Understanding the -q Option in GNU Make

Purpose

• The -q (or --quiet) option in GNU Make instructs the tool to suppress the normal output it generates while processing your Makefile.

Normal Output

• By default, make typically prints:
  • Information about the targets it's considering and their prerequisites.
  • The actual commands being executed (unless you use the @ directive in the recipe itself).
  • Messages about files being updated or skipped.

What -q Does

• With -q, this output is entirely silenced, resulting in a more streamlined and less verbose execution. This can be helpful when you're only interested in whether the build succeeded or failed, not the individual steps taken.

Example

Consider a simple Makefile with a target clean:

clean:
        rm -f *.o

Without -q:

$ make clean
rm -f *.o

With -q:

$ make -q clean

In the second case, you won't see the "rm -f *.o" command printed.

• If you need to see the output even with -q, you can use the @ directive within a recipe to silence specific commands within the Makefile itself.
• -q can be combined with other options like -v (verbose) to achieve a specific level of output control. For instance, make -qv would print the version information (-v) but suppress the rest of the output (-q).

---

Basic Compilation with -q

This example builds an executable named myprogram from source files main.c and helper.c using GCC.

Makefile

CC=gcc

myprogram: main.o helper.o
        $(CC) -o myprogram main.o helper.o

main.o: main.c helper.h
        $(CC) -c main.c

helper.o: helper.c helper.h
        $(CC) -c helper.c

clean:
        rm -f *.o myprogram

Execution

# Normal output
$ make
cc -c main.c
cc -c helper.c
cc -o myprogram main.o helper.o

# Suppressed output with -q
$ make -q

Multi-Target Build with -q

This example builds both an executable (myprogram) and a compressed archive (myprogram.tar.gz) with -q.

Makefile

CC=gcc

myprogram: main.o helper.o
        $(CC) -o myprogram main.o helper.o

myprogram.tar.gz: myprogram
        tar -czf myprogram.tar.gz myprogram

clean:
        rm -f *.o myprogram myprogram.tar.gz

Execution

# Normal output
$ make
cc -c main.c
cc -c helper.c
cc -o myprogram main.o helper.o
tar -czf myprogram.tar.gz myprogram

# Suppressed output with -q
$ make -q

Debugging with -q and @

This example shows how to use -q and @ together. It builds myprogram with -q but keeps the compilation commands visible within the Makefile using @.

Makefile

CC=gcc

myprogram: main.o helper.o
        $(CC) -o myprogram main.o helper.o

main.o: main.c helper.h
        @$(CC) -c main.c  # This command will still be printed

helper.o: helper.c helper.h
        @$(CC) -c helper.c  # This command will still be printed

clean:
        rm -f *.o myprogram

# Commands shown within the Makefile, output otherwise suppressed
$ make -q

---

Filtering Output with Grep

• If you only want a specific type of message (e.g., errors, warnings), you can use grep with make:

$ make 2>&1 | grep -i 'error\|warning'  # Capture standard error (2>&1) and filter for errors/warnings

Selective Output with @ Directive

• Within your Makefile, use the @ directive to suppress specific commands within recipes. This allows you to control the verbosity on a per-command basis:

clean:
        @rm -f *.o  # This command won't be printed
        rm -f myprogram

Customizing Output with Variables

• For more granular control, use variables like SILENT or VERBOSE within your Makefile. Set them based on command-line options or environment variables:

ifeq ($(SILENT),1)
  # Define commands with @ here
else
  # Define commands normally here
endif

Using a Different Build System

• If you need a significantly different level of control over build output, consider alternative build systems like:
  • CMake: Offers a more structured approach to build configuration, potentially leading to less output by default.
  • Ninja: Known for its focus on speed and minimal output.

Choosing the Right Approach

The best alternative to -q depends on your specific needs:

• Significantly Different Level of Control
  Different build system
• Granular Control
  Custom variables
• Suppressing Specific Commands
  @ directive
• Filtering Specific Messages
  grep