How make a file

Second, if you are only making changes to one. So, it's time to see what we can do with a makefile. If you put this rule into a file called Makefile or makefile and then type make on the command line it will execute the compile command as you have written it in the makefile.

Note that make with no arguments executes the first rule in the file. Furthermore, by putting the list of files on which the command depends on the first line after the : , make knows that the rule hellomake needs to be executed if any of those files change. Immediately, you have solved problem 1 and can avoid using the up arrow repeatedly, looking for your last compile command. However, the system is still not being efficient in terms of compiling only the latest changes.

One very important thing to note is that there is a tab before the gcc command in the makefile. There must be a tab at the beginning of any command, and make will not be happy if it's not there. It turns out these are special constants that communicate to make how we want to compile the files hellomake. By putting the object files--hellomake. Using this form of makefile is sufficient for most small scale projects.

However, there is one thing missing: dependency on the include files. Here's a list of implicit rules:. Let's see how we can now build a C program without ever explicitly telling Make how to do the compililation:. Static pattern rules are another way to write less in a Makefile, but I'd say are more useful and a bit less "magic".

Here's their syntax:. Whatever was matched is called the stem. The stem is then substituted into the prereq-pattern , to generate the target's prereqs. A typical use case is to compile. Here's the manual way :. While I introduce functions later on, I'll foreshadow what you can do with them. The filter function can be used in Static pattern rules to match the correct files. In this example, I made up the.

Double-Colon Rules are rarely used, but allow multiple rules to be defined for the same target. If these were single colons, a warning would be printed and only the second set of commands would run.

Add an before a command to stop it from being printed You can also run make with -s to add an before each line. Add -k when running make to continue running even in the face of errors.

Helpful if you want to see all the errors of Make at once. Add a - before a command to suppress the error Add -i to make to have this happen for every command. The export directive takes a variable and makes it accessible to sub-make commands. In this example, cooly is exported such that the makefile in subdir can use it. Note: export has the same syntax as sh, but they aren't related although similar in function. There's a nice list of options that can be run from make. Check out --dry-run , --touch , --old-file.

You can have multiple targets to make, i. Recursive definitions will give an infinite loop error. Spaces at the end of a line are not stripped, but those at the start are. String Substitution is also a really common and useful way to modify variables. Also check out Text Functions and Filename Functions. You can override variables that come from the command line by using override. It has nothing to do with being a function.

Note here that it's a bit different than having a semi-colon between commands, because each is run in a separate shell, as expected. Run this example with make -i to see it print out the echo statement. Let's explore it line by line:. In this case, all files with the. In this case, if SRCS has values 'foo. Let's look at an example to understand this rule. Below is the rule in its expanded form:. Every prerequisite in the previous rule is considered a target for this rule.

Below is the rewrite of the above makefile, assuming it is placed in the directory having a single file foo. For more on makefiles, refer to the GNU Make manual , which offers a complete reference and examples. You can also read our Introduction to GNU Autotools to learn how to automate the generation of a makefile for your coding project.

What is a Makefile and how does it work? Run and compile your programs more efficiently with this handy automation tool. Image by :.

Get the highlights in your inbox every week. Basic examples Let's start by printing the classic "Hello World" on the terminal. More Linux resources. Our latest Linux articles.

Usage: make compile all binary make clean remove ALL binaries and objects. Topics Linux. About the author. He also likes to explore Swift Object Storage in his spare time. More about me. Recommended reading Run containers on Linux without sudo in Podman.

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Kiko Fernandez-Reyes on 22 Aug Permalink. Hi, Thanks for this tutorial.