make: Instead of Execution
9.3 Instead of Executing Recipes
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The makefile tells 'make' how to tell whether a target is up to date,
and how to update each target. But updating the targets is not always
what you want. Certain options specify other activities for 'make'.
'-n'
'--just-print'
'--dry-run'
'--recon'
"No-op". Causes 'make' to print the recipes that are needed to
make the targets up to date, but not actually execute them. Note
that some recipes are still executed, even with this flag (
How the 'MAKE' Variable Works MAKE Variable.). Also any recipes
needed to update included makefiles are still executed (How
Makefiles Are Remade Remaking Makefiles.).
'-t'
'--touch'
"Touch". Marks targets as up to date without actually changing
them. In other words, 'make' pretends to update the targets but
does not really change their contents; instead only their modified
times are updated.
'-q'
'--question'
"Question". Silently check whether the targets are up to date, but
do not execute recipes; the exit code shows whether any updates are
needed.
'-W FILE'
'--what-if=FILE'
'--assume-new=FILE'
'--new-file=FILE'
"What if". Each '-W' flag is followed by a file name. The given
files' modification times are recorded by 'make' as being the
present time, although the actual modification times remain the
same. You can use the '-W' flag in conjunction with the '-n' flag
to see what would happen if you were to modify specific files.
With the '-n' flag, 'make' prints the recipe that it would normally
execute but usually does not execute it.
With the '-t' flag, 'make' ignores the recipes in the rules and uses
(in effect) the command 'touch' for each target that needs to be remade.
The 'touch' command is also printed, unless '-s' or '.SILENT' is used.
For speed, 'make' does not actually invoke the program 'touch'. It does
the work directly.
With the '-q' flag, 'make' prints nothing and executes no recipes,
but the exit status code it returns is zero if and only if the targets
to be considered are already up to date. If the exit status is one,
then some updating needs to be done. If 'make' encounters an error, the
exit status is two, so you can distinguish an error from a target that
is not up to date.
It is an error to use more than one of these three flags in the same
invocation of 'make'.
The '-n', '-t', and '-q' options do not affect recipe lines that
begin with '+' characters or contain the strings '$(MAKE)' or '${MAKE}'.
Note that only the line containing the '+' character or the strings
'$(MAKE)' or '${MAKE}' is run regardless of these options. Other lines
in the same rule are not run unless they too begin with '+' or contain
'$(MAKE)' or '${MAKE}' (How the 'MAKE' Variable Works MAKE
Variable.)
The '-t' flag prevents phony targets (Phony Targets) from
being updated, unless there are recipe lines beginning with '+' or
containing '$(MAKE)' or '${MAKE}'.
The '-W' flag provides two features:
* If you also use the '-n' or '-q' flag, you can see what 'make'
would do if you were to modify some files.
* Without the '-n' or '-q' flag, when 'make' is actually executing
recipes, the '-W' flag can direct 'make' to act as if some files
had been modified, without actually running the recipes for those
files.
Note that the options '-p' and '-v' allow you to obtain other
information about 'make' or about the makefiles in use (Summary of
Options Options Summary.).
Info Catalog
make: Goals
make: Running
make: Avoiding Compilation