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Welcome to the CJIT Tutorial

CJIT is a versatile C interpreter based on TinyCC, designed to compile C code in-memory and execute it live. This manual serves as a guide to the full potential of CJIT, empowering you to efficiently develop and test C programs in real-time.

This tutorial will guide you through practical usage examples, helping you to swiftly integrate CJIT into your workflow. 📚🔧

Download CJIT

If you have already downloaded the CJIT executable for your running system them you can skip this section.

If you like to download it by hand, go to the CJIT release page.

If you prefer to cut & paste a terminal script, pick one below for your running system:

Invoke-WebRequest -OutFile "cjit.exe" -Uri "https://github.com/dyne/cjit/releases/latest/download/cjit.exe"

curl -sLo cjit https://github.com/dyne/cjit/releases/latest/download/cjit-$(uname)-$(uname -m)
chmod +x cjit

source /etc/os-release
curl -sLo cjit "https://github.com/dyne/cjit/releases/latest/download/cjit-$(uname -m)-${NAME,,}-${VERSION_ID}"
chmod +x cjit

Info

All Windows examples are made for PowerShell, on WSL then pick GNU/Linux.

Hello World!

This classic example will make you create a hello.c file and execute it with CJIT to print the string "Hello World!" in the terminal.

Create hello.c by pasting these lines in the terminal:

@"
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char **argv) {
  fprintf(stderr,"Hello, World!\n");
  exit(0);
}
"@| Out-File -FilePath "hello.c" -Encoding ASCII

cat << EOF > hello.c
#!/usr/bin/env cjit
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char **argv) {
  fprintf(stderr,"Hello, World!\n");
  exit(0);
}
EOF

cat << EOF > hello.c
#!/usr/bin/env cjit
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char **argv) {
  fprintf(stderr,"Hello, World!\n");
  exit(0);
}
EOF

Finally execute hello.c with CJIT:

.\cjit.exe .\hello.c

./cjit hello.c

./cjit hello.c

As a result you will see CJIT starting and printing "Hello World!"

CJIT v0.16.2 by Dyne.org
Hello World!

You can play with hello.c, change what you want and run it again!

Flying Donuts

This example will print an animated donut on the terminal!

Create the donut.c file using the artful code below:

@"
             i,j,k,x,y,o,N;
         main(){float z[1760],a
      #define R(t,x,y) f=x;x-=t*y\
   ;y+=t*f;f=(3-x*x-y*y)/2;x*=f;y*=f;
   =0,e=1,c=1,d=0,f,g,h,G,H,A,t,D;char
 b[1760];for(;;){memset(b,32,1760);g=0,
h=1;memset(z,0,7040);for(j=0;j<90;j++){
G=0,H=1;for(i=0;i<314;i++){A=h+2,D=1/(G*
A*a+g*e+5);t=G*A        *e-g*a;x=40+30*D
*(H*A*d-t*c);y=          12+15*D*(H*A*c+
t*d);o=x+80*y;N          =8*((g*a-G*h*e)
*d-G*h*a-g*e-H*h        *c);if(22>y&&y>
 0&&x>0&&80>x&&D>z[o]){z[o]=D;b[o]=(N>0
  ?N:0)[".,-~:;=!*#$@"];}R(.02,H,G);}R(
  .07,h,g);}for(k=0;1761>k;k++)putchar
   (k%80?b[k]:10);R(.04,e,a);R(.02,d,
     c);usleep(15000);printf('\n'+(
        " donut.c! \x1b[23A"));}}
          /*no math lib needed
             .@a1k0n 2021.*/
"@| Out-File -FilePath "donut.c" -Encoding ASCII

cat << EOF > donut.c
             i,j,k,x,y,o,N;
         main(){float z[1760],a
      #define R(t,x,y) f=x;x-=t*y\
   ;y+=t*f;f=(3-x*x-y*y)/2;x*=f;y*=f;
   =0,e=1,c=1,d=0,f,g,h,G,H,A,t,D;char
 b[1760];for(;;){memset(b,32,1760);g=0,
h=1;memset(z,0,7040);for(j=0;j<90;j++){
G=0,H=1;for(i=0;i<314;i++){A=h+2,D=1/(G*
A*a+g*e+5);t=G*A        *e-g*a;x=40+30*D
*(H*A*d-t*c);y=          12+15*D*(H*A*c+
t*d);o=x+80*y;N          =8*((g*a-G*h*e)
*d-G*h*a-g*e-H*h        *c);if(22>y&&y>
 0&&x>0&&80>x&&D>z[o]){z[o]=D;b[o]=(N>0
  ?N:0)[".,-~:;=!*#$@"];}R(.02,H,G);}R(
  .07,h,g);}for(k=0;1761>k;k++)putchar
   (k%80?b[k]:10);R(.04,e,a);R(.02,d,
     c);usleep(15000);printf('\n'+(
        " donut.c! \x1b[23A"));}}
          /*no math lib needed
             .@a1k0n 2021.*/
EOF

cat << EOF > donut.c
             i,j,k,x,y,o,N;
         main(){float z[1760],a
      #define R(t,x,y) f=x;x-=t*y\
   ;y+=t*f;f=(3-x*x-y*y)/2;x*=f;y*=f;
   =0,e=1,c=1,d=0,f,g,h,G,H,A,t,D;char
 b[1760];for(;;){memset(b,32,1760);g=0,
h=1;memset(z,0,7040);for(j=0;j<90;j++){
G=0,H=1;for(i=0;i<314;i++){A=h+2,D=1/(G*
A*a+g*e+5);t=G*A        *e-g*a;x=40+30*D
*(H*A*d-t*c);y=          12+15*D*(H*A*c+
t*d);o=x+80*y;N          =8*((g*a-G*h*e)
*d-G*h*a-g*e-H*h        *c);if(22>y&&y>
 0&&x>0&&80>x&&D>z[o]){z[o]=D;b[o]=(N>0
  ?N:0)[".,-~:;=!*#$@"];}R(.02,H,G);}R(
  .07,h,g);}for(k=0;1761>k;k++)putchar
   (k%80?b[k]:10);R(.04,e,a);R(.02,d,
     c);usleep(15000);printf('\n'+(
        " donut.c! \x1b[23A"));}}
          /*no math lib needed
             .@a1k0n 2021.*/
EOF

Then make the donut fly with CJIT!

.\cjit.exe .\donut.c

./cjit donut.c

./cjit donut.c

Warning

With this example and other programs, just hit CTRL+C to quit.

The state of affairs in CJIT is well demonstrated by this example: right now the terminal is much slower on windows (rightmost donut).

Two flying donuts, one running on GNU/Linux to the left and one on MS/Windows to the right

Game of Life

Another fascinating example is the "Game of Life," a cellular automaton devised by the British mathematician John Horton Conway in 1970.

Our life.c example is part of the cjit-demo.tar.gz package you should download to enjoy this and other demos in this tutorial. Download, extract and copy the cjit executable inside the cjit-demo folder. Below are quick sequence of commands to do that:

Invoke-WebRequest -OutFile "life.c" -Uri "https://github.com/dyne/cjit/raw/refs/heads/main/examples/life.c"

curl -sLo life.c https://github.com/dyne/cjit/raw/refs/heads/main/examples/life.c

curl -sLo life.c https://github.com/dyne/cjit/raw/refs/heads/main/examples/life.c

Then execute the life.c source file passing it as argument to cjit, the same way it was done for the flying donut.

.\cjit.exe life.c

./cjit life.c

./cjit life.c

Have a look around the life.c file with your favorite text editor and feel free to change things and see what happens.

Game of Life in ASCII animation

⏩ Next: graphics with CJIT

Go to the next chapter of this tutorial.