From 0bfbf564ff8f653d2412eb196bd362c76fee4ae6 Mon Sep 17 00:00:00 2001
From: johannst <johannes.stoelp@gmail.com>
Date: Fri, 18 Sep 2020 20:08:35 +0200
Subject: added gnu make notes

---
 src/development/README.md |   1 +
 src/development/make.md   | 105 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 106 insertions(+)
 create mode 100644 src/development/make.md

(limited to 'src/development')

diff --git a/src/development/README.md b/src/development/README.md
index bda0ca3..2446271 100644
--- a/src/development/README.md
+++ b/src/development/README.md
@@ -4,4 +4,5 @@
 - [c++](./c++.md)
 - [glibc](./glibc.md)
 - [gcc](./gcc.md)
+- [make] (./make.md)
 - [ld.so](./ld.so.md)
diff --git a/src/development/make.md b/src/development/make.md
new file mode 100644
index 0000000..751b460
--- /dev/null
+++ b/src/development/make.md
@@ -0,0 +1,105 @@
+# make(1)
+
+## Anatomy of `make` rules
+```make
+target .. : prerequisite ..
+	recipe
+	..
+```
+
+- `target`: an output generated by the rule
+- `prerequisite`: an input that is used to generate the target
+- `recipe`: list of actions to generate the output from the input
+
+## Pattern rules & Automatic variables
+### Pattern rules
+A pattern rule contains the `%` char (exactly one of them) and look like this example:
+```make
+%.o : %.c
+	$(CC) -c $(CFLAGS) $(CPPFLAGS) $< -o $@
+```
+The target matches files of the pattern `%.o`, where `%` matches any none-empty
+substring and other character match just them self.
+
+The substring matched by `%` is called the `stem`.
+
+`%` in the prerequisite stands for the matched `stem` in the target.
+
+### Automatic variables
+As targets and prerequisites in pattern rules can't be spelled explicitly in
+the recipe, make provides a set of automatic variables to work with:
+- `$@`: Name of the target that triggered the rule.
+- `$<`: Name of the first prerequisite.
+- `$^`: Names of all prerequisites (without duplicates).
+- `$+`: Names of all prerequisites (with duplicates).
+- `$*`: Stem of the pattern rule.
+
+```make
+# file: Makefile
+
+all: foobar blabla
+
+foo% bla%: aaa bbb bbb
+	@echo "@ = $@"
+	@echo "< = $<"
+	@echo "^ = $^"
+	@echo "+ = $+"
+	@echo "* = $*"
+	@echo "----"
+
+aaa:
+bbb:
+```
+
+Running above `Makefile` gives:
+```test
+@ = foobar
+< = aaa
+^ = aaa bbb
++ = aaa bbb bbb
+* = bar
+----
+@ = blabla
+< = aaa
+^ = aaa bbb
++ = aaa bbb bbb
+* = bla
+----
+```
+
+## Useful functions
+
+### Substitution references
+Substitute strings matching pattern in a list.
+```make
+in  := a.o l.a c.o
+out := $(in:.o=.c)
+# => out = a.c l.a c.c
+```
+
+### `filter`
+Keep strings matching a pattern in a list.
+```make
+in  := a.a b.b c.c d.d
+out := $(filter %.b %.c, $(in))
+# => out = b.b c.c
+```
+
+### `filter-out`
+Remove strings matching a pattern from a list.
+```make
+in  := a.a b.b c.c d.d
+out := $(filter-out %.b %.c, $(in))
+# => out = a.a d.d
+```
+
+### `abspath`
+Resolve each file name as absolute path (don't resolve symlinks).
+```make
+$(abspath fname1 fname2 ..)
+
+### `realpath`
+Resolve each file name as canonical path.
+```make
+$(realpath fname1 fname2 ..)
+```
-- 
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