makefiles: Replace which with command -v

As the POSIX documentation[1] of `command -v` guarantees that on error
there will be no output (and there will be output in the other cases),
the tests in Makefiles were simplified to test for output equality to
the empty string.

Redirects swallowing error outputs were removed, as the command produces
no error output there (as recommended at [2]).

Existing uses of `command` are simplified as well.

[1]: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/command.html
[2]: https://salsa.debian.org/debian/debianutils/-/blob/master/debian/NEWS

.github/workflows/release-test.yml

@@ -150,7 +150,7 @@ jobs:
           TTN_DEV_ID="riot_lorawan_1" \
           TTN_DEV_ID_ABP="riot_lorawan_1_abp" \
           RIOTBASE=${RIOTBASE} \
-          $(which tox) -e test -- ${TOX_ARGS} \
+          $(command -v tox) -e test -- ${TOX_ARGS} \
             ${K} "${{ github.event.inputs.filter }}" -m "${{ matrix.pytest_mark }}"
     - name: junit2html and XML deploy
       if: always()

Makefile.include

@@ -327,13 +327,13 @@ APPLICATION := $(strip $(APPLICATION))
 
 ifeq (,$(and $(DOWNLOAD_TO_STDOUT),$(DOWNLOAD_TO_FILE)))
   ifeq (,$(WGET))
-    ifeq (0,$(shell which wget > /dev/null 2>&1 ; echo $$?))
-      WGET = $(call memoized,WGET,$(shell which wget))
+    ifeq (,$(shell command -v wget))
+      WGET = $(call memoized,WGET,$(shell command -v wget))
     endif
   endif
   ifeq (,$(CURL))
-    ifeq (0,$(shell which curl > /dev/null 2>&1 ; echo $$?))
-      CURL = $(call memoized,CURL,$(shell which curl))
+    ifneq (,$(shell command -v curl))
+      CURL = $(call memoized,CURL,$(shell command -v curl))
     endif
   endif
   ifeq (,$(WGET)$(CURL))
@@ -349,11 +349,11 @@ ifeq (,$(and $(DOWNLOAD_TO_STDOUT),$(DOWNLOAD_TO_FILE)))
 endif
 
 ifeq (,$(UNZIP_HERE))
-  ifeq (0,$(shell which unzip > /dev/null 2>&1 ; echo $$?))
-    UNZIP_HERE = $(call memoized,UNZIP_HERE,$(shell which unzip) -q)
+  ifneq (,$(shell command -v unzip))
+    UNZIP_HERE = $(call memoized,UNZIP_HERE,$(shell command -v unzip) -q)
   else
-    ifeq (0,$(shell which 7z > /dev/null 2>&1 ; echo $$?))
-      UNZIP_HERE = $(call memoized,UNZIP_HERE,$(shell which 7z) x -bd)
+    ifneq (,$(shell command -v 7z))
+      UNZIP_HERE = $(call memoized,UNZIP_HERE,$(shell command -v 7z) x -bd)
     else
       $(warning Neither unzip nor 7z is installed.)
     endif

dist/testbed-support/makefile.iotlab.single.inc.mk

@@ -57,7 +57,7 @@ endif
 IOTLAB_AUTH ?= $(HOME)/.iotlabrc
 IOTLAB_USER ?= $(shell cut -f1 -d: $(IOTLAB_AUTH))
 
-ifneq (0,$(shell command -v iotlab-experiment -h 2>&1 > /dev/null ; echo $$?))
+ifeq (,$(shell command -v iotlab-experiment))
   $(info $(COLOR_RED)'iotlab-experiment' command is not available \
 	        please consider installing it from \
 	        https://pypi.python.org/pypi/iotlabcli$(COLOR_RESET))
@@ -66,7 +66,7 @@ endif
 
 ifeq (iotlab-a8-m3,$(BOARD))
   ifneq (,$(filter flash% reset,$(MAKECMDGOALS)))
-    ifneq (0,$(shell command -v iotlab-ssh -h 2>&1 > /dev/null ; echo $$?))
+    ifeq (,$(shell command -v iotlab-ssh))
       $(info $(COLOR_RED)'iotlab-ssh' command is not available \
 	          please consider installing it from \
 	          https://pypi.python.org/pypi/iotlabsshcli$(COLOR_RESET))

dist/tools/openvisualizer/makefile.openvisualizer.inc.mk

@@ -34,9 +34,9 @@
 #
 
 # Use full path in case it needs to be run with sudo
-OPENV_SERVER_PATH := $(shell which openv-server)
-OPENV_CLIENT_PATH := $(shell which openv-client)
-OPENV_SERIAL_PATH := $(shell which openv-serial)
+OPENV_SERVER_PATH := $(shell command -v openv-server)
+OPENV_CLIENT_PATH := $(shell command -v openv-client)
+OPENV_SERIAL_PATH := $(shell command -v openv-serial)
 
 # Openvisualizer requires to know where openwsn-fw is located
 OPENV_OPENWSN_FW_PATH ?= --fw-path=$(RIOTBASE)/build/pkg/openwsn

makefiles/arch/riscv.inc.mk

@@ -25,7 +25,7 @@ TARGET_ARCH_RISCV ?= \
     $(subst -gcc,,\
       $(notdir \
         $(word 1,\
-          $(foreach triple,$(_TRIPLES_TO_TEST),$(shell which $(triple)-gcc 2> /dev/null))))))
+          $(foreach triple,$(_TRIPLES_TO_TEST),$(shell command -v $(triple)-gcc))))))
 
 TARGET_ARCH ?= $(TARGET_ARCH_RISCV)
 

makefiles/boards/sam0.inc.mk

@@ -29,7 +29,7 @@ ifeq ($(PROGRAMMER),)
     PROGRAMMER ?= edbg
   else ifeq ($(OPENOCD_DEBUG_ADAPTER),jlink)
     # only use JLinkExe if it's installed
-    ifneq (,$(shell which JLinkExe))
+    ifneq (,$(shell command -v JLinkExe))
       PROGRAMMER ?= jlink
     else
       PROGRAMMER ?= openocd

pkg/flatbuffers/Makefile.include

@@ -2,7 +2,7 @@ INCLUDES += -I$(PKGDIRBASE)/flatbuffers/include
 
 FLATC ?= flatc
 
-ifneq (0,$(shell which flatc > /dev/null 2>&1 ; echo $$?))
+ifeq (,$(shell command -v flatc ))
   FLATC = $(RIOTTOOLS)/flatc/flatc
   $(call target-export-variables,all,FLATC)
 endif