Retrieving results from an external process

$Result = `ls *.sql`

which works perfectly well on any Unix (or Linux) system. The problem is that it doesn't work at all on Windows so, if you want your programme to be fully portable, you need a workaround. My solution is to use the one common feature on both Windows and Unix, the redirection character (>).

Say I want to run a SQL query (because this is something I do frequently, I have a subroutine for it)

# =======================================
# Runs an SQL file, returning the result.
# ---------------------------------------
# $_[0] is the connection string.
# $_[1] is the file to run.
# $_[2] is a file to write the result to.
# ---------------------------------------
# (This last is necessary because the ``
# syntax does not work in Windows.)
# =======================================
sub RunSqlQuery
{
   my $V_COMMAND = "sqlplus "
   . $C_SQLPLUS_FLAGS
   . " "
   . $_[0]
   ." \@"
   . $_[1]
   . " >"
   . $_[2];
   my $V_RESULT;

   # --------------------------------
   # Run the command created above...
   # --------------------------------
   TraceScript $Debug,
   "RunSqlQuery",
   "Running SQL Plus for [" . $_[1] . "]";
   TraceScript $Paranoid,
   "RunSqlQuery",
   "Connect string is [" . $V_COMMAND . "]";
   system $V_COMMAND;

   # ---------------------------------
   # Get the result back from the file
   # and send it up the call chain...
   # ---------------------------------
   $V_RESULT = ReadResultFile $_[2];
   TraceScript $Debug, "RunSqlQuery", "SQL query run, exiting.";
   return $V_RESULT;
}

Now the above piece of code will work, unaltered, on both Windows and Unix. Then all we need to get at the result is...

# ===============================================
# Reads a file in which a result has been placed.
# -----------------------------------------------
# $_[0] name of the file to read.
# -----------------------------------------------
# This is one of the workarounds made necessary
# because the syntax "VAR=`command`" does not
# work in Windows the same as it does in Unix.
# ===============================================
sub ReadResultFile
{
   my $V_BUFFER;

   TraceScript $Debug,
   "ReadResultFile",
   "About to read result file [" . $_[0] . "]";
   open(H_SQL_FILE, "<$_[0]") or die "FAILURE: Cannot open " . $_[0];
   read H_SQL_FILE, $V_BUFFER, 65535;
   close H_SQL_FILE;
   return $V_BUFFER;
}

The size limit of 65535 bytes is arbitrary and you may wish to alter it for your own requirements.