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Run a Tcl script from an encoded file
Using Tcl from C example from a Well House Consultants training course
More on Using Tcl from C [link]

This example is described in the following article(s):
   • Storing Tcl source code encoded, and running via your own C program - [link]

Source code: secret.c Module: T243
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <tcl.h>

/* Run a piece of secured Tcl from a file
*/


int main(int argc, char ** argv) {

        FILE * infile;
        char line[2049];
        char * info = NULL;

        Tcl_Interp *myinterp;

        int datalength = 0;
        int llen;
        int status;

        int k,j;
        char holder;

/* Read the encoded Tcl from the file into a char string */

        infile = fopen(argv[1],"r");

        while (fgets(line,2048,infile)) {

        // Allocate memory for pointer to line just added
                llen = strlen(line);
                info = realloc(info,(datalength + llen + 1) * sizeof(char *));
                strcpy(info+datalength,line);
                datalength += llen;

        }

        /* printf("%s",info); */

/* Interpret that char string to a real internal Tcl string */

        for (k=0; k<datalength; k+=2) {
                holder = *(info+k);
                *(info+k) = *(info+k+1);
                *(info+k+1) = holder;
        }

/* Go run it! */

        myinterp = Tcl_CreateInterp();
        status = Tcl_Eval(myinterp,info);

        printf("Phew!\n");

}

/* --------------------- Here's how we build and run that --------

munchkin:ta grahamellis$ gcc -o secret secret.c -ltcl -ldl -lm
munchkin:ta grahamellis$ ./secret mash
number of carriages? 4
number of seats per carriage? 3
That train can take 11 people
That train can take 8 cows
3
Phew!
munchkin:ta

We encoded the file like this: --------------------------------

munchkin:ta dd if=seats of=mash conv=swab
munchkin:ta

==================================================================

The file used before it was mashed looks like this:

==================================================================

proc askuser {prompt} {
        global rz
        puts -nonewline "$prompt? "
        flush stdout
        set rz [gets stdin]
        return $rz
        }

proc loader {cars seats {overload 1.4}} {
        set capacity [expr int($cars * ($seats - 1) * $overload + 0.5)]
        return $capacity
        }

# hide clever stuff in "proc"s
# ----------- here comes the main program -------------

set rz "Loading program for Second Little Western"

set nc [askuser "number of carriages"]
set spc [askuser "number of seats per carriage"]

set capacity [loader $nc $spc]
puts [format "That train can take %d people" $capacity]

set capacity [loader $nc $spc 1.0]
puts [format "That train can take %d cows" $capacity]

puts $rz

==================================================================

And here is the mashed Tcl file ;-)

==================================================================

p
or csaukes rp{orpm}t{
lgbolar
zp tu sn-noweilen" p$orpm?t"
lfsu htsodtu
es tzr[ egsts dtni
]r teru nr$
z}

rpco oldare{ acsrs aest{ voreolda1 4.}}{
es tacapicyt[ xerpi tn$(acsr* ( s$aest- 1 ) *o$evlrao d +.0)5
]r teru nc$pacati
y}

 #ihedc elev rtsfu fni" rpcos"#
- ----------h re eocem sht eamnip orrgma- ------------

es tzr" oLdani grpgoar mof reSocdnL tilt eeWtsre"n
s
ten ca[kssure" unbmreo facrraieg"s
]es tps ca[kssure" unbmreo festa sep racrraieg]"

es tacapicyt[ oldare$ cn$ ps]cp
tu sf[roam tT"ah trtia nac natek% deppoel "c$pacati]y

es tacapicyt[ oldare$ cn$ ps c.1]0p
tu sf[roam tT"ah trtia nac natek% docsw "c$pacati]y

upst$ zr

*/

Learn about this subject
This module and example are covered on the following public courses:
 * Learning to program in Tcl
 * Tcl Programming
 * Tcl Programming
Also available on on site courses for larger groups

Books covering this topic
Yes. We have over 700 books in our library. Books covering Tcl, Tk and Expect are listed here and when you've selected a relevant book we'll link you on to Amazon to order.

Other Examples
This example comes from our "Using Tcl from C" training module. You'll find a description of the topic and some other closely related examples on the "Using Tcl from C" module index page.

Full description of the source code
You can learn more about this example on the training courses listed on this page, on which you'll be given a full set of training notes.

Many other training modules are available for download (for limited use) from our download centre under an Open Training Notes License.

Other resources
• Our Solutions centre provides a number of longer technical articles.
• Our Opentalk forum archive provides a question and answer centre.
The Horse's mouth provides a daily tip or thought.
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• And there's a global index here.

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