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| <h3 class="section">27.5 Orphaned Process Groups</h3> |
| |
| <p><a name="index-orphaned-process-group-3212"></a> |
| When a controlling process terminates, its terminal becomes free and a |
| new session can be established on it. (In fact, another user could log |
| in on the terminal.) This could cause a problem if any processes from |
| the old session are still trying to use that terminal. |
| |
| <p>To prevent problems, process groups that continue running even after the |
| session leader has terminated are marked as <dfn>orphaned process |
| groups</dfn>. |
| |
| <p>When a process group becomes an orphan, its processes are sent a |
| <code>SIGHUP</code> signal. Ordinarily, this causes the processes to |
| terminate. However, if a program ignores this signal or establishes a |
| handler for it (see <a href="Signal-Handling.html#Signal-Handling">Signal Handling</a>), it can continue running as in |
| the orphan process group even after its controlling process terminates; |
| but it still cannot access the terminal any more. |
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