make - Unix, Linux Command

NAME

make - utility for building and maintaining groups of programs.

SYNOPSIS

make [ -f makefile ] [ options ] ... [ targets ] ...

DESCRIPTION

make The purpose of the make utility is to determine automatically which pieces of a large program need to be recompiled, and issue the commands to recompile them. you can use make with any programming language whose compiler can be run with a shell command. In fact, make is not limited to programs. You can use it to describe any task where some files must be updated automatically from others whenever the others change.
To prepare to use make, you must write a file called the makefile that describes the relationships among files in your program, and the states the commands for updating each file. In a program, typically the executable file is updated from object files, which are in turn made by compiling source files.

Options

Tag	Description
-b, -m	prints online help and exitThese options are ignored for compatibility with other versions of make..
-B, --always-make	Unconditionally make all targets.
-C dir, --directory=dir	Change to directory dir before reading the makefiles or doing anything else. If multiple -C options are specified, each is interpreted relative to the previous one: -C / -C etc is equivalent to -C /etc. This is typically used with recursive invocations of make.
-d	Print debugging information in addition to normal processing. The debugging information says which files are being considered for remaking, which file-times are being compared and with what results, which files actually need to be remade, which implicit rules are considered and which are applied---everything interesting about how make decides what to do.
--debug[=FLAGS]	Print debugging information in addition to normal processing. If the FLAGS are omitted, then the behavior is the same as if -d was specified. FLAGS may be a for all debugging output (same as using -d), b for basic debugging, v for more verbose basic debugging, i for showing implicit rules, j for details on invocation of commands, and m for debugging while remaking makefiles.
-e,--environment-overrides	Give variables taken from the environment precedence over variables from makefiles.
+-f file, --file=file, --makefile=FILE	Use file as a makefile.
-i, --ignore-errors	Ignore all errors in commands executed to remake files.
-I dir, --include-dir=dir	Specifies a directory dir to search for included makefiles. If several -I options are used to specify several directories, the directories are searched in the order specified. Unlike the arguments to other flags of make, directories given with -I flags may come directly after the flag: -Idir is allowed, as well as -I dir. This syntax is allowed for compatibility with the C preprocessor's -I flag.
-j [jobs], --jobs[=jobs]	Specifies the number of jobs (commands) to run simultaneously. If there is more than one -j option, the last one is effective. If the -j option is given without an argument, make will not limit the number of jobs that can run simultaneously.
-k, --keep-going	Continue as much as possible after an error. While the target that failed, and those that depend on it, cannot be remade, the other dependencies of these targets can be processed all the same.
-l [load], --load-average[=load]	Specifies that no new jobs (commands) should be started if there are others jobs running and the load average is at least load (a floating-point number). With no argument, removes a previous load limit.
-L, --check-symlink-times	Use the latest mtime between symlinks and target.
-n, --just-print, --dry-run, --recon	Print the commands that would be executed, but do not execute them.
-o file, --old-file=file, --assume-old=file	Do not remake the file file even if it is older than its dependencies, and do not remake anything on account of changes in file. Essentially the file is treated as very old and its rules are ignored.
-p, --print-data-base	Print the data base (rules and variable values) that results from reading the makefiles; then execute as usual or as otherwise specified. This also prints the version information given by the -v switch.
-q, --question	''Question mode''. Do not run any commands, or print anything; just return an exit status that is zero if the specified targets are already up to date, nonzero otherwise.
-r, --no-builtin-rules	Eliminate use of the built-in implicit rules. Also clear out the default list of suffixes for suffix rules.
-R, --no-builtin-variables	Don't define any built-in variables.
-s, --silent, --quiet	Silent operation; do not print the commands as they are executed.
-S, --no-keep-going, --stop	Cancel the effect of the -k option. This is never necessary except in a recursive make where -k might be inherited from the top-level make via MAKEFLAGS or if you set -k in MAKEFLAGS in your environment.
-t, --touch	Touch files (mark them up to date without really changing them) instead of running their commands. This is used to pretend that the commands were done, in order to fool future invocations of make.
-v, --version	Print the version of the make program plus a copyright, a list of authors and a notice that there is no warranty.
-w, --print-directory	Print a message containing the working directory before and after other processing. This may be useful for tracking down errors from complicated nests of recursive make commands.
--no-print-directory	Turn off -w, even if it was turned on implicitly.
-W file, --what-if=file, --new-file=file, --assume-new=file	Pretend that the target file has just been modified. When used with the -n flag, this shows you what would happen if you were to modify that file. Without -n, it is almost the same as running a touch command on the given file before running make, except that the modification time is changed only in the imagination of make.
--warn-undefined-variables	Warn when an undefined variable is referenced.

EXAMPLES

Example-1:

To Build your programs:

$ make

output:

 gcc -c -Wall test1.c
 gcc -c -Wall test2.c
 gcc -Wall test1.o test2.o -o test 

Note: make reads makefile present in current directory and executes based on statements in makefile

Example-2:

To clean all the object files:

$ make clean

output:

 rm -rf *.o test

Example-3:

To forcibly build all programs, use -B option:

$ make -B

output:

 gcc -c -Wall test.c
 gcc -c -Wall anotherTest.c
 gcc -Wall test.o anotherTest.o -o test

Example-4:

To run make in debug mode, use the -d option :

$ make -d

output:

Copyright (C) 2006 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
This program built for x86_64-pc-linux-gnu

Reading makefiles...
Reading makefile `Makefile'...
Updating makefiles....
Considering target file `Makefile'.
Looking for an implicit rule for `Makefile'.
Trying pattern rule with stem `Makefile'.
Trying implicit prerequisite `Makefile.o'.
Trying pattern rule with stem `Makefile'.
Trying implicit prerequisite `Makefile.c'.
Trying pattern rule with stem `Makefile'.
Trying implicit prerequisite `Makefile.cc'.
Trying pattern rule with stem `Makefile'.
Trying implicit prerequisite `Makefile.C'.
Trying pattern rule with stem `Makefile'.
Trying implicit prerequisite `Makefile.cpp'.
Trying pattern rule with stem `Makefile'.
--More--

Example-5:

To build programs present in different directory:

$ make -C /home/testdir/

output:

make: Entering directory `/home/himanshu/practice/make-dir'
make: Nothing to be done for `all'.
make: Leaving directory `/home/himanshu/practice/make-dir'

Example-6:

To use other file instead of default makefile, use -f option :

$ make -f my_makefile

output:

gcc -c -Wall test1.c
gcc -c -Wall test2.c
gcc -Wall test1.o test2.o -o test

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