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

frontend/lb

@@ -20,7 +20,7 @@ USAGE="lb {clean|config|build}"
 
 case "${1}" in
 	-h|--help)
-		if [ -x "$(which man 2>/dev/null)" ]
+		if [ $(which man) ]
 		then
 			man lb
 			exit 0
@@ -75,7 +75,7 @@ case "${1}" in
 		then
 			# User has live-build installed in the system
 			SCRIPT=/usr/lib/live/build/"${COMMAND}"
-		elif [ -x "$(which ${COMMAND} 2>/dev/null)" ]
+		elif [ $(which "${COMMAND}") ]
 		then
 			# User has live-build commands in path
 			SCRIPT="${COMMAND}"

frontend/live-build

@@ -22,7 +22,7 @@
 
 set -e
 
-if [ -x "$(which man 2>/dev/null)" ]
+if [ $(which man) ]
 then
 	man live-build
 else

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

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."
 

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

functions/man.sh

@@ -10,7 +10,7 @@
 
 Man ()
 {
-	if [ -x "$(which man 2>/dev/null)" ]
+	if [ $(which man) ]
 	then
 		man $(basename ${0})
 		exit 0

scripts/build/bootstrap_debootstrap

@@ -24,7 +24,7 @@ Arguments "${@}"
 Read_conffiles config/all config/common config/bootstrap config/chroot config/binary config/source
 Set_defaults
 
-if [ ! -x "$(which debootstrap 2>/dev/null)" ]
+if [ ! $(which debootstrap) ]
 then
 	Echo_error "debootstrap - command not found"
 	Echo_verbose "debootstrap can be obtained from http://ftp.debian.org/debian/pool/main/d/debootstrap/"
@@ -76,7 +76,7 @@ then
 	DEBOOTSTRAP_OPTIONS="${DEBOOTSTRAP_OPTIONS} --no-check-gpg"
 fi
 
-if [ -x "/usr/sbin/debootstrap" ]
+if [ $(which debootstrap) ]
 then
 	if [ "${LB_CACHE_PACKAGES}" = "true" ]
 	then
@@ -126,6 +126,6 @@ then
 	# Creating stage file
 	Create_stagefile .build/bootstrap
 else
-	Echo_error "Can't process file /usr/bin/debootstrap (FIXME)"
+	Echo_error "Can't find program debootstrap (FIXME)"
 	exit 1
 fi

scripts/build/chroot_archives

@@ -242,7 +242,7 @@ case "${1}" in
 				cp -f cache/indices.bootstrap/*Release* chroot/var/lib/apt/lists
 			fi
 
-			if [ "${LB_APT}" = "aptitude" ] && [ ! -x /usr/bin/aptitude ]
+			if [ "${LB_APT}" = "aptitude" ] && [ ! $(which aptitude) ]
 			then
 				Chroot chroot "apt-get ${APT_OPTIONS} update"
 				Chroot chroot "apt-get ${APT_OPTIONS} install aptitude"
@@ -260,7 +260,7 @@ case "${1}" in
 			fi
 
 			# Installing aptitude
-			if [ "${LB_APT}" = "aptitude" ] && [ ! -x /chroot/usr/bin/aptitude ]
+			if [ "${LB_APT}" = "aptitude" ] && [ ! $(Chroot chroot "which aptitude") ]
 			then
 				Chroot chroot "apt-get ${APT_OPTIONS} update"
 				Chroot chroot "apt-get ${APT_OPTIONS} install aptitude"

scripts/build/config

@@ -178,7 +178,7 @@ Local_arguments ()
 		case "${1}" in
 			--dump)
 				# Dump version
-				if [ -x "$(which dpkg-query 2>/dev/null)" ]
+				if [ $(which dpkg-query) ]
 				then
 					VERSION_DPKG="$(dpkg-query -f='${Version}' --show live-build)"
 				fi

share/bin/Packages

@@ -10,9 +10,9 @@
 
 set -e
 
-if [ ! -e /usr/bin/grep-aptavail ]
+if [ ! $(which grep-aptavail) ]
 then
-	echo "E: /usr/bin/grep-aptavail: No such file."
+	echo "E: program grep-aptavail not found!"
 
 	exit 1
 fi

share/hooks/normal/0400-update-apt-file-cache.hook.chroot

@@ -8,7 +8,7 @@ set -e
 
 . /live-build/config/binary
 
-if [ -x /usr/bin/apt-file ] && [ "${LB_APT_INDICES}" = "true" ]
+if [ $(which apt-file) ] && [ "${LB_APT_INDICES}" = "true" ]
 then
 	apt-file update
 fi

share/hooks/normal/0410-update-apt-xapian-index.hook.chroot

@@ -8,7 +8,7 @@ set -e
 # is not allowed to, and (b) it wants to build the index in the background which
 # will be racy in the context of live-build.
 
-if [ -x /usr/sbin/update-apt-xapian-index ]
+if [ $(which update-apt-xapian-index) ]
 then
 	PYTHONDONTWRITEBYTECODE=1 /usr/sbin/update-apt-xapian-index --force --quiet
 fi

share/hooks/normal/0430-update-mlocate-database.hook.chroot

@@ -8,7 +8,7 @@ set -e
 # means that if the live system is later installed to a hard disk then less
 # work will be required after installation.
 
-if [ -x /usr/bin/updatedb.mlocate ]
+if [ $(which updatedb.mlocate) ]
 then
 	updatedb.mlocate
 fi