make(1)

NAME

make − maintain program groups

SYNTAX

make [−f makefile] [option...] file...

DESCRIPTION

The make command executes commands in makefile to update one or more target names. The name is typically a program. If no −f option is present, ‘makefile’ and ‘Makefile’ are tried in order. If makefile is ‘−’, the standard input is taken. More than one −f option may appear

The make command 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.

The 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appears on a line with a double colon :: then the command sequence following that line is performed only if the name is out of date with respect to the names to the right of the double colon, and is not affected by other double colon lines on which that name may appear.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.

Pound (#) and new line 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 command 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 complete list of prerequisites, 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() options, ‘FFLAGS’ for f77() options, ‘PFLAGS’ for pc1 options, and ‘LFLAGS’ and ‘YFLAGS’ for lex and yacc() 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.

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 cause make to terminate unless the special target ‘.IGNORE’ is in makefile or the command begins with <tab><hyphen>. For further information, see intro()

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

OPTIONS

−fUses specified file as input. Defaults are makefile and Makefile, respectively, in your current directory.

−iEquals an .IGNORE: entry.

−k
Stops processing current entry on nonzero return, but continues with other branches that do not depend on that entry.

−nTraces, prints, but does not update programs.

−rEquals an initial .SUFFIXES: entry with no list.

−sEquals a .SILENT: entry.

−tTouches (updates) modification date of each target program only.

RESTRICTIONS

Some commands return nonzero status inappropriately. Use −i to overcome the difficulty.
Commands that are directly executed by the shell, notably cd(1), are ineffectual across new lines in make.

FILES

makefile, Makefile

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