TAGS: MakeFile
=== QUESTION ===
Please write a GNU Makefile, which uses the command `cmm print -f db/<fname> -a >out/gpu_plan.md` and `python convert.py out/gpu_plan.md` if source file is changing, to create `out/gpu_plan.html`.
==== ANSWER ====
Here's a GNU Makefile that performs the required operations:

```makefile
# Variables to define the source and output directories
SRC_DIR = db
OUT_DIR = out

# List of source files without extension
SOURCES = 0014 0022 0013 0001 0016 0017 0018 0023 0019 0002 0025

# Add directory and extension to the source filenames
SRC_FILES = $(SOURCES:%=$(SRC_DIR)/%.txt)

# Add directory and .md extension to the markdown filenames
MD_FILES = $(SOURCES:%=$(OUT_DIR)/%.md)

# Add .html extension for the HTML filenames
HTML_FILES = $(MD_FILES:.md=.html)

# Default target
all: Makefile convert.py $(HTML_FILES) $(OUT_DIR)/learning.html

Makefile: $(SRC_DIR)/0026.txt
        cmm print -f $< -S | sed "s/    `printf '    /\t/g'`" >$@

convert.py: $(SRC_DIR)/0003.txt Makefile
        cmm print -f $< -S >$@

# Rule to create a markdown file from a source file
$(OUT_DIR)/%.md: $(SRC_DIR)/%.txt
        cmm print -f $< -a > $@

# Rule to create an HTML file from a markdown file
$(OUT_DIR)/%.html: $(OUT_DIR)/%.md convert.py
        python convert.py $<

$(OUT_DIR)/learning.html: $(SRC_DIR)/0015.txt $(SRC_FILES) Makefile
        cmm print -f $< -S | \
        awk "/LINKS_LINE/ { \
            split(\"$(SOURCES)\", sources, \" \"); \
            for (i = 1; i <= length(sources); i++) { \
                \"awk '/^# /{ sub(/^# /, \\\"\\\"); print \$0; }' db/\" sources[i] \".txt\" | getline NAME; \
                print \"        <li><a href=\\\"\" sources[i] \".html\\\">\" NAME \"</a></li>\"; \
            } \
        } 1" > $@

# Target to clean the output directory
clean:
        rm -f $(OUT_DIR)/*

.PHONY: all clean
```

In this `Makefile`:

1. `SOURCES` is a list of all source files (without their file extensions). You can add or remove file names from this list as needed.
2. The `SRC_FILES`, `MD_FILES`, and `HTML_FILES` variables generate the full filenames with directory and extension based on the `SOURCES` list.
3. The `$(OUT_DIR)/%.md: $(SRC_DIR)/%.txt` and `$(OUT_DIR)/%.html: $(OUT_DIR)/%.md` rules use pattern-matching to create the appropriate `.md` or `.html` file for each source file.
4. The `all` target now depends on `$(HTML_FILES)`, which means it will generate an HTML file for each source file listed in `SOURCES`.

The `%.txt` and `%.md` are pattern matching rules that match any file with a `.txt` or `.md` extension respectively. `$<` refers to the first prerequisite (i.e., the source file), and `$@` refers to the target of the rule.

Generate the `Makefile` with this command: `cmm print -f db/0026.txt -S | sed $'s/        /\t/g' >Makefile`

To run this `Makefile`, you can still use `make` command in the terminal, and `make clean` to clean up the output directory.