Makefile Mystery

Blog post edited by Anonymous - "Migration of unmigrated content due to installation of a new plugin"

I was working with a makfile the other day and I came across a "feature" that I was not aware of. When running my makefile I saw the following lines appear:

cat build.sh >build
chmod a+x build

I could not find any part of the makefile that used either the cat or the chmod command yet it seemed to work. Upon further testing I discovered that Make will automatically convert a shell script to an executable. For example, consider the following makefile

"Makefile"

all:    demo

demo:   test
    ./test

clean:
    rm test

This code seems streatforward but there is no rule to build test and my clean removes test. However, the script works fine if I include the following in the same directory:

"test.sh"

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#!/bin/bash
#
echo "This is a test!!!!, Hello world"

Now when I run make, I get the following output:

>make
cat test.sh >test
chmod a+x test
./test
This is a test!!!!, Hello world

This is a really neat feature but it threw me for a loop.

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Blogpost migrated from ICER Wiki using custom python script. Comment on errors below.