make: Recipe Syntax
5.1 Recipe Syntax
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Makefiles have the unusual property that there are really two distinct
syntaxes in one file. Most of the makefile uses 'make' syntax (
Writing Makefiles Makefiles.). However, recipes are meant to be
interpreted by the shell and so they are written using shell syntax.
The 'make' program does not try to understand shell syntax: it performs
only a very few specific translations on the content of the recipe
before handing it to the shell.
Each line in the recipe must start with a tab (or the first character
in the value of the '.RECIPEPREFIX' variable; Special
Variables), except that the first recipe line may be attached to the
target-and-prerequisites line with a semicolon in between. _Any_ line
in the makefile that begins with a tab and appears in a "rule context"
(that is, after a rule has been started until another rule or variable
definition) will be considered part of a recipe for that rule. Blank
lines and lines of just comments may appear among the recipe lines; they
are ignored.
Some consequences of these rules include:
* A blank line that begins with a tab is not blank: it's an empty
recipe (Empty Recipes).
* A comment in a recipe is not a 'make' comment; it will be passed to
the shell as-is. Whether the shell treats it as a comment or not
depends on your shell.
* A variable definition in a "rule context" which is indented by a
tab as the first character on the line, will be considered part of
a recipe, not a 'make' variable definition, and passed to the
shell.
* A conditional expression ('ifdef', 'ifeq', etc. Syntax of
Conditionals Conditional Syntax.) in a "rule context" which is
indented by a tab as the first character on the line, will be
considered part of a recipe and be passed to the shell.
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make: Recipes
make: Recipes
make: Echoing