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.Dd October 23, 2015
.Dt MKDEP 1
.Os
.Sh NAME
.Nm mkdep
.Nd construct Makefile dependency list
.Sh SYNOPSIS
.Nm
.Op Fl ap
.Op Fl f Ar file
.Op Ar flags
.Ar
.Sh DESCRIPTION
The
.Nm
utility takes a set of flags for the C compiler and a list
of C source files as arguments and constructs a set of include
file dependencies which are written into the file ``.depend''.
An example of its use in a Makefile might be:
.Bd -literal -offset indent
CFLAGS= -O -I../include
SRCS= file1.c file2.c

depend:
	mkdep ${CFLAGS} ${SRCS}
.Ed
.Pp
where the macro SRCS is the list of C source files and the macro
CFLAGS is the list of flags for the C compiler.
.Pp
The user has the ability to change the preprocessor and preprocessor options
used.
For instance, to use
.Sy cc
as the preprocessor and to ignore system
headers, one would use
.Bd -literal -offset indent
depend:
	env MKDEP_CPP="cc -E" MKDEP_CPP_OPTS=-MM mkdep \\
		${CFLAGS} ${SRCS}
.Ed
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl a
Append to the output file,
so that multiple
.Nm Ns 's
may be run from a single Makefile.
.It Fl f
Write the include file dependencies to
.Ar file ,
instead of the default ``.depend''.
.It Fl p
Cause
.Nm
to produce dependencies of the form:
.Bd -literal -offset indent
program: program.c
.Ed
.Pp
so that subsequent makes will produce
.Ar program
directly from its C module rather than using an intermediate
.Pa \&.o
module.
This is useful for programs whose source is contained in a single
module.
.El
.Sh ENVIRONMENT
.Bl -tag -width MKDEP_CPP_OPTS
.It Ev CC
Specifies the C compiler to use.
The specified compiler is expected to have
options consistent with the GNU C compiler.
The default is
.Sy cc .
.It Ev MKDEP_CPP
Specifies the preprocessor to use.
The default is "${CC} -E".
.It Ev MKDEP_CPP_OPTS
Specifies the non-CFLAGS options for the preprocessor.
The default is
"-M".
.El
.Sh FILES
.Bl -tag -width .depend -compact
.It Pa .depend
File containing list of dependencies.
.El
.Sh SEE ALSO
.Xr cc 1 ,
.Xr cpp 1 ,
.Xr make 1
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.3 Tahoe .