Suppress "nothing to be done for 'all' "

I am writing a short shell script which calls 'make all'. It's not critical, but is there a way I can suppress the message saying 'nothing to be done for all' if that is the case? I am hoping to find a flag for 开发者_如何学Pythonmake which suppresses this (not sure there is one), but an additional line or 2 of code would work too.

FYI I'm using bash.

Edit: to be more clear, I only want to suppess messages that therer is nothing to be done. Otherwise, I want to display the output.

You can make "all" a PHONY target (if it isn't already) which has the real target as a prerequisite, and does something inconspicuous:

.PHONY: all

all: realTarget
    @echo > /dev/null

I would like to improve on the previous solution, just to make it a little bit more efficient...:)

.PHONY: all
all: realTarget
        @:

@true would also work but is a little slower than @: (I've done some performance tests). In any case both are quite faster than "echo > /dev/null"...

The flag -s silences make: make -s all

EDIT: I originally answered that the flag -q silenced make. It works for me, although the manpage specifies -s, --silent, --quiet as the valid flags.

The grep solution:

{ make all 2>&1 1>&3 | grep -v 'No rule to make target `all' >&2; } 3>&1 

The construct 2>&1 1>&3 sends make's stdout to fd 3 and make's stderr to stdout. grep then reads from the previous command's stdout, removes the offending line and sends its stdout to stderr. Finally, fd 3 is returned to stdout.

2022-11-17, A response to @Pryftan's comment:

Ignoring the minor error that I used the wrong text.

Lets create a function that outputs some stuff

make() {
    echo "this is stdout"
    echo "this is stderr" >&2
    printf 'oops, No rule to make target `%s`, not at all' "$1" >&2
}

Testing my solution:

$ { make foobar 2>&1 1>&3 | grep -v 'No rule to make target `all' >&2; } 3>&1
this is stdout
this is stderr
oops, No rule to make target `foobar`, not at all

$ { make all 2>&1 1>&3 | grep -v 'No rule to make target `all' >&2; } 3>&1
this is stdout
this is stderr

Looks good so far.

What about without the braces?

$ make all 2>&1 1>&3 | grep -v 'No rule to make target `all' >&2 3>&1
bash: 3: Bad file descriptor

In this case, we'd need to explicitly create fd 3

$ exec 3>&1; make all 2>&1 1>&3 | grep -v 'No rule to make target `all' >&2 3>&1
this is stdout
this is stderr

What is it about the braces? I think it's delaying evaluation of the contents, and that allows the trailing 3>&1 to be processed first. And that makes the inner 1>&3 valid.