Re: Yet another question on system calls(newbie question)

[James Rogers <jimmaureenrogers@worldnet.att.net>]

Torbj�rn Karfunkel wrote:
> 
> Using the pragma Import method of calling non-Ada entities, am I only
> allowed to define functions? How about procedures? What I want to do is
> to create a text file, give this text file as a parameter to a C
> program, and then wait until the C program finishes. By then it will
> have produced another text file that I want to use.
> Can I use a dummy result variable like the 'result' in the following
> (from another mail):
> 
> procedure Command is
> 
>    function C_System(value : String) return integer;
>    pragma Import(
>          C, C_System, "system");
> 
>    result : integer;
> begin
>    result := C_System("pwd ");
>    result := C_System(value => "acdsee D:\work\pictures\BP47.jpg ");
> end Command;
> 

Do you want to "use" the file with Ada, or with some other system
command?

Note that the "system" command in Unix can take a string containing
an entire pipeline, as in the following example:

   result := C_System("ps -ef | grep root");

You can also redirect the output of the command as follows:

   result := C_System("pwd > /tmp/here");

If you want to open a Unix pipe to a system call, and read the
result directly, then look at the example I posted on 
www.adapower.com for using the pipe command.

Note that your last proposal, to call the system command with the
name of an image file, will not work. The system command only
executes files that have executable permissions set. This is not
normally true for image files. 

Jim Rogers
Colorado Springs, Colorado USA