The following questions tend to be asked regularly on the comp.lang.tcl newsgroup:
At a high level, there are three different solutions to consider.
Replace the C/C++ main() with a tclsh/wish main program
Embed Tcl Calls in C/C++ code
While the text "Why adding Tcl calls to a C/C++ application is a bad idea" is an interesting dialog concerning the appropriate approach to performing this task, where can one find specific coding examples and documentation regarding what one needs to do, in a C program, if one needs to create an interpreter and then execute tcl commands making use of that interpreter.
Well, one example comes out of the box with both Tcl and Tk. Take a look at the tcl/unix/tclAppInit.c (or tcl/win/tclAppInit.c) files in the tcl source distribution (which is the mainline C module for the tclsh command), and in the Tk source distribution, tk/unix/tkAppInit.c or tk/win/winMain.c (I don't understand why the name difference here...). For MacOS, see tk/mac/tkMacAppInit.c and tk/macosx/tkMacOSXAppInit.c (again, I don't understand the reasoning for file name changes). These provide at least a basic skeleton for initializing an interpreter. Unfortunately, they leave you in an interpretive mode which most people don't want to happen. So another example is needed.
I do know there are two kinds of Tcl actions one can invoke from C/C++ Since Tcl is just a C library, some Tcl actions can be invoked by calling the appropriate Tcl function call.
However, some things in Tcl must be done by invoking Tcl_Eval, after appropriately setting up a Tcl interpreter.
Can someone provide some sample C or C++ code that shows setting up the interpreter, then perhaps invoking things each way?
A dream scenario would do this for Tcl/Tk since that is a superset of the same kind of request for Tcl...
AM Here is some (massaged) code that I use in one application. The idea is:
It does not use the Tcl script library, only the basic built-in commands are available, but this is a very simple set-up after all.
The function InitScript() is used to set up a script library private to the application and to get a functioning Tcl interpreter. The function EvalScriptCommand() is used elsewhere and simply wraps the details so that I do not need to use Tcl routines everywhere.
/* * Static global data */ static Tcl_Interp * tcl_interp ; /* Script interpreter */ int InitScript( void /* Nothing */ ) /* Return okay or not */ { char * pstr ; FILE * infile ; int retval ; int rc ; size_t filesize ; tcl_interp = Tcl_CreateInterp() ; if ( tcl_interp == NULL ) { fprintf( stderr, "Could not create interpreter!\n" ) ; return 1 ; } /* Register the commands specific to my application Tcl_CreateObjCommand( tcl_interp, "session", GppSessionCmd, (ClientData) NULL, GppDummyDestroy ) ; /* Read the configuration file with specific script code (in reality, I use a function that searches for the file and opens it! Hence I need to do more work ... If you have the file name, then use Tcl_EvalFile()!) */ infile = fopen( "scripts.conf", "r" ) ; if ( infile == NULL ) { return 1 ; } /* Now, read the whole file ... */ fseek( infile, 0L, SEEK_END ) ; filesize = ftell( infile ) ; pstr = (char *) malloc( (filesize+1) * sizeof(char) ) ; fseek( infile, 0L, SEEK_SET ) ; fread( pstr, filesize, 1, infile ) ; pstr[filesize] = '\0' ; rc = Tcl_Eval( tcl_interp, pstr ) ; if ( rc != TCL_OK ) { fprintf( stderr, "Error loading script library\n" ) ; return 1 ; } free( pstr ) ; return 0; } /* Function for encapsulating the details */ EvalScriptCommand( char * command ) { if ( Tcl_Eval( tcl_interp, command ) == TCL_OK ) { return 0 ; } else { return 1 ; } }
//compile with g++ and run using ./exec