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Chapter 19 The make Utility
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Instructions in the description file are interpreted as single lines.
If an instruction must span more than one input line, use a backslash
(\) at the end of the line so that the next line is considered as a
continuation.
The description file may contain any of the following types of lines:
-
blank lines
-
Blank lines are ignored.
-
comment lines
-
A pound sign (#) can be used at the beginning of a line or anywhere
in the middle.
make
ignores everything after the #.
-
dependency lines
-
Depending on one or more targets, certain commands that follow will be
executed. Possible formats include:
targets
:
prerequisites
targets
::
prerequisites
In the first form, subsequent commands are executed if the prerequisites are met.
The second form is a variant that lets you specify the same targets on more
than one dependency line. In both forms, if no prerequisites are supplied,
then subsequent commands are
always
executed (whenever any of
the targets are specified). No tab should precede any
targets
.
(At the end of a dependency line, you can specify a command,
preceded by a semicolon; however, commands are typically entered
on their own lines, preceded by a tab.)
-
suffix rules
-
These specify that files ending with the first suffix can be prerequisites for
files ending with the second suffix (assuming the root filenames are the
same). Either of these formats can be used:
.
suffix
.
suffix
:
.
suffix
:
The second form means that the root filename depends on the filename with the
corresponding suffix.
Commands are grouped below the dependency line and
are typed on lines that begin with a tab.
If a command is preceded by a hyphen (-),
make
ignores
any error returned. If a command is preceded by an at-sign (@),
the command line won't echo on the display (unless
make
is called
with
-n
).
-
macro definitions
-
These have the following form:
name
=
string
Blank space is optional around the =.
-
include statements
-
Similar to the C include directive, these have the form:
include
file
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