make - maintain program groups
make [ -f makefile ] [ option ] ... file ...
Make executes commands in makefile to update one or more target names. 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
Make 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.
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.
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) are replaced by string2. If
string1 is a single character, the parentheses are optional.
Make 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
The rule to create a file with suffix s2 that depends on a similarly named file with suf-
fix 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 for the list of prerequisites that are out
of date.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 and f77(1) options,
`LFLAGS' and `YFLAGS' for lex and yacc(1) options.
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 spe-
cial target `.IGNORE' is in makefile or the command begins with <tab><hyphen>.
Interrupt and quit cause the target to be deleted unless the target depends on the special
-i Equivalent to the special entry `.IGNORE:'.
-k When a command returns nonzero status, abandon work on the current entry, but con-
tinue 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.
-t Touch, i.e. update the modified date of targets, without executing any commands.
-r Equivalent to an initial special entry `.SUFFIXES:' with no list.
-s Equivalent to the special entry `.SILENT:'.
S. I. Feldman Make - A Program for Maintaining Computer Programs
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
newlines in make.