Unix Programming - Need for sessions and process groups?

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Author Need for sessions and process groups?
Slash

2004-05-10, 5:44 pm

Why exactly do we need sessions and process groups in unix?

Besides being able to send signals to a group and manipulate a group
of processes all at once, is there any significant use of process
groups?

Why do we really *need* sessions?
Barry Margolin

2004-05-10, 5:44 pm

In article <341c1613.0405090857.1a6e7004@posting.google.com>,
debajit1@hotmail.com (Slash) wrote:

> Why exactly do we need sessions and process groups in unix?
>
> Besides being able to send signals to a group and manipulate a group
> of processes all at once, is there any significant use of process
> groups?


They're used extensively for job control by shells. Each job is a
separate process group, and a particular process group is designated as
foreground by associating its PGID with the terminal device.
Keyboard-generated signals are sent to that process group, and the
shell's "kill" command can send a signal to the entire group.

> Why do we really *need* sessions?


Sessions are necessary to keep track of all the processes in an
interactive login session.

--
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
David Schwartz

2004-05-10, 5:44 pm

Slash wrote:

> Why do we really *need* sessions?


A modem disconnects, which processes do you tell about it?

DS


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