[Spice-devel] [PATCH] Add utility to help redirecting output from remote-viewer/virt-viewer

[Frediano Ziglio]

These utility use some trick to use console even if they are GUI
application (not supposed to have a console by default).
This make output redirection harder as output by default will tend
to go to console of parent process instead of using redirected output.
This utility avoid remote-viewer/virt-viewer to see the calling process
console keeping the wanted redirection.

Signed-off-by: Frediano Ziglio <fziglio at redhat.com>
---
 src/Makefile.am               |  4 ++
 src/output-redirect-wrapper.c | 92 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 96 insertions(+)
 create mode 100644 src/output-redirect-wrapper.c

diff --git a/src/Makefile.am b/src/Makefile.am
index e76f5bc..01b9bc8 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -155,6 +155,10 @@ bin_PROGRAMS += windows-cmdline-wrapper
 windows_cmdline_wrapper_SOURCES = windows-cmdline-wrapper.c
 windows_cmdline_wrapper_LDFLAGS = -lpsapi
 
+bin_PROGRAMS += output-redirect-wrapper
+output_redirect_wrapper_SOURCES  = output-redirect-wrapper.c
+output_redirect_wrapper_CPPFLAGS = -DUNICODE -D_UNICODE
+
 virt-viewer_rc.$(OBJEXT): $(VIRT_VIEWER_RES) $(ICONDIR)/virt-viewer.ico
 	$(AM_V_GEN)$(WINDRES)				\
 		-DICONDIR='\"$(ICONDIR)\"'		\
diff --git a/src/output-redirect-wrapper.c b/src/output-redirect-wrapper.c
new file mode 100644
index 0000000..ed807bb
--- /dev/null
+++ b/src/output-redirect-wrapper.c
@@ -0,0 +1,92 @@
+/*
+ * Windows cmd: a command line wrapper for GUI applications
+ *
+ * Copyright (C) 2012-2016 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * Usage:
+ * This wrapper allows to redirect output even if your application
+ * tries to redirect its output to console.
+ *
+ * For instance you can use from console with a syntax like
+ *
+ *   output-redirect-wrapper remote-viewer.exe --debug > log.txt
+ *
+ * Based on Marc-André Lureau wrappers
+ */
+
+#include <windows.h>
+#include <stdio.h>
+#include <string.h>
+#include <tchar.h>
+
+int main(void)
+{
+    STARTUPINFO si = { 0, };
+    PROCESS_INFORMATION pi = { 0, };
+
+    // pass same input/output handles
+    si.cb = sizeof(si);
+    si.dwFlags = STARTF_USESTDHANDLES;
+    si.hStdInput  = GetStdHandle(STD_INPUT_HANDLE);
+    // redirect all to single output
+    si.hStdError = si.hStdOutput = GetStdHandle(STD_OUTPUT_HANDLE);
+    SetHandleInformation(si.hStdInput,  HANDLE_FLAG_INHERIT, HANDLE_FLAG_INHERIT);
+    SetHandleInformation(si.hStdOutput, HANDLE_FLAG_INHERIT, HANDLE_FLAG_INHERIT);
+
+    // parse command line, strip executable
+    TCHAR *cmdline = GetCommandLine();
+    cmdline += _tcsspn(cmdline, _T(" \t\v"));
+    TCHAR *end = _tcsstr(cmdline, cmdline[0] == _T('\"') ? _T("\" ") : _T(" "));
+    if (!end) {
+        fprintf(stderr, "Please pass executable to call\n");
+        return 1;
+    }
+    cmdline = end + 1;
+    cmdline += _tcsspn(cmdline, _T(" \t\v"));
+
+    // release console so program launched do not redirect to it
+    FreeConsole();
+
+    if (!CreateProcess(NULL,
+                       cmdline,
+                       NULL,           // Process handle not inheritable
+                       NULL,           // Thread handle not inheritable
+                       TRUE,           // Handle inheritance
+                       0,              // No creation flags
+                       NULL,           // Use parent's environment block
+                       NULL,           // Use parent's starting directory
+                       &si,
+                       &pi)) {
+        fprintf(stderr, "CreateProcess failed (%ld).\n", (long) GetLastError());
+        return 1;
+    }
+    // Close unneeded handle
+    CloseHandle(pi.hThread);
+
+    // Wait until child process exits.
+    WaitForSingleObject(pi.hProcess, INFINITE);
+
+    DWORD exit_code;
+    GetExitCodeProcess(pi.hProcess, &exit_code);
+
+    // Close process handle
+    CloseHandle(pi.hProcess);
+
+    // return same output of application
+    ExitProcess(exit_code);
+    return 0;
+}
-- 
2.5.0