Fakefile Interpreter

An interpreter for a Fakefile file, which is much like a simple version of Makefile.

target: dependency.c other_dep.txt
    cat other_dep.txt | grep content
    cc -g -o target dependency.c
    ...

# this is a comment

other_dep.txt:
    echo "other dep file content" > other_dep.txt

Adapted from the way Makefiles work. Implemented a simpler subset of this functionality and, instead of passing commands to the shell to be ran, created an pipeline utilizing fork(), exec(), pipe() and dup2() in order to practice process control.

Execution Process

For running the application follow the following steps

1. Run make for creating the fake executable file
2. cd into the test directory
3. For running the contents within Fakefile use command ../fake
4. (Optional) If you wish to run any other than Fakefile use the -f flag: ../fake -f Newfile

Implementation

First Steps

1. Automatically open a file named Fakefile when the program (named fake) is executed.
2. Parse this file line by line looking for:
   • Comments to ignore (any line that starts with a #)
   • Rule targets and prerequisites (any line that doesn't start with a # or \t)
   • "Recipe" actions (lines under rule targets and prerequisites that begin with \t)
3. Complete "recipes" are separated by a blank line.
4. Annoyingly throws errors if the file is formatted incorrectly.
5. There are no "implicit rules", everything must be included in the Fakefile.

Parsing Recipes

1. For each recipe, check if the target is missing in the current directory or if any dependencies are more recent than the file named target
   • If this is true, perform each action under the target and prerequisites
   • If false, the target is up to date, nothing needs to be done
2. Because some targets can depend on other targets that come later in the file, the entire Fakefile must be read first and a dependency tree created. This data structure is up to you (but a stack should be sufficient ...)

Final Steps

1. Execute each command in the recipe using fork() and exec() family of functions.
2. Parse the command line, looking for | (pipe) characters to use the pipe() function, or </> (input/output redirection) to redirect a file as input or output, respectively.
3. If a recipe fails (exit status was non-zero), then stops executing recipes.
4. When executed, if the user provides a target name, runs that target instead of the first (default) target.

Testing

1. Compared the behavior with make tool by using the -f flag: make -f Fakefile