fix consistency in binary execution and existance checking

 - prefer using `which` over hard coded paths
 - it is redundant to check that the bin pointed to the return of
   `which` exists and is executable, `which` already gives us
   assurance of that if it returns true!
 - the redirection of output (`2>/dev/null`) seems to be
   unnecessary from my testing.

the instances relatnig to fdisk and losetup in functions/defaults.sh have
been left as they are since they get executed by `lb config` which can run
without sudo elevation unlike `lb build` and in that case `which` would
fail to find these binaries resulting in error.

this also fixes a bug showing an error for missing debootstrap - this tool
requires sudo privileges to run and thus is not found via a none elevated
which search.

Gbp-Dch: Short
Closes: #952927

4 files changed, 6 insertions, 6 deletions

diff --git a/functions/architectures.sh b/functions/architectures.sh
index 7c6c48cff..393d217e8 100755
--- a/functions/architectures.sh
+++ b/functions/architectures.sh
@@ -49,7 +49,7 @@ Check_architectures ()
 
 Check_crossarchitectures ()
 {
-	if [ -x /usr/bin/dpkg ]
+	if [ $(which dpkg) ]
 	then
 		HOST="$(dpkg --print-architecture)"
 	else
diff --git a/functions/defaults.sh b/functions/defaults.sh
index d254b079a..ed271ebc9 100755
--- a/functions/defaults.sh
+++ b/functions/defaults.sh
@@ -13,7 +13,7 @@ New_configuration ()
 	## Runtime
 
 	# Image: Architecture
-	if [ -x "/usr/bin/dpkg" ]
+	if [ $(which dpkg) ]
 	then
 		CURRENT_IMAGE_ARCHITECTURE="$(dpkg --print-architecture)"
 	else
@@ -93,7 +93,7 @@ Set_defaults ()
 	LB_SYSTEM="${LB_SYSTEM:-live}"
 
 	# Setting mode (currently: debian, progress-linux)
-	if [ -x /usr/bin/lsb_release ]
+	if [ $(which lsb_release) ]
 	then
 		_DISTRIBUTOR="$(lsb_release -is | tr "[A-Z]" "[a-z]")"
 
@@ -826,7 +826,7 @@ Check_defaults ()
 {
 	case "${LB_BINARY_FILESYSTEM}" in
 		ntfs)
-			if [ ! -x "$(which ntfs-3g 2>/dev/null)" ]
+			if [ ! $(which ntfs-3g) ]
 			then
 				Echo_error "Using ntfs as the binary filesystem is currently only supported if ntfs-3g is installed on the host system."
 
diff --git a/functions/losetup.sh b/functions/losetup.sh
index 9d9b46e5d..cdf984b74 100755
--- a/functions/losetup.sh
+++ b/functions/losetup.sh
@@ -21,7 +21,7 @@ Lodetach ()
 	# Changes to block devices result in uevents which trigger rules which in
 	# turn access the loop device (ex. udisks-part-id, blkid) which can cause
 	# a race condition. We call 'udevadm settle' to help avoid this.
-	if [ -x "$(which udevadm 2>/dev/null)" ]
+	if [ $(which udevadm) ]
 	then
 		udevadm settle
 	fi
diff --git a/functions/man.sh b/functions/man.sh
index 11366b7b4..7896f5a9c 100755
--- a/functions/man.sh
+++ b/functions/man.sh
@@ -10,7 +10,7 @@
 
 Man ()
 {
-	if [ -x "$(which man 2>/dev/null)" ]
+	if [ $(which man) ]
 	then
 		man $(basename ${0})
 		exit 0