Shulou(Shulou.com)06/02 Report--

8. Conditional judgment statement 8.1. rule of grammar

Conditional judgment statements are supported in Makefile, which can directly compare the values and constant values of two different variables.

Note: conditional judgment statements can only be used to control the statements actually executed by make, not the execution of commands in rules.

Conditional interpretation grammar description:

Conditional judgment keyword:

Example:

.PHONY: testvar1: = Avar2: = $(var1) var3: = test: ifeq ($(var1), $(var2)) @ echo "var1 = = var2" else @ echo "var1! = var2" endif ifneq ($(var2) ) @ echo "var2 is NOT empty" else @ echo "var2 is empty" endif ifdef var2 @ echo "var2 is NOT empty" else @ echo "var2 is empty" endif ifndef var3 @ echo "var3 is empty" else @ echo "var3 is NOT empty" endif

Output result:

8.2. Engineering experience

1. Conditional judgment statements can be preceded by spaces, but cannot have Tab characters ('\ t')

two。 Do not use automatic variables ($@ $^ @) in conditional statements

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