Opening a File for Appending

Opening a File for Appending

[Thomas Albrecht]

Does anyone know how to open a text file for appending.  I have
checked the Ada Manual in both Ch. 14 (Input/Output) and Ch.13
(system-dependent features) and have been unable to locate it.
Thanks in advance for you help.

-- Tom

========================================================================
==  Thomas Albrecht
==  Southwest Research Institute
==  San Antonio, Texas
==  TAlbrecht@swri.edu
========================================================================

Re: Opening a File for Appending

[David Weller]

In article <847@trident.datasys.swri.edu>,
Thomas Albrecht <TAlbrecht@SwRI.EDU> wrote:
>Does anyone know how to open a text file for appending.  I have
>checked the Ada Manual in both Ch. 14 (Input/Output) and Ch.13
>(system-dependent features) and have been unable to locate it.
>Thanks in advance for you help.
>

Um, in Ada95, one of the file modes is Append_File (for any of Text,
Sequential, Wide, and Stream_IO files).

Appending a file in Ada83 is OS dependent (unless the POSIX binding
supports this -- I'm not sure).


-- 
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	  For all sorts of interesting Ada95 tidbits, run the command:
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Re: Opening a File for Appending

[Steven B. Opdahl]

In article <3ejufu$g56@Starbase.NeoSoft.COM>,
David Weller <dweller@Starbase.NeoSoft.COM> wrote:
:
:Um, in Ada95, one of the file modes is Append_File (for any of Text,
:Sequential, Wide, and Stream_IO files).
:
:Appending a file in Ada83 is OS dependent (unless the POSIX binding
:supports this -- I'm not sure).

POSIX_IO supports this.  You need to add Append to the Open_Option_Set
before doing an Open, Open_Or_Create, or Set_File_Control.

Steve Opdahl

Re: Opening a File for Appending

[Keith Thompson]

In <3ejufu$g56@Starbase.NeoSoft.COM> dweller@Starbase.NeoSoft.COM (David Weller) writes:
> Um, in Ada95, one of the file modes is Append_File (for any of Text,
> Sequential, Wide, and Stream_IO files).
> 
> Appending a file in Ada83 is OS dependent (unless the POSIX binding
> supports this -- I'm not sure).

Yes it does, via the Form parameter of Text_IO.Open.

Here's a test/demo program; you can compile and execute it to find out
whether your implementation supports POSIX-style appending to a text file.

Note that it isn't necessary to explicitly "with" any POSIX packages;
POSIX specifies this behavior for the LRM-defined Text_IO package.

with Text_IO;
procedure Append_Test is
   File: Text_IO.File_Type;
   File_Name: constant String := "append.txt";
   Line1: constant String := "First line";
   Line2: constant String := "Second line";
   Ok: Boolean := True;
begin
   Text_IO.Create( File => File,
                   Mode => Text_IO.Out_File,
                   Name => File_Name );
   Text_IO.Put_Line(File, Line1);
   Text_IO.Close(File);

   Text_IO.Open( File => File,
                 Mode => Text_IO.Out_File,
                 Name => File_Name,
                 Form => "Append => True" );
   Text_IO.Put_Line(File, Line2);
   Text_IO.Close(File);

   declare
      S: String(1 .. 100);
      Last: Natural;
   begin
      Text_IO.Open( File => File,
                    Mode => Text_IO.In_File,
                    Name => File_Name );
      Text_IO.Get_Line(File, S, Last);
      if S(S'First .. Last) /= Line1 or Text_IO.End_Of_File(File) then
         Ok := False;
      else
         Text_IO.Get_Line(File, S, Last);
         if S(S'First .. Last) /= Line2 then
            Ok := False;
         end if;
      end if;
   exception
      when others =>
         Ok := False;
   end;

   begin
      Text_IO.Delete( File );
   exception
      when others => 
         Ok := False;
   end;

   if Ok then
      Text_IO.Put_Line("This implementation supports POSIX-style");
      Text_IO.Put_Line("appending to a text file via the Form parameter.");
   else
      Text_IO.Put_Line("This implementation does not support POSIX-style");
      Text_IO.Put_Line("appending to a text file via the Form parameter,");
      Text_IO.Put_Line("or some other problem occurred.");
   end if;

end Append_Test;

-- 
Keith Thompson (The_Other_Keith)  kst@thomsoft.com (kst@alsys.com still works)
TeleSoft^H^H^H^H^H^H^H^H Alsys^H^H^H^H^H Thomson Software Products
10251 Vista Sorrento Parkway, Suite 300, San Diego, CA, USA, 92121-2718
When you're a nail, every problem looks like a hammer.

Re: Opening a File for Appending

[Richard Riehle]

In a>In article <847@trident.datasys.swri.edu>,
>Thomas Albrecht <TAlbrecht@SwRI.EDU> wrote:
>>Does anyone know how to open a text file for appending.  I have
>>checked the Ada Manual in both Ch. 14 (Input/Output) and Ch.13
>>(system-dependent features) and have been unable to locate it.
>>Thanks in advance for you help.
>>
>
    Thomas -

       The good people at Alsys have provided a parameter for the
       formal argument, FORM, in the Text_IO.OPEN procedure that
       enables opening a file in APPEND mode.

       My VADS compiler manual does not indicate how to do this, but
       I may have an out-of-date VADS manual.

       In Ada 83/87 this is implementation-dependent. Thank you to
       designers of the new Ada standard for including an append
       capability in Ada.

    Richard Riehle
    email: adaworks@netcom.com