A.10.3 Default Input, Output, and Error Files
Static Semantics
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.
procedure Set_Input(File : in File_Type);
Operates on a file of mode In_File. Sets the current
default input 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 In_File.
procedure Set_Output(File : in File_Type);
procedure Set_Error (File : in File_Type);
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.
function Standard_Input return File_Type;
function Standard_Input return File_Access;
Returns the standard
input file (see
A.10), or an access value
designating the standard input file, respectively.
function Standard_Output return File_Type;
function Standard_Output return File_Access;
Returns the standard
output file (see
A.10) or an access value
designating the standard output file, respectively.
function Standard_Error return File_Type;
function Standard_Error return File_Access;
{
8652/0052}
{
AI95-00194-01}
Returns the standard error file (see
A.10),
or an access value designating the standard error file, respectively.
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.
function Current_Input return File_Type;
function Current_Input return File_Access;
Returns the current
default input file, or an access value designating the current default
input file, respectively.
function Current_Output return File_Type;
function Current_Output return File_Access;
Returns the current
default output file, or an access value designating the current default
output file, respectively.
function Current_Error return File_Type;
function Current_Error return File_Access;
Returns the current
default error file, or an access value designating the current default
error file, respectively.
{
AI12-0130-1}
[The effect of Flush is the same as the corresponding subprogram in Sequential_IO
(see
A.8.2).] If File is not explicitly specified,
Current_Output is used.
Discussion: {
AI12-0052-1}
For the purpose of determining whether concurrent calls on text input-output
subprograms are required to perform as specified, subprograms that implicitly
operate on one of the default input-output files are considered to have
a parameter of Current_Input or Current_Output (as appropriate). The
result of Current_Output is considered to be overlapping with the file
given to the latest call of Set_Output (or Standard_Output if Set_Output
hasn't been called); a corresponding consideration applies to the result
of Current_Input. See the introduction of
Annex A
for details.
Erroneous Execution
{
8652/0053}
{
AI95-00063-01}
The execution of a program is erroneous if it invokes
an operation on a current default input, default output, or default error
file, and if the corresponding file object is closed or no longer exists.
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.
NOTE 1 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.
NOTE 2 The standard input, standard
output, and standard error files are different file objects, but not
necessarily different external files.
Wording Changes from Ada 95
{
8652/0051}
{
AI95-00057-01}
Corrigendum: Corrected the parameter mode of Flush; otherwise
it could not be used on Standard_Output.
{
8652/0053}
{
AI95-00063-01}
Corrigendum: Clarified that execution is erroneous only when a
closed default file is accessed.
Wording Changes from Ada 2012
{
AI12-0130-1}
Corrigendum: Moved the definition of Flush to
A.8.2,
as all input-output packages now have it.
Ada 2005 and 2012 Editions sponsored in part by Ada-Europe
