"system()" vs "system_exec()" problem
- Posted by jjnick at cvn.com
Apr 29, 2001
This is a multi-part message in MIME format.
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I am pretty sure that the behavior of "system_exec()" is not desired:
=20
- "testargs.exe" will print a confirmation message that it found 2 =
arguments
- Calling "testargs.exe" with "system_exec()" with the following =
arguments: 'testargs "1 1" "2 2"' produces nothing . . .
- Yet, Calling "testargs.exe" with "system()" with the same arguments =
produces the correct result, "2"
=20
Test it out yourself with the following code:
=20
"TESTARGS.EXW"
include win32lib.ew
without warning
=20
constant Win =3D create( Window, "System calls", =
0, Default, Default, 170, 150, 0 ),
=20
SystemExecButton =3D create( PushButton, "Use system_exec()", =
Win, 10, 10, 140, 40, 0 ),
SystemButton =3D create( PushButton, "Use system()", =
Win, 10, 60, 140, 40, 0 )
=20
sequence OScommand
OScommand =3D "testargs \"1 1\" \"2 2\""
=20
global procedure onClick_SystemExecButton()
object result
result =3D system_exec(OScommand, 0)
result =3D message_box(sprintf( "%s", { "When testargs.exe is passed =
the following: 'testargs \"1 1\" \"2 2\"', nothing happens . . ." } ), =
"Test arguments", MB_ICONINFORMATION+MB_TASKMODAL )
end procedure =20
=20
global procedure onClick_SystemButton()
object result
=20
system (OScommand, 0)
result =3D message_box(sprintf( "%s", { "Yet, when testargs.exe is =
passed the same arguments: 'testargs \"1 1\" \"2 2\"', testargs.exe =
recognizes the 2 arguments" } ),
"Test arguments", MB_ICONINFORMATION+MB_TASKMODAL )
end procedure =20
=20
onClick[SystemExecButton] =3D routine_id( "onClick_SystemExecButton" )
onClick[SystemButton] =3D routine_id( "onClick_SystemButton" )
=20
WinMain( Win, Normal )
"TESTARGS.C"
=20
#include <stdio.h>
#include <stdlib.h>
=20
int main( int argc, char *argv[] ) {
=20
if ( argc =3D=3D 3 ) // argc is always at least "1"
printf("\nFound 2 arguments . . .\n");
getchar();
return( 0 );
}
As all of you know, including double quotes (") on the command line is =
perfectly legal under a DOS box . . .
Obviously, there is something with the way "system_exec()" processes =
double quotes (").
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<BODY>
<DIV><FONT face=3DArial size=3D2>I am pretty sure that the behavior of=20
"system_exec()" is not desired:<BR> <BR>- "<FONT=20
face=3D"Courier New">testargs.exe</FONT>" will print a confirmation =
message that=20
it found 2 arguments<BR>- Calling "<FONT face=3D"Courier =
New">testargs.exe</FONT>"=20
with "<FONT face=3D"Courier New">system_exec()</FONT>" with the =
following=20
arguments: <FONT face=3D"Courier New">'testargs "1 1" "2 2"</FONT>' =
produces=20
nothing . . .<BR>- Yet, Calling "<FONT face=3D"Courier =
New">testargs.exe</FONT>"=20
with "<FONT face=3D"Courier New">system()</FONT>" with the same =
arguments produces=20
the correct result, "2"<BR> <BR>Test it out yourself with the =
following=20
code:<BR> <BR>"TESTARGS.EXW"</FONT></DIV><FONT face=3DArial =
size=3D2>
<DIV><BR><FONT face=3D"Courier New" size=3D1>include =
win32lib.ew<BR>without=20
warning<BR> <BR>constant=20
Win &nbs=
p; =20
=3D create( Window, "System=20
calls", 0, Default, Default, =
170, 150,=20
0 ),<BR> <BR> =20
SystemExecButton =3D create( PushButton, "Use system_exec()",=20
Win, 10, 10, =
140, 40, 0 ),<BR> =20
SystemButton =3D create( PushButton, "Use=20
system()", =
Win, =20
10, 60, 140, 40, 0 =
)<BR> <BR>sequence=20
OScommand<BR>OScommand =3D "testargs \"1 1\" \"2 =
2\""<BR> <BR>global=20
procedure onClick_SystemExecButton()<BR> object =
result<BR> result =3D=20
system_exec(OScommand, 0)<BR> result =3D message_box(sprintf( "%s", =
{ "When=20
testargs.exe is passed the following: 'testargs \"1 1\" \"2 2\"', =
nothing=20
happens . . ." } ), "Test arguments", MB_ICONINFORMATION+MB_TASKMODAL =
)<BR>end=20
procedure &nbs=
p;  =
; =
=20
<BR> <BR>global procedure onClick_SystemButton()<BR> object=20
result<BR> <BR> system (OScommand, 0)<BR> result =3D=20
message_box(sprintf( "%s", { "Yet, when testargs.exe is passed the same=20
arguments: 'testargs \"1 1\" \"2 2\"', testargs.exe recognizes the 2 =
arguments"=20
} ),<BR> "Test arguments", MB_ICONINFORMATION+MB_TASKMODAL =
)<BR>end=20
procedure &nbs=
p;  =
; =
=20
<BR> <BR>onClick[SystemExecButton] =3D routine_id( =
"onClick_SystemExecButton"=20
)<BR>onClick[SystemButton] =3D routine_id(=20
"onClick_SystemButton" )<BR> <BR>WinMain( Win, Normal =
)</FONT></DIV>
<DIV><FONT face=3D"Courier New" size=3D1><BR><FONT face=3DArial=20
size=3D2>"TESTARGS.C"<BR></FONT> <BR>#include =
<stdio.h><BR>#include=20
<stdlib.h><BR> <BR>int main( int argc, char *argv[] )=20
{<BR> <BR> if ( argc =3D=3D 3 ) // argc is always at least=20
"1"<BR> printf("\nFound 2 arguments . . =
.\n");<BR> =20
getchar();<BR> return( 0 );<BR>}</FONT></FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>As all of you know, including double =
quotes (") on=20
the command line is perfectly legal under a DOS box . . .</DIV>
<DIV><BR>Obviously, there is something with the way "<FONT=20
face=3D"Courier New">system_exec()</FONT>" processes double quotes=20
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