A.10.3 Default Input, Output, and Error Files
Static Semantics
1
The following subprograms provide for the control
of the particular default files that are used when a file parameter is
omitted from a Get, Put, or other operation of text input-output described
below, or when application-dependent error-related text is to be output.
2
procedure Set_Input(File : in File_Type);
3
Operates on a file of mode In_File. Sets the
current default input file to File.
4
The exception
Status_Error is propagated if the given file is not open. The exception
Mode_Error is propagated if the mode of the given file is not In_File.
5
procedure Set_Output(File : in File_Type);
procedure Set_Error (File : in File_Type);
6
Each operates
on a file of mode Out_File or Append_File. Set_Output sets the current
default output file to File. Set_Error sets the current default error
file to File. The exception Status_Error is propagated if the given file
is not open. The exception Mode_Error is propagated if the mode of the
given file is not Out_File or Append_File.
7
function Standard_Input return File_Type;
function Standard_Input return File_Access;
8
Returns the standard
input file (see
A.10), or an access value
designating the standard input file, respectively.
9
function Standard_Output return File_Type;
function Standard_Output return File_Access;
10
Returns the standard
output file (see
A.10) or an access value
designating the standard output file, respectively.
11
function Standard_Error return File_Type;
function Standard_Error return File_Access;
12/1
{
8652/0052}
{
AI95-00194-01}
Returns the standard error file (see
A.10),
or an access value designating the standard
error output
file, respectively.
13
The Form strings implicitly
associated with the opening of Standard_Input, Standard_Output, and Standard_Error
at the start of program execution are implementation defined.
14
function Current_Input return File_Type;
function Current_Input return File_Access;
15
Returns the current
default input file, or an access value designating the current default
input file, respectively.
16
function Current_Output return File_Type;
function Current_Output return File_Access;
17
Returns the current
default output file, or an access value designating the current default
output file, respectively.
18
function Current_Error return File_Type;
function Current_Error return File_Access;
19
Returns the current
default error file, or an access value designating the current default
error file, respectively.
20/1
21
The effect of Flush is the same as the corresponding
subprogram in Streams.Stream_IO (see
A.12.1).
If File is not explicitly specified, Current_Output is used.
Erroneous Execution
22/1
{
8652/0053}
{
AI95-00063-01}
{erroneous execution (cause) [partial]}
The execution of a program is erroneous if it
invokes
an operation on attempts to use a
current default input, default output, or default error file
,
and if the corresponding file object is closed or that no longer exists.
22.a.1/1
Ramification: {
8652/0053}
{
AI95-00063-01}
Closing a default file, then setting the default
file to another open file before accessing it is not erroneous.
23/1
This paragraph was
deleted.{
8652/0053}
{
AI95-00063-01}
If the Close operation is applied to a file object
that is also serving as the default input, default output, or default
error file, then subsequent operations on such a default file are erroneous.
24
24 The standard input, standard output,
and standard error files cannot be opened, closed, reset, or deleted,
because the parameter File of the corresponding procedures has the mode
in out.
25
25 The standard input, standard output,
and standard error files are different file objects, but not necessarily
different external files.
Wording Changes from Ada 95
25.a/2
{
8652/0051}
{
AI95-00057-01}
Corrigendum: Corrected the parameter mode
of Flush; otherwise it could not be used on Standard_Output.25.b/2
25.c/2
{
8652/0053}
{
AI95-00063-01}
Corrigendum: Clarified that execution is
erroneous only when a closed default file is accessed.
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