notify(3) - Plan 9 from User Space

From adc93f6097615f16d57e8a24a256302f2144ec4e Mon Sep 17 00:00:00 2001 From: rsc Date: Fri, 14 Jan 2005 17:37:50 +0000 Subject: cut out the html - they're going to cause diffing problems. --- man/man3/notify.html | 183 --------------------------------------------------- 1 file changed, 183 deletions(-) delete mode 100644 man/man3/notify.html (limited to 'man/man3/notify.html') diff --git a/man/man3/notify.html b/man/man3/notify.html deleted file mode 100644 index 9899e701..00000000 --- a/man/man3/notify.html +++ /dev/null @@ -1,183 +0,0 @@ - -notify(3) - Plan 9 from User Space - - - - -

NOTIFY(3) NOTIFY(3) -

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-

NAME
- -
- - notify, noted, atnotify, noteenable, notedisable, notifyon, notifyoff - – handle asynchronous process notification
- -
-

SYNOPSIS
- -
- - #include <u.h> - #include <libc.h> - - - int notify(void (*f)(void*, char*)) - - - int noted(int v) - - - int atnotify(int (*f)(void*, char*), int in) - - - int noteenable(char *msg) - int notedisable(char *msg) - - - int notifyon(char *msg) - int notifyoff(char *msg) - -
-

DESCRIPTION
- -
- - When a process raises an exceptional condition such as dividing - by zero or writing on a closed pipe, a note is posted to communicate - the exception. A note may also be posted by another process via - postnote(3). On Unix, notes are implemented as signals. -
- - When a note is received, the action taken depends on the note. - See signal(7) for the full description of the defaults. -
- - The default actions may be overridden. The notify function registers - a notification handler to be called within the process when a - note is received. The argument to notify replaces the previous - handler, if any. An argument of zero cancels a previous handler, - restoring the default action. A fork(2) system call leaves the - handler registered in both the parent and the child; exec(3) restores - the default behavior. Handlers may not perform floating point - operations. -
- - After a note is posted, the handler is called with two arguments: - the first is unimplemented and should not be used (on Plan 9 it - is a Ureg structure giving the current values of registers); the - second is a pointer to the note itself, a null-terminated string. - -
- - A notification handler must finish either by exiting the program - or by calling noted; if the handler returns the behavior is undefined - and probably erroneous. Until the program calls noted, any further - externally-generated notes (e.g., hangup or alarm) will be held - off, and any further notes generated by erroneous - behavior by the program (such as divide by zero) will kill the - program. The argument to noted defines the action to take: NDFLT - instructs the system to perform the default action as if the handler - had never been registered; NCONT instructs the system to resume - the process at the point it was notified. In neither case - does noted return to the handler. If the note interrupted an incomplete - system call, that call returns an error (with error string interrupted) - after the process resumes. A notification handler can also jump - out to an environment set up with setjmp using the notejmp function - (see setjmp(3)). -
- - Unix provides a fixed set of notes (typically there are 32) called - signals. It also allows a process to block certain notes from - being delivered (see sigprocmask(2)) and to ignore certain notes - by setting the signal hander to the special value SIG_IGN (see - signal(2)). Noteenable and notedisable enable or disable receipt - of - a particular note by changing the current process’s blocked signal - mask. Receipt of a disabled note will be postponed until it is - reenabled. Notifyon and notifyoff enable or disable whether the - notification handler is called upon receipt of the note; if the - handler is not called, the note is discarded. -
- - Regardless of the origin of the note or the presence of a handler, - if the process is being debugged (see ptrace(2)) the arrival of - a note puts the process in the Stopped state and awakens the debugger. - -
- - Rather than using the system calls notify and noted, most programs - should use atnotify to register notification handlers. The parameter - in is non-zero to register the function f, and zero to cancel - registration. A handler must return a non-zero number if the note - was recognized (and resolved); otherwise it must return - zero. When the system posts a note to the process, each handler - registered with atnotify is called with arguments as described - above until one of the handlers returns non-zero. Then noted is - called with argument NCONT. If no registered function returns - non-zero, atnotify calls noted with argument NDFLT. -
- - The set of notes a process may receive is system-dependent, but - there is a common set that includes: -
- - -
- - Note                          Meaning               Unix signal
- interrupt                    user interrupt (DEL key)     SIGINTR
- hangup                       I/O connection closed      SIGHUP
- alarm                        alarm expired           SIGLARM
- quit                         quit from keyboard        SIGQUIT
- kill                         process requested to exit    SIGTERM
- sys: kill                    process forced to exit      SIGKILL
- sys: bus error                bus error              SIGBUS
- sys: segmentation violation    segmentation violation      SIGSEGV
- sys: write on closed pipe      write on closed pipe       SIGPIPE
- sys: child                    child wait status change     SIGCHLD
- -
- - -
- See /usr/local/plan9/src/lib9/await.c (sic) for the full list. - -
- - The notes prefixed sys: are usually generated by the operating - system.
- -
-

SOURCE
- -
- - /usr/local/plan9/src/lib9/notify.c - /usr/local/plan9/src/lib9/atnotify.c - -
-

SEE ALSO
- -
- - intro(3), notejmp in setjmp(3)
- -
- -

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