Capturing stdout and stderr in C or C++ program
如果將 Tcl 內嵌在 C 或者 C++ 程式內，程式用來獲取 Tcl stdout 輸出的方法。下面是我使用 clang-format 編排，並且為了練習將 -buffering 從 none 改為 line 的程式。
#include <iostream>
#include <cstring>
#include <tcl.h>
//
// Example class to catch stdout and stderr channel output.
//
// In the real world, this would be a GUI class (in Qt, KWWidgets etc)
// that makes the proper API calls to display the output in the right
// widget.
class TclIOCatcher {
public:
void outputText(const char *buf, int toWrite) {
std::cout << "-----TclIOCatcher--------------" << std::endl;
std::cout.write(buf, toWrite);
std::cout << "---------------------" << std::endl;
}
};
//
// Tcl is pure C, and this is a C++ program; to ensure proper
// calling linkage, encapsulate callbacks in a extern "C" section.
extern "C" {
// outputproc is callback used by channel to handle data to outpu
static int outputproc(ClientData instanceData, CONST84 char *buf, int toWrite,
int *errorCodePtr) {
// instanceData in this case is a pointer to a class instance
TclIOCatcher *qd = reinterpret_cast<TclIOCatcher *>(instanceData);
qd->outputText(buf, toWrite);
return toWrite;
}
// inputproc doesn't do anything in an output-only channel.
static int inputproc(ClientData instancedata, char *buf, int toRead,
int *errorCodePtr) {
return TCL_ERROR;
}
// nothing to do on close
static int closeproc(ClientData instancedata, Tcl_Interp *interp) { return 0; }
// no options for this channel
static int setoptionproc(ClientData instancedata, Tcl_Interp *interp,
CONST84 char *optionname, CONST84 char *value) {
return TCL_OK;
}
// for non-blocking I/O, callback when data is ready.
static void watchproc(ClientData instancedata, int mask) {
/* not much to do here */
return;
}
// gethandleproc -- retrieves device-specific handle, not applicable here.
static int gethandleproc(ClientData instancedata, int direction,
ClientData *handlePtr) {
return TCL_ERROR;
}
// Tcl Channel descriptor type.
// many procs can be left NULL, and for our purposes
// are left so.
Tcl_ChannelType TclChan = {
"tclIOTestChan", /* typeName */
TCL_CHANNEL_VERSION_4, /* channel type version */
closeproc, /* close proc */
inputproc, /* input proc */
outputproc, /* output proc */
NULL, /* seek proc - can be null */
setoptionproc, /* set option proc - can be null */
NULL, /* get option proc - can be null */
watchproc, /* watch proc */
gethandleproc, /* get handle proc */
NULL, /* close 2 proc - can be null */
NULL, /* block mode proc - can be null */
NULL, /* flush proc - can be null */
NULL, /* handler proc - can be null */
NULL, /* wide seek proc - can be null if seekproc is*/
NULL /* thread action proc - can be null */
};
}
int main(int argc, char **argv) {
Tcl_FindExecutable(argv[0]);
// create instance of the Tcl interpreter
Tcl_Interp *interp(Tcl_CreateInterp());
Tcl_Init(interp);
// class object to catch output
TclIOCatcher test;
// create a new channel for stdout
Tcl_Channel m_Out =
Tcl_CreateChannel(&TclChan, "testout", &test, TCL_WRITABLE);
//
// IMPORTANT -- tcl Channels do buffering, so
// the output catcher won't get called until a buffer
// is filled (default 4K bytes).
// These settings are stolen from TkWish.
Tcl_SetChannelOption(NULL, m_Out, "-translation", "lf");
Tcl_SetChannelOption(NULL, m_Out, "-buffering", "line");
Tcl_SetChannelOption(NULL, m_Out, "-encoding", "utf-8");
//
// make this new channel the standard output channel.
Tcl_SetStdChannel(m_Out, TCL_STDOUT);
//
// I'm not sure why this is necessary, but apparently it has
// something to do with how reference counting inside the interpeter works.
Tcl_RegisterChannel(0, m_Out);
//
// do all the same stuff for stderr. In our case, we push the
// output all to the same place, but you could handle it seperately.
Tcl_Channel m_Err =
Tcl_CreateChannel(&TclChan, "testerr", &test, TCL_WRITABLE);
Tcl_SetChannelOption(NULL, m_Err, "-translation", "lf");
Tcl_SetChannelOption(NULL, m_Err, "-buffering", "line");
Tcl_SetChannelOption(NULL, m_Err, "-encoding", "utf-8");
Tcl_SetStdChannel(m_Err, TCL_STDERR);
Tcl_RegisterChannel(0, m_Err);
//
// run one command to demonstrate how it works
const char testcommand[] = "puts [info patchlevel]";
int result = Tcl_EvalEx(interp, testcommand, strlen(testcommand), 0);
// show the result, should be zero.
std::cout << "Result = " << result << std::endl;
Tcl_Finalize();
exit(result);
}
然後撰寫一個簡單的 CMakeLists.txt 來使用 CMake 幫忙編譯程式：
cmake_minimum_required(VERSION 3.12 FATAL_ERROR)
# set the project name
project(capture VERSION 1.0 LANGUAGES CXX)
set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED True)
# find_package (TclStub REQUIRED)
find_package(TCL REQUIRED)
# add the executable
add_executable(capture capture.cpp)
target_link_libraries (capture ${TCL_LIBRARY})
include_directories (${TCL_INCLUDE_PATH})
