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Makefile basics

  • C course
  • Intermediate
  • Lesson 62/116
  • 5 min

Learn build automation with Makefile.

What is a Makefile?

A Makefile is the build recipe file that make reads. In multi-file C projects, compiling each file by hand is tiring; Makefile automates it. Each rule has a target, prerequisites and a recipe line.

Format: app: main.c utils.c (target: prerequisites), the next line starts with a TAB and holds the recipe gcc -o app main.c utils.c. Running make app builds the target. Make detects changed files; it only rebuilds what's needed. That's why it saves time in large projects.

Variables and clean

A Makefile defines variables: CC = gcc, CFLAGS = -Wall -g. In recipes use $(CC) $(CFLAGS) -o app main.c. This lets you change the compiler and flags in one place.

A common target is clean: under clean: write rm -f app *.o. Running make clean removes build products. For phony targets (clean, all) the .PHONY: clean declaration is recommended; it prevents clashes with file names. This pattern is standard across C projects.

Practice Write a Makefile

Write a Makefile: the CC = gcc variable, the app: main.c target, a TAB-led recipe $(CC) -o app main.c, the clean: target and a TAB-led rm -f app recipe. Output should be gcc -o app main.c.

Starter code

main.c
# Makefile: write app and clean targets
# CC = gcc
# app: main.c
# 	Compile app with $(CC)
# clean:
# 	Remove app

Sample solution

main.c
CC = gcc
app: main.c
	$(CC) -o app main.c
clean:
	rm -f app

Expected output

gcc -o app main.c

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 How must a Makefile recipe line start?

  • With two spaces
  • With a space
  • With a TAB Correct answer
  • With a comment

Explanation: A Makefile recipe line must start with a TAB.

2 Complete the Makefile target

Question 
app: main.c utils.c
	gcc -o ____ main.c utils.c
Answer 
app: main.c utils.c
	gcc -o app main.c utils.c

Explanation: gcc -o app main.c utils.c names the output app.

3 Match Makefile parts

Term Meaning
app: main.c Target and prerequisite
gcc ... Recipe line
CC = gcc Variable definition
clean: Phony target

All lessons in Intermediate

1 Advanced pointers

  1. Pointer to pointer
  2. Array of pointers
  3. Function pointers
  4. Function pointer parameter
  5. void pointer
  6. Summary - Advanced pointers

2 Memory management

  1. Dynamic array
  2. Resize with realloc
  3. Memory leaks
  4. Dangling pointers
  5. Allocation patterns
  6. Summary - Memory management

3 Project: Helper library

  1. Module design
  2. String helpers
  3. Number helpers
  4. Array helpers
  5. Putting it together

4 Advanced string handling

  1. Dynamic strings
  2. String concatenation
  3. String search
  4. String conversion
  5. String safety
  6. Summary - Advanced strings

5 Function pointers

  1. Function pointer definition
  2. Calling function pointers
  3. qsort
  4. Callback patterns
  5. Function pointer array
  6. Summary - Function pointers

6 Advanced structs

  1. Structs and pointers
  2. Dynamic struct
  3. Struct and function
  4. Nested structs
  5. Array of structs
  6. Summary - Advanced structs

7 Unions and enums

  1. union
  2. enum
  3. Struct and union
  4. typedef enum
  5. Bit fields
  6. Summary - Unions and enums

8 Project: Quiz app

  1. Quiz model
  2. Adding questions
  3. Running the quiz
  4. Score calculation
  5. Putting it together

9 File I/O

  1. FILE and fopen
  2. fprintf and fscanf
  3. fgets and fputs
  4. fclose
  5. fread and fwrite
  6. Summary - File I/O

10 Error handling

  1. errno
  2. perror
  3. strerror
  4. assert
  5. Error return values
  6. Summary - Error handling

11 Multi-file projects

  1. Headers and sources
  2. extern
  3. static
  4. Makefile basics
  5. Multiple modules
  6. Summary - Multi-file

12 Project: Library app

  1. Model design
  2. Library module
  3. Checking out
  4. Search and filter
  5. Putting it together

13 Dynamic data structures

  1. Linked list
  2. Adding to list
  3. Traversing list
  4. Deleting from list
  5. Stack and queue
  6. Summary - Dynamic data

14 Variable arguments

  1. stdarg.h
  2. va_start and va_end
  3. printf-like function
  4. vsnprintf
  5. Variadic patterns
  6. Summary - Variable arguments

15 Standard library

  1. stdlib.h
  2. string.h
  3. math.h
  4. time.h
  5. ctype.h
  6. Summary - Standard library

16 Command-line arguments

  1. argc and argv
  2. Argument processing
  3. getopt
  4. Argument validation
  5. Exit codes
  6. Summary - Command line

17 Debugging

  1. gdb basics
  2. Breakpoints
  3. Watch and print
  4. valgrind
  5. printf debugging
  6. Summary - Debugging

18 Advanced bitwise

  1. Bit masking
  2. Set and clear bits
  3. Bit shifting
  4. Bit hacks
  5. Pack and unpack
  6. Summary - Advanced bitwise

19 Advanced typedef

  1. typedef and struct
  2. typedef and function pointer
  3. typedef and array
  4. Opaque types
  5. typedef and enum
  6. Summary - Advanced typedef

20 Intermediate final

  1. Project design
  2. Data model
  3. Functional logic
  4. File I/O
  5. Putting it together