Replace 'which' with 'command -v' to test for the existance of an executable

This is considered to be more robust.

Two instances remain:

scripts/build/chroot_archives, line 257:
if [ "${LB_APT}" = "aptitude" ] && [ ! $(Chroot chroot "which aptitude") ]
The command is run inside a chroot where the environment might be special,
and would need further testing.

manpages/Makefile, line 42:
@if [ ! -x "$$(which po4a 2>/dev/null)" ]; \
I am insufficiently familiar with makefile syntax to edit this.

frontend/live-build

@@ -23,7 +23,7 @@
 
 set -e
 
-if [ $(which man) ]
+if command -v man >/dev/null
 then
 	man live-build
 else

functions/architectures.sh

@@ -53,7 +53,7 @@ Check_architectures ()
 Check_crossarchitectures ()
 {
 	local HOST
-	if [ $(which dpkg) ]
+	if command -v dpkg >/dev/null
 	then
 		HOST="$(dpkg --print-architecture)"
 	else

functions/configuration.sh

@@ -36,7 +36,7 @@ Prepare_config ()
 
 	LB_SYSTEM="${LB_SYSTEM:-live}"
 
-	if [ $(which lsb_release) ]
+	if command -v lsb_release >/dev/null
 	then
 		local _DISTRIBUTOR
 		_DISTRIBUTOR="$(lsb_release -is | tr "[A-Z]" "[a-z]")"
@@ -66,7 +66,7 @@ Prepare_config ()
 	LIVE_IMAGE_TYPE="${LB_IMAGE_TYPE}"
 
 	if [ -z "${LB_ARCHITECTURE}" ]; then
-		if [ $(which dpkg) ]; then
+		if command -v dpkg >/dev/null; then
 			LB_ARCHITECTURE="$(dpkg --print-architecture)"
 		else
 			case "$(uname -m)" in
@@ -688,7 +688,7 @@ Validate_config_permitted_values ()
 # Check option combinations and other extra stuff
 Validate_config_dependencies ()
 {
-	if [ "${LB_BINARY_FILESYSTEM}" = "ntfs" ] && [ ! $(which ntfs-3g) ]; then
+	if [ "${LB_BINARY_FILESYSTEM}" = "ntfs" ] && ! command -v ntfs-3g >/dev/null; then
 		Echo_error "Using ntfs as the binary filesystem is currently only supported if ntfs-3g is installed on the host system."
 		exit 1
 	fi

functions/losetup.sh

@@ -22,7 +22,7 @@ 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 [ $(which udevadm) ]
+	if command -v udevadm >/dev/null
 	then
 		udevadm settle
 	fi

functions/man.sh

@@ -13,7 +13,7 @@ Man ()
 {
 	local BASENAME
 	BASENAME=$(basename ${0})
-	if [ $(which man) ]
+	if command -v man >/dev/null
 	then
 		case $BASENAME in
 			$PROGRAM)

functions/packages.sh

@@ -82,7 +82,7 @@ Check_installed ()
 			INSTALL_STATUS=1
 		fi
 	else
-		if [ $(which dpkg-query) ]
+		if command -v dpkg-query >/dev/null
 		then
 			if dpkg-query -s "${PACKAGE}" 2> /dev/null | grep -qs "Status: install"
 			then

scripts/build/bootstrap_debootstrap

@@ -21,7 +21,7 @@ USAGE="${PROGRAM} [--force]"
 # Processing arguments and configuration files
 Init_config_data "${@}"
 
-if [ ! $(which debootstrap) ]
+if ! command -v debootstrap >/dev/null
 then
 	Echo_error "debootstrap - command not found"
 	Echo_verbose "debootstrap can be obtained from http://ftp.debian.org/debian/pool/main/d/debootstrap/"

scripts/build/chroot_archives

@@ -236,7 +236,7 @@ case "${_ACTION}" in
 				cp -f cache/indices.bootstrap/*Release* chroot/var/lib/apt/lists
 			fi
 
-			if [ "${LB_APT}" = "aptitude" ] && [ ! $(which aptitude) ]
+			if [ "${LB_APT}" = "aptitude" ] && ! command -v aptitude >/dev/null
 			then
 				Chroot chroot "apt-get ${APT_OPTIONS} update"
 				Chroot chroot "apt-get ${APT_OPTIONS} install aptitude"

scripts/build/config

@@ -212,7 +212,7 @@ Local_arguments ()
 			--dump)
 				# Dump version
 				Echo "This is live-build version %s" "${VERSION}"
-				if [ $(which dpkg-query) ]; then
+				if command -v dpkg-query >/dev/null; then
 					Echo "Installed version reported by dpkg is %s" "$(dpkg-query -f='${Version}' --show live-build)"
 				fi
 

share/bin/Packages

@@ -11,7 +11,7 @@
 
 set -e
 
-if [ ! $(which grep-aptavail) ]
+if ! command -v grep-aptavail >/dev/null
 then
 	echo "E: program grep-aptavail not found!"
 

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

@@ -8,7 +8,7 @@ set -e
 
 . /live-build/config/binary
 
-if [ $(which apt-file) ] && [ "${LB_APT_INDICES}" = "true" ]
+if command -v apt-file >/dev/null && [ "${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 [ $(which update-apt-xapian-index) ]
+if command -v update-apt-xapian-index >/dev/null
 then
 	PYTHONDONTWRITEBYTECODE=1 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 [ $(which updatedb.mlocate) ]
+if command -v updatedb.mlocate >/dev/null
 then
 	updatedb.mlocate
 fi