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How to optimize the Makefile in shell?
You’ll commonly see in Makefiles an execution of the pwd command to get the current working directory into a variable (in this case CWD): CWD = $(shell pwd) It’s this command we’ll take a look at later on when considering how to optimize an example Makefile that wastes time getting the working directory over and over again.
What does$ ( warning ) do in makefile?
The $ (warning) doesn’t change the value of CWD, but it does output a message to STDERR. From the output you can see that eight calls to the shell and which lines in the Makefile caused them. It’ll print out the line number and details of every line in Makefile that contains a $ (shell) and doesn’t contain a :=.
How to do go together in a makefile?
For example, if we ask for the value of $ (FOOBAR) it will get the value of $ (FOO) and $ (BAR) put them together with the space in between and return foo bar. Expansion through as many levels of macros as necessary is done only when the variable is used. appears to have two different values. Running it prints out:
How are macros evaluated in a makefile?
When a rule is being defined in a Makefile, macros will evaluate to their value at that point in the Makefile. Macros used in rule bodies (i.e. in the commands) have their final value: whatever value the macro had at the end of the Makefile.
How to make a makefile print the exact line?
In a real Makefile this could be a large time saver. Since it can be hard to follow through a Makefile to see everywhere a macro is used there’s a simple trick that will cause Make to print out the exact line at which a macro is expanded. If we insert $ (warning Call to shell) in the definition of CWD so that its definition is
How to make a makefile on command line?
To use this makefile, simply cd to the directory and type “ makepp ”. Makepp will attempt to build the first target in the makefile, which is my_program. (If you don’t want it to build the first target, then you have to supply a the name of the target you actually want to build on the command line.)
What is the goal of the Makefile program?
The goal of Makefiles is to compile whatever files need to be compiled, based on what files have changed. But when files in interpreted languages change, nothing needs to get recompiled. When the program runs, the most recent version of the file is used. To run these examples, you’ll need a terminal and “make” installed.
Which is the default target in the Makefile?
This makefile has a single target, called some_file. The default target is the first target, so in this case some_file will run. This file will make some_file the first time, and the second time notice it’s already made, resulting in make: ‘some_file’ is up to date.