Make

Variables Commands

Make variables control build behavior. Master assignment operators and automatic variables for flexible, maintainable Makefiles.

9 commands

Pro Tips

Use := for simple expansion to avoid recursive evaluation issues.

Use ?= to set defaults that can be overridden by environment.

Common Mistakes

= (recursive) variables expand each use - can cause infinite loops.

Commands

Simple variable

$ CC := gcc

Immediate assignment (expanded once).

Recursive variable

$ CFLAGS = $(OPTS) -Wall

Deferred assignment (expanded each use).

Append to variable

$ CFLAGS += -O2

Add to existing value.

Conditional set

$ CC ?= gcc

Set only if not already defined.

Environment export

$ export PATH := $(PATH):./bin

Export variable to shell.

Automatic $@

$ $(CC) -o $@ $^

$@ = target name.

Automatic $<

$ $(CC) -c $<

$< = first prerequisite.

Automatic $^

$ $(CC) -o $@ $^

$^ = all prerequisites.

Pattern stem

$ %.o: %.c $(CC) -c $< -o $@

$* = matched pattern stem.

Make

Variables Commands

Make variables control build behavior. Master assignment operators and automatic variables for flexible, maintainable Makefiles.

9 commands

Pro Tips

Use := for simple expansion to avoid recursive evaluation issues.

Use ?= to set defaults that can be overridden by environment.

Common Mistakes

= (recursive) variables expand each use - can cause infinite loops.

Commands

Simple variable

$ CC := gcc

Immediate assignment (expanded once).

Recursive variable

$ CFLAGS = $(OPTS) -Wall

Deferred assignment (expanded each use).

Append to variable

$ CFLAGS += -O2

Add to existing value.

Conditional set

$ CC ?= gcc

Set only if not already defined.

Environment export

$ export PATH := $(PATH):./bin

Export variable to shell.

Automatic $@

$ $(CC) -o $@ $^

$@ = target name.

Automatic $<

$ $(CC) -c $<

$< = first prerequisite.

Automatic $^

$ $(CC) -o $@ $^

$^ = all prerequisites.

Pattern stem

$ %.o: %.c $(CC) -c $< -o $@

$* = matched pattern stem.