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Bug 000310

When Created: 01/01/2000 17:00:07
Against DJGPP version: 2.02
By whom: steve@effectivejava.com
Abstract: system() emulating echo mungs command line
The system() function's emulation of the shell's echo command operates incorrectly. If the text to be echoed contains a combination of + and \ symbols, then the command outputs garbage.

#include <cstdlib>
#include <iostream>

int main()
{
    const char* p = "echo c:\\dev\\c++\\p13";
    cout << p << '\n';
    system(p);
}

This produces the output:

echo c:\dev\c++\p13
c:\dev++\p13

Other commands lines containing plusses and backslashes, can produce garbage characters instead.

Note added: 01/07/2000 05:00:22
By whom: eliz@is.elta.co.il
I can only reproduce this with GNU `echo' (from GNU Sh-utils package).
So I'm guessing that the person who reported this has GNU Sh-utils installed.
Therefore, this isn't a DJGPP bug.

In fact, it isn't even a bug in GNU `echo', it's a feature!  GNU `echo' by
default interprets escape sequences in the string, unless invoked with the
-E switch.  (Unfortunately, the docs included with Sh-utils 1.12, which was
ported to DJGPP, lies about the default behavior and doesn't mention -E.)

Workaround added: 01/07/2000 05:00:04
By whom: eliz@is.elta.co.il
Several work-arounds:

  1) Rename echo.exe to something else.  Then `system' will invoke the
     internal command ECHO of COMMAND.COM.

  2) Invoke COMMAND.COM explicitly, like this:

     const char *p = "command.com /c echo c:\\dev\\c++\\p13";

  3) Invoke `echo' with the -E switch:

     const char *p = "echo -E c:\\dev\\c++\\p13";

  4) Use forward slashes instead of backslashes:

     const char *p = "echo c:/dev/c++/p13";

Closed on 01/07/2000 05:00:02: This is a feature of GNU `echo', not a DJGPP bug.
By whom: eliz@is.elta.co.il

Note added: 01/07/2000 06:00:17
By whom: eliz@is.elta.co.il
Oh, and by the way: `system' does NOT emulate the echo command.  This feature
is disabled in the sources and was never operational.



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