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.TH EXITS 2
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.SH NAME
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exits, _exits, atexit, atexitdont, terminate \- terminate process, process cleanup
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.SH SYNOPSIS
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.B #include <u.h>
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.br
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.B #include <libc.h>
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.PP
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.nf
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.B
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void	_exits(char *msg)
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.B
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void	exits(char *msg)
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.PP
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.B
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int	atexit(void(*)(void))
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.PP
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.B
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void	atexitdont(void(*)(void))
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.fi
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.SH DESCRIPTION
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.I Exits
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is the conventional way to terminate a process.
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.I _Exits
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is the underlying system call.
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They
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can never return.
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.PP
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.I Msg
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conventionally includes a brief (maximum length
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.BR ERRLEN )
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explanation of the reason for
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exiting, or a null pointer or empty string to indicate normal termination.
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The string is passed to the parent process, prefixed by the name and process
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id of the exiting process, when the parent does a
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.IR wait (2).
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.PP
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Before calling
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.I _exits
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with
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.I msg
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as an argument,
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.I exits
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calls in reverse order all the functions
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recorded by
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.IR atexit .
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.PP
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.I Atexit
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records
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.I fn
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as a function to be called by
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.IR exits .
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It returns zero if it failed,
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nonzero otherwise.
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A typical use is to register a cleanup routine for an I/O package.
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To simplify programs that fork or share memory,
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.I exits
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only calls those
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.IR atexit -registered
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functions that were registered by the same
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process as that calling
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.IR exits .
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.PP
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Calling
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.I atexit
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twice (or more) with the same function argument causes
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.I exits
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to invoke the function twice (or more).
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.PP
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There is a limit to the number of exit functions
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that will be recorded;
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.I atexit
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returns 0 if that limit has been reached.
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.PP
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.I Atexitdont
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cancels a previous registration of an exit function.
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.SH SOURCE
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.B /sys/src/libc/port/atexit.c
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.SH "SEE ALSO"
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.IR fork (2),
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.IR wait (2)