stdlib/atexit.3

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  36 .\"     @(#)atexit.3    8.1 (Berkeley) 6/4/93
  37 .\" $FreeBSD: src/lib/libc/stdlib/atexit.3,v 1.10 2002/12/18 13:33:03 ru Exp $
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  39 .Dd May 20, 2008
  40 .Dt ATEXIT 3
  41 .Os
  42 .Sh NAME
  43 .Nm atexit
  44 .Nd register a function to be called on exit
  45 .Sh SYNOPSIS
  46 .In stdlib.h
  47 .Ft int
  48 .Fn atexit "void (*func)(void)"
  49 #ifdef UNIFDEF_BLOCKS
  50 .Ft int
  51 .Fn atexit_b "void (^block)(void)"
  52 #endif
  53 .Sh DESCRIPTION
  54 The
  55 .Fn atexit
  56 function
  57 registers the function
  58 .Fa func
  59 to be called at program exit, whether via
  60 .Xr exit 3
  61 or via return from the program's
  62 .Fn main .
  63 Functions so registered are called in reverse order;
  64 no arguments are passed.
  65 #ifdef UNIFDEF_BLOCKS
  66 .Pp
  67 The
  68 .Fn atexit_b
  69 function is like
  70 .Fn atexit
  71 except the callback is a block pointer instead of a function pointer.
  72 .Bd -ragged -offset indent
  73 Note: The
  74 .Fn Block_copy
  75 function (defined in
  76 .In Blocks.h )
  77 is used by
  78 .Fn atexit_b
  79 to make a copy of the block, especially for the case when a stack-based
  80 block might go out of scope when the subroutine returns.
  81 .Ed
  82 #endif
  83 .Pp
  84 These callbacks must not call
  85 .Fn exit ;
  86 if it should be necessary to terminate the process while in such a
  87 function, the
  88 .Xr _exit 2
  89 function should be used.
  90 (Alternatively, the callbacks may cause abnormal
  91 process termination, for example by calling
  92 .Xr abort 3 . )
  93 .Pp
  94 At least 32 callbacks can always be registered;
  95 more are allowed as long as sufficient memory can be allocated.
  96 .\" XXX {ATEXIT_MAX} is not implemented yet
  97 .Sh RETURN VALUES
  98 #ifdef UNIFDEF_BLOCKS
  99 .ds ATEXIT_B atexit_b
 100 #endif
 101 .Rv -std atexit \*[ATEXIT_B]
 102 .Sh ERRORS
 103 .Bl -tag -width Er
 104 .It Bq Er ENOMEM
 105 No memory was available to add the function to the list.
 106 The existing list of functions is unmodified.
 107 .El
 108 .Sh SEE ALSO
 109 .Xr exit 3
 110 .Sh STANDARDS
 111 The
 112 .Fn atexit
 113 function
 114 conforms to
 115 .St -isoC .