Passing a Command to Unix in Ada

Passing a Command to Unix in Ada

[Robert T. Sagris]

I was wondering if there are any functions similar to the system 
command in C available in Ada. Also I was wondering if there was 
a similar function as rename in Ada.

If you could give a translation for the following lines it would be
most appreciated. *THIS IS NOT HOMEWORK* I am trying to rewrite a little
program I wrote in C to Ada but don't no were to look. I have looked
through Ada, as a Second Language by Cohen and found nothing
useful for this problem

Well here are the lines.

/*The Header files for the functions*/
#include <stdio.h>
#include <stdlib.h>

main() {
...

/* In particular how would I cobble together some arbitrary string
   made up of string and integer variables. */
sprintf(command, "ls *%i.%s", some_integer, some_string);

/* Is there some equivalent command available in Ada's standard
   packages? */
system(command);

/* I know of the file handling functions in Ada.Text_IO such as
   Create, Open, Close, Delete etc.. but no Rename. (Is there on?)
*/
rename(old_file_name_string, new_file_name_string);

}

Well I hope this doesn't seem to simplistic but I found if I am
to general in my questions I get answer that assume I know more
about programming in Ada than I do.

Well thanks for any help you can give me.

Robbi Sagris

Re: Passing a Command to Unix in Ada

[Thomas Preymesser]

Hi Robert,

On Sat, 06 Feb 1999 16:20:34 -0500, "Robert T. Sagris"
<robs@physics.BLAH.purdue.BLAH.edu> wrote:

>I was wondering if there are any functions similar to the system 
>command in C available in Ada. 

there's an example at my Ada-page at: 

	<http://www.geocities.com/SiliconValley/Park/6549/>


-- 
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Re: Passing a Command to Unix in Ada

[dennison]

In article <36BCB222.EF9B4FF7@physics.BLAH.purdue.BLAH.edu>,
  "Robert T. Sagris" <robs@physics.BLAH.purdue.BLAH.edu> wrote:
> I was wondering if there are any functions similar to the system
> command in C available in Ada. Also I was wondering if there was

(sigh.)

There is no "system" command in C. Many OS'es have a system call named
"system" that does what you describe, providing you link in the proper OS
library. OS routines can be used in Ada by declaring their subprogram
specification and following it up with a "pragma import" statement. Linking
in OS libraries is a compiler-specific thing; consult your compiler docs for
more information.

This is similar to C, except for the "pragma" part. C just *assumes* that any
function you declared but didn't complete will be linked in later. That makes
calling OS routines like "system" a bit simpler, but it also can cause
problems linking when the developer forgets to code a routine.

T.E.D.

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Re: Passing a Command to Unix in Ada

[Larry Kilgallen]

In article <79q8n7$u00$1@nnrp1.dejanews.com>, dennison@telepath.com writes:

> A couple of folks have written to me to point out that "system", although not
> a proper statement like "break" and "for", is indeed required to exist for C
> implementations by the ANSI C standard. So I must apologize for causing any
> confusion there.

Does anybody know what this required call does on a Macintosh ?

Larry Kilgallen

Re: Passing a Command to Unix in Ada

[David C. Hoos, Sr.]

Robert T. Sagris wrote in message <36BCB222.EF9B4FF7@physics.BLAH.purdue.BLAH.edu>...
>I was wondering if there are any functions similar to the system
>command in C available in Ada. Also I was wondering if there was
>a similar function as rename in Ada.
>
>If you could give a translation for the following lines it would be
>most appreciated. *THIS IS NOT HOMEWORK* I am trying to rewrite a little
>program I wrote in C to Ada but don't no were to look. I have looked
>through Ada, as a Second Language by Cohen and found nothing
>useful for this problem
>

Here is a library function which interfaces to the C library "system" function, followed by a little test program to execute it.

This should serve to illustrate how to interface to _any_ C library function.

Strictly speaking, this technique does not "pass a command to Unix" -- rather it interfaces to the C library.  In the case of
Execute_Shell_Command which interfaces to the C "System" command, I gave it the name I did for two reasons, viz.:

    1.  The name "System" cannot be used in Ada for a
        user-defined entity, because it's a language-defined
        package.

    2.  The name Execute_Shell_Command is more descriptive
        of what it actually does.  In some contexts, a program
        which executes a shell command is considered a security
        risk, so I make what it's doing more obvious.

---- begin Ada source code ----
with Ada.Characters.Latin_1;
with System;
function Execute_Shell_Command
           (The_Command : String) return Integer is
   function Execute
              (The_Command_Address : System.Address) return Integer;
   pragma Import (C, Execute, "system");
   The_Nul_Terminated_Command_String : constant String :=
     The_Command & Ada.Characters.Latin_1.Nul;
begin
   return Execute (The_Nul_Terminated_Command_String'Address);
end Execute_Shell_Command;
with Ada.Command_Line;
with Ada.Text_Io;
with Execute_Shell_Command;
procedure Test_Execute_Shell_Command is
   Status : Integer;
begin
   Ada.Text_Io.Put_Line
     ("Program """ & Ada.Command_Line.Command_Name &
      """ is executing the shell command """ &
      Ada.Command_Line.Argument (1) & """");
   Status := Execute_Shell_Command (Ada.Command_Line.Argument (1));
   Ada.Text_Io.Put_Line
     ("Function "" Execute_Shell_Command"" returned" &
      Integer'Image (Status));
end Test_Execute_Shell_Command;
---- end Ada source code ----

Re: Passing a Command to Unix in Ada

[dennison]

In article <36C06B04.3E2D7A1F@physics.BLAH.purdue.BLAH.edu>,
  "Robert T. Sagris" <robs@physics.BLAH.purdue.BLAH.edu> wrote:
> I'm sorry my terminology was a bit off when I wrote this.
> I meant the system function in stdlib.h.
> If its not in there I don't know how my c program should work.
> The only header file this program includes are stdio.h and stdlib.h.
> So, it would seem system and rename are not being called be a  OS
> specific libraries. Am misinterpreting the std part in stdlib as meaning
> STANDARD or am I confused.
>
> dennison@telepath.com wrote:
> >
> > In article <36BCB222.EF9B4FF7@physics.BLAH.purdue.BLAH.edu>,
> >   "Robert T. Sagris" <robs@physics.BLAH.purdue.BLAH.edu> wrote:
> > > I was wondering if there are any functions similar to the system
> > > command in C available in Ada. Also I was wondering if there was

> > There is no "system" command in C. Many OS'es have a system call named

A couple of folks have written to me to point out that "system", although not
a proper statement like "break" and "for", is indeed required to exist for C
implementations by the ANSI C standard. So I must apologize for causing any
confusion there.

But the point is that it is a library routine that should be callable from
any language that knows how to link to it, not a command unique to C that is
unavailable outside of it. On the Unix system I have access to it is located
in libc.a. Ada has a standard way of importing C routines. The trick is
linking to libc.a, which you will have to consult your compiler docs to
figure out how to do. If you have trouble figuring it out, post specifics
(compiler/Platform/OS) and someone here may be able to help out.


T.E.D.

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Re: Passing a Command to Unix in Ada

[dennison]

In article <36C06B04.3E2D7A1F@physics.BLAH.purdue.BLAH.edu>,
  "Robert T. Sagris" <robs@physics.BLAH.purdue.BLAH.edu> wrote:
> I'm sorry my terminology was a bit off when I wrote this.
> I meant the system function in stdlib.h.
> If its not in there I don't know how my c program should work.
> The only header file this program includes are stdio.h and stdlib.h.
> So, it would seem system and rename are not being called be a  OS
> specific libraries. Am misinterpreting the std part in stdlib as meaning
> STANDARD or am I confused.
>
> dennison@telepath.com wrote:
> >
> > In article <36BCB222.EF9B4FF7@physics.BLAH.purdue.BLAH.edu>,
> >   "Robert T. Sagris" <robs@physics.BLAH.purdue.BLAH.edu> wrote:
> > > I was wondering if there are any functions similar to the system
> > > command in C available in Ada. Also I was wondering if there was

> > There is no "system" command in C. Many OS'es have a system call named

A couple of folks have written to me to point out that "system", although not
a proper statement like "break" and "for", is indeed required to exist for C
implementations by the ANSI C standard. So I must apologize for causing any
confusion there.

But the point is that it is a library routine that should be callable from
any language that knows how to link to it, not a command unique to C that is
unavailable outside of it. On the Unix system I have access to it is located
in libc.a. Ada has a standard way of importing C routines. The trick is
linking to libc.a, which you will have to consult your compiler docs to
figure out how to do. If you have trouble figuring it out, post specifics
(compiler/Platform/OS) and someone here may be able to help out.

Also, some compiler implementations provide an interface to "system" out of
the box...


T.E.D.

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Re: Passing a Command to Unix in Ada

[Robert T. Sagris]

I'm sorry my terminology was a bit off when I wrote this.
I meant the system function in stdlib.h.
If its not in there I don't know how my c program should work.
The only header file this program includes are stdio.h and stdlib.h.
So, it would seem system and rename are not being called be a  OS
specific libraries. Am misinterpreting the std part in stdlib as meaning
STANDARD or am I confused.

dennison@telepath.com wrote:
> 
> In article <36BCB222.EF9B4FF7@physics.BLAH.purdue.BLAH.edu>,
>   "Robert T. Sagris" <robs@physics.BLAH.purdue.BLAH.edu> wrote:
> > I was wondering if there are any functions similar to the system
> > command in C available in Ada. Also I was wondering if there was
> 
> (sigh.)
> 
> There is no "system" command in C. Many OS'es have a system call named
> "system" that does what you describe, providing you link in the proper OS
> library. OS routines can be used in Ada by declaring their subprogram
> specification and following it up with a "pragma import" statement. Linking
> in OS libraries is a compiler-specific thing; consult your compiler docs for
> more information.
> 
> This is similar to C, except for the "pragma" part. C just *assumes* that any
> function you declared but didn't complete will be linked in later. That makes
> calling OS routines like "system" a bit simpler, but it also can cause
> problems linking when the developer forgets to code a routine.
> 
> T.E.D.
> 
> -----------== Posted via Deja News, The Discussion Network ==----------
> http://www.dejanews.com/       Search, Read, Discuss, or Start Your Own

Re: Passing a Command to Unix in Ada

[Lieven Marchand]

kilgallen@eisner.decus.org (Larry Kilgallen) writes:

> Does anybody know what this required call [system] does on a Macintosh ?
> 

Actually, ANSI C requires that there exists a function system() in the
library. system(NULL) should return whether it does something useful
on the platform. system(Arbitrary_String) is implementation
defined. So my first guess would be that on the Macintosh, system
systematically returns an error, which is a completely conformant
implementation.

-- 
Lieven Marchand <mal@bewoner.dma.be> 
------------------------------------------------------------------------------
Few people have a talent for constructive laziness. -- Lazarus Long

Re: Passing a Command to Unix in Ada

[Steven Hovater]

If you're using something like Apex, you can access the POSIX implementation to do
an exec etc. Let me know if you need sample code -

Cheers,
Steve


"Robert T. Sagris" wrote:

> I'm sorry my terminology was a bit off when I wrote this.
> I meant the system function in stdlib.h.
> If its not in there I don't know how my c program should work.
> The only header file this program includes are stdio.h and stdlib.h.
> So, it would seem system and rename are not being called be a  OS
> specific libraries. Am misinterpreting the std part in stdlib as meaning
> STANDARD or am I confused.
>
> dennison@telepath.com wrote:
> >
> > In article <36BCB222.EF9B4FF7@physics.BLAH.purdue.BLAH.edu>,
> >   "Robert T. Sagris" <robs@physics.BLAH.purdue.BLAH.edu> wrote:
> > > I was wondering if there are any functions similar to the system
> > > command in C available in Ada. Also I was wondering if there was
> >
> > (sigh.)
> >
> > There is no "system" command in C. Many OS'es have a system call named
> > "system" that does what you describe, providing you link in the proper OS
> > library. OS routines can be used in Ada by declaring their subprogram
> > specification and following it up with a "pragma import" statement. Linking
> > in OS libraries is a compiler-specific thing; consult your compiler docs for
> > more information.
> >
> > This is similar to C, except for the "pragma" part. C just *assumes* that any
> > function you declared but didn't complete will be linked in later. That makes
> > calling OS routines like "system" a bit simpler, but it also can cause
> > problems linking when the developer forgets to code a routine.
> >
> > T.E.D.
> >
> > -----------== Posted via Deja News, The Discussion Network ==----------
> > http://www.dejanews.com/       Search, Read, Discuss, or Start Your Own

--
Steven Hovater
svh@rational.com
Software Engineering Consultant
Phone/fax:781-676-2565/2500
Rational Software
Pager: 888-906-2209
83 Hartwell Ave, Lexington, MA                                             Amateur
radio: AA1YH

Re: Passing a Command to Unix in Ada

[robert_dewar]

In article <36CDCC36.630D3811@mediaone.net>,
  Steven Hovater <nh-ho@mediaone.net> wrote:
> If you're using something like Apex, you can access the
> POSIX implementation to do an exec etc. Let me know if
> you need sample code -

You hardly need POSIX for this, just interface to the
standard exec function in the normal manner using pragma
Import.


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