EXITS(3) EXITS(3)
NAME
exits, _exits, exitcode, atexit, atexitdont - terminate
process, process cleanup
SYNOPSIS
#include <u.h>
#include <libc.h>
void _exits(char *msg)
void exits(char *msg)
int exitcode(char *msg)
int atexit(void(*)(void))
void atexitdont(void(*)(void))
DESCRIPTION
Exits is the conventional way to terminate a process.
_Exits also terminates a process but does not call the reg-
istered atexit handlers (q.v.). They can never return.
Msg conventionally includes a brief (maximum length ERRLEN)
explanation of the reason for exiting, or a null pointer or
empty string to indicate normal termination. The string is
passed to the parent process, prefixed by the name and pro-
cess id of the exiting process, when the parent does a
wait(3).
Before calling _exits with msg as an argument, exits calls
in reverse order all the functions recorded by atexit.
Atexit records fn as a function to be called by exits. It
returns zero if it failed, nonzero otherwise. A typical use
is to register a cleanup routine for an I/O package. To
simplify programs that fork or share memory, exits only
calls those atexit-registered functions that were registered
by the same process as that calling exits.
Calling atexit twice (or more) with the same function argu-
ment causes exits to invoke the function twice (or more).
There is a limit to the number of exit functions that will
be recorded; atexit returns 0 if that limit has been
reached.
Atexitdont cancels a previous registration of an exit func-
tion.
SOURCE
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EXITS(3) EXITS(3)
/usr/local/plan9/src/lib9/atexit.c
/usr/local/plan9/src/lib9/_exits.c
SEE ALSO
fork(2), wait(3)
BUGS
Because of limitations of Unix, the exit status of a process
can only be an 8-bit integer. Exits and _exits treat null
or empty exit status as exit code 0 and call exitcode to
translate any other string into an exit code. By default,
the library provides an exitcode that maps all messages to
1. Applications may find it useful to provide their own
implementations of exitcode .
Exit codes 97 through 99 are used by the thread library to
signal internal synchronization errors between the main pro-
gram and a proxy process that implements backgrounding.
To avoid name conflicts with the underlying system, atexit
and atexitdont are preprocessor macros defined as p9atexit
and p9atexitdont; see intro(3).
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