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

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