How does 'make install' work?

fabulousUnicorn · 11-19-2021, 03:31 PM

I have a number of rather odd questions about the 'make install' command.

1) What utility does it use to install the files to their final location on the system? Does it use 'cp', 'mv, 'install' or something else?

2) What happens if it is installing a file to the system, and a that file already exists on the system?

3) What if the file already exists on the system, and that file is currently being read or written to by another program?

Thank you for any replies. I am writing a set of python scripts to help manage my packages on an LFS installation I am doing. I want a deeper understanding of the 'make install' tool to help guide my design decisions for these scripts. This is my first question on this forum, so if I have done anything incorrectly, let me know.

teckk · 11-19-2021, 04:08 PM

https://www.gnu.org/software/make/
https://www.gnu.org/software/make/manual/make.html

make install does whatever the Makefile author wants it to do.
https://superuser.com/questions/3601...ake-install-do

dugan · 11-19-2021, 05:23 PM

Quote:

Originally Posted by fabulousUnicorn

2) What happens if it is installing a file to the system, and a that file already exists on the system?

It's overwritten.

enigma9o7 · 11-19-2021, 05:44 PM

Quote:

Originally Posted by dugan

It's overwritten.

That depends on what command and switches author of Makefile made... and possibly any defaults the shell is set for on your system if no switches used in Makefile, etc...

OP is basically asking what a script does, so nobody knows without seeing a copy of the script, in this case the Makefile.

rtmistler · 11-19-2021, 06:08 PM

You should read the Makefile. Each one is unique, depending on how it was written.

See the references provided by teckk to learn about Make and Makefiles.

Regarding your specific questions, it can use cp and it can overwrite files, if there are access problems it can fail.

kermitdafrog8 · 11-19-2021, 09:50 PM

You can also do 'make install DESTDIR=/tmp'. It will create an installation of the program to say /tmp/$prefix. Like /tmp/usr/bin. Hope that makes sense.

BudiKusasi · 11-20-2021, 12:08 AM

must learn make script language which is Makefile, find line: install: as target in its syntax

also learn cp, mv, install, by follow it --help

install just cp with chmod option can be in CLI argument

shruggy · 11-20-2021, 12:56 PM

Quote:

Originally Posted by kermitdafrog8

You can also do 'make install DESTDIR=/tmp'. It will create an installation of the program to say /tmp/$prefix. Like /tmp/usr/bin.

This will only work if author of Makefile provided for DESTDIR. Not all authors do.

A common case where this will work is a Makefile generated by GNU Autotools.

But ultimately, the only way to know for sure what make install does is examining the contents of the Makefile.

kermitdafrog8 · 11-20-2021, 06:12 PM

Quote:

Originally Posted by shruggy

This will only work if author of Makefile provided for DESTDIR. Not all authors do.

A common case where this will work is a Makefile generated by GNU Autotools.

But ultimately, the only way to know for sure what make install does is examining the contents of the Makefile.

Well true. Most Makefile is generated after running configure. And yes you are correct about checking the Makefile for how it handles the install.

sundialsvcs · 11-21-2021, 06:18 PM

Let me try to step back here and provide a little "big picture background" information – before or after you begin to self-educate yourself about the "make" command.

"make" is a very-clever command whose syntax is: make [targetname]

These "targets" (including the default one, which is used if you don't specify one ...) are spelled out in a file that ... amazingly enough ... is named "Makefile"

For each "target," the Makefile says exactly what "make" must do in order to "make it." The actual sequence can become quite complicated, so I need to stop my discussion this point.

However, if you examine the contents of "Makefile", which is actually an ordinary text file, you will customarily find in it definitions for targets such as install, as well as other ones such as "uninstall" or "reinstall."

You can expect the Makefile authors to have anticipated that a file might already exist, but you should yourself make sure that an application is not in use before changing it. (Makefile authors cannot anticipate everything.)

"HTH!!"

teckk · 11-22-2021, 08:09 AM

For the OP

hellomake.c

Code:

#include <hellomake.h>

int main() 
{
  myPrintHelloMake();
  return(0);
}

hellomake.h

Code:

void myPrintHelloMake(void);

hellofunc.c

Code:

#include <stdio.h>
#include <hellomake.h>

void myPrintHelloMake(void) 
{
  printf("This is for Makefiles!!!\n");
  return;
}

You could compile that with

Code:

gcc -o hellomake hellomake.c hellofunc.c -I.

Run the executable.

Lets make a simple makefile

Code:

CC=gcc
CFLAGS=-I.
DEPS = hellomake.h

%.o: %.c $(DEPS)
	$(CC) -c -o $@ $< $(CFLAGS)
	
hellomake: hellomake.o hellofunc.o 
	$(CC) -o hellomake hellomake.o hellofunc.o

Run make in that directory. Run the executable.

Then go from there.

Example:

Code:

CC = gcc
CFLAGS = `pkg-config --cflags pangocairo sdl gl`
LIBS = `pkg-config --libs pangocairo sdl gl`

build:
	$(CC) $(CFLAGS) $(LIBS) something.c -o something

run:
	./something

clean:
	rm something

You make the Makefile or, use one of the tools that make a Makefile for you.