission. Only people can be given permission."
-- Brad Templeton

[Kenneth Brody]

sdac wrote:
[...]

printf(" ***c2 gpid used to be %d\n", getpgid(0));
int pgpid = getpgid(0);
setpgid(0,pgpid+10);
printf(" ***c2 gpid was set to %d\n", getpgid(0));

[...]

SCREEN OUTPUT --->

***hello from c2
***c2 gpid used to be 15946
***c2 gpid was set to 15946
-------------------------

UPDATE:
both setpgid calls are returning -1 and errno EPERM.

While most of the above is OT for clc, the fact that errno is
being set to EPERM is a major hint. Check the man pages on
setpgid() and see what could cause that error. If that doesn't
help, the you need to go to a group where this would be topical,
perhaps comp.unix.programming.

[Hint: many if the "set" calls like this do not allow arbitrary
values to be set. Consider, for example, "setuid(getuid()+1)".]

[...]

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