make - maintain program groups

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SYNOPSIS

DESCRIPTION

The make utility updates a target if it depends on prerequisite files that have been modified since the target was last modified, or if the target does not exist.

A makefile contains a sequence of entries that specify dependencies. The first line of an entry is a blank-separated list of targets, then a colon, then a list of prerequisite files. Text following a semicolon, and all following lines that begin with a tab, are shell commands to be executed to update the target. If a name appears on the left of more than one `colon' line, then it depends on all of the names on the right of the colon on those lines, but only one command sequence may be specified for it. If a name appears on a line with a double colon :: then the command sequence following that line is performed only if the name is out of date with respect to the names to the right of the double colon, and is not affected by other double colon lines on which that name may appear.

Two special forms of a name are recognized. A name like a(b) means the file named b stored in the archive named a. A name like a((b)) means the file stored in archive a containing the entry point b.

Sharp and newline surround comments.

The following makefile says that `pgm' depends on two files `a.o' and `b.o', and that they in turn depend on `.c' files and a common file `incl'.

pgm: a.o b.o
cc a.o b.o -lm -o pgm


a.o: incl a.c
cc -c a.c

b.o: incl b.c
cc -c b.c

Makefile entries of the form

string1 = string2

are macro definitions. Subsequent appearances of $(string1) or ${string1} are replaced by string2. If string1 is a single character, the parentheses or braces are optional.

The make utility infers prerequisites for files for which makefile gives no construction commands. For example, a `.c' file may be inferred as prerequisite for a `.o' file and be compiled to produce the `.o' file. Thus the preceding example can be done more briefly:

pgm: a.o b.o
cc a.o b.o -lm -o pgm


a.o b.o: incl

Prerequisites are inferred according to selected suffixes listed as the `prerequisites' for the special name `.SUFFIXES'; multiple lists accumulate; an empty list clears what came before. Order is significant; the first possible name for which both a file and a rule as described in the next paragraph exist is inferred. The default list is

.SUFFIXES: .out .o .c .e .r .f .y .l .s .p

The rule to create a file with suffix s2 that depends on a similarly named file with suffix s1 is specified as an entry for the `target' s1s2. In such an entry, the special macro $* stands for the target name with suffix deleted, $@ for the full target name, $< for the name of the file that the target depends upon, and $? for the list of prerequisites that are out of date. For example, a rule for making optimized `.o' files from `.c' files is

.c.o: ; cc -c -O -o $@ $*.c

Certain macros are used by the default inference rules to communicate optional arguments to any resulting compilations. In particular, `CFLAGS' is used for cc.1 options, and `LFLAGS' and `YFLAGS' for lex and yacc.1 options. In addition, the macro `MFLAGS' is filled in with the initial command line options supplied to make. This simplifies maintaining a hierarchy of makefiles as one may then invoke make on makefiles in subdirectories and pass along useful options such as -k, explained below.

Another special macro is `VPATH'. The `VPATH' macro should be set to a list of directories separated by colons. When make searches for a file as a result of a dependency relation, it will first search the current directory and then each of the directories on the `VPATH' list. If the file is found, the actual path to the file will be used, rather than just the filename. If `VPATH' is not defined, then only the current directory is searched.

One use for `VPATH' is when one has several programs that compile from the same source. The source can be kept in one directory and each set of object files (along with a separate makefile) would be in a separate subdirectory. The `VPATH' macro would point to the source directory in this case.

Command lines are executed one at a time, each by its own shell. A line is printed when it is executed unless the special target `.SILENT' is in makefile, or the first character of the command is `@'.

Commands returning nonzero status (see intro.1 cause make to terminate unless the special target `.IGNORE' is in makefile or the command begins with <tab><hyphen>.

Interrupt and quit cause the target to be deleted unless the target is a directory or depends on the special name `.PRECIOUS'.

Other options:

-d

Debug mode. Print detailed information on files and times examined.

-i

Equivalent to the special entry `.IGNORE:'.

-k

When a command returns nonzero status, abandon work on the current entry, but continue on branches that do not depend on the current entry.

-n

Trace and print, but do not execute the commands needed to update the targets.

-p

Print the complete set of macro definitions and target descriptions.

-q

Question. The make command returns a zero or non-zero status code depending upon whether the target file is or is not up to date, without executing any commands on the action lines.

-t

Touch, i.e. update the modified date of targets, without executing any commands on the action lines.

-r

Equivalent to an initial special entry `.SUFFIXES:' with no list.

-s

Equivalent to the special entry `.SILENT:'.

FILES

SEE ALSO

BUGS

Commands that are directly executed by the shell, notably cd.1 are ineffectual across newlines in make.

`VPATH' is intended to act like the System V `VPATH' support, but there is no guarantee that it functions identically.

Created by unroff & hp-tools. © somebody (See intro for details). All Rights Reserved. Last modified 11/5/97