win32: user defined shell

This patch replaces the patch in win32.3 in the gnat collection.

The reasons for reworking that patch should be evident from
reading the patch below.

p5p-msgid: 199705291339.JAA21682@aatma.engin.umich.edu

2 files changed, 22 insertions, 10 deletions

diff --git a/pod/perlrun.pod b/pod/perlrun.pod
index c4679e1def..de7116d939 100644
--- a/pod/perlrun.pod
+++ b/pod/perlrun.pod
@@ -567,6 +567,17 @@ The command used to load the debugger code.  The default is:
 
 	BEGIN { require 'perl5db.pl' }
 
+=item PERL5SHELL (specific to WIN32 port)
+
+May be set to an alternative shell that perl must use internally for
+executing "backtick" commands or system().  Perl doesn't use COMSPEC
+for this purpose because COMSPEC has a high degree of variability
+among users, leading to portability concerns.  Besides, perl can use
+a shell that may not be fit for interactive use, and setting COMSPEC
+to such a shell may interfere with the proper functioning of other
+programs (which usually look in COMSPEC to find a shell fit for
+interactive use).
+
 =item PERL_DEBUG_MSTATS
 
 Relevant only if your perl executable was built with B<-DDEBUGGING_MSTATS>,
diff --git a/win32/win32.c b/win32/win32.c
index 7fb04166c2..57e90a2a8c 100644
--- a/win32/win32.c
+++ b/win32/win32.c
@@ -317,18 +317,19 @@ IdOS(void)
 static char *
 GetShell(void)
 {
-    static char* szWin95ShellEntry = "Win95Shell";
-    static char* szWin95DefaultShell = "Cmd32.exe";
-    static char* szWinNTDefaultShell = "cmd.exe";
-   
     if (!ProbeEnv) {
+	char* defaultshell = (IsWinNT() ? "cmd.exe" : "command.com");
+	/* we don't use COMSPEC here for two reasons:
+	 *  1. the same reason perl on UNIX doesn't use SHELL--rampant and
+	 *     uncontrolled unportability of the ensuing scripts.
+	 *  2. PERL5SHELL could be set to a shell that may not be fit for
+	 *     interactive use (which is what most programs look in COMSPEC
+	 *     for).
+	 */
+	char *usershell = getenv("PERL5SHELL");  
+
 	ProbeEnv = TRUE;
-	if (IsWin95()) {
-	    strcpy(szShellPath, szWin95DefaultShell);
-	}
-	else {
-	    strcpy(szShellPath, szWinNTDefaultShell);
-	}
+	strcpy(szShellPath, usershell ? usershell : defaultshell);
     }
     return szShellPath;
 }