Turn shellcheck into a normal make target. Fix new files it caught

This checks every file it checked (and a few more),
but explicitly instead of "if it works it works" best-effort
(which wasn't that good anyway)

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Ahelenia Ziemiańska <[email protected]>
Closes #10512
Closes #12101

39 files changed, 213 insertions, 107 deletions

diff --git a/Makefile.am b/Makefile.am
index 689816bdc..4fd3f9b3d 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,3 +1,5 @@
+include $(top_srcdir)/config/Shellcheck.am
+
 ACLOCAL_AMFLAGS = -I config
 
 SUBDIRS = include
@@ -123,17 +125,8 @@ cstyle:
 
 filter_executable = -exec test -x '{}' \; -print
 
-PHONY += shellcheck
-shellcheck:
-	@if type shellcheck > /dev/null 2>&1; then \
-		shellcheck --exclude=SC1090,SC1117,SC1091 --format=gcc \
-			$$(find ${top_srcdir} -name "config*" -prune -name tests -prune \
-				-o -name "*.sh" -o -name "*.sh.in" -type f) \
-			$$(find ${top_srcdir}/cmd/zpool/zpool.d/* \
-			-type f ${filter_executable}); \
-	else \
-		echo "skipping shellcheck because shellcheck is not installed"; \
-	fi
+SHELLCHECKDIRS = cmd contrib etc scripts tests
+SHELLCHECKSCRIPTS = autogen.sh
 
 PHONY += checkabi storeabi
 checkabi: lib
diff --git a/cmd/Makefile.am b/cmd/Makefile.am
index a3db31679..5fc9e8397 100644
--- a/cmd/Makefile.am
+++ b/cmd/Makefile.am
@@ -1,3 +1,5 @@
+include $(top_srcdir)/config/Shellcheck.am
+
 SUBDIRS  = zfs zpool zdb zhack zinject zstream ztest
 SUBDIRS += fsck_zfs vdev_id raidz_test zfs_ids_to_path
 SUBDIRS += zpool_influxdb
@@ -5,6 +7,9 @@ SUBDIRS += zpool_influxdb
 CPPCHECKDIRS  = zfs zpool zdb zhack zinject zstream ztest
 CPPCHECKDIRS += raidz_test zfs_ids_to_path zpool_influxdb
 
+# TODO: #12084: SHELLCHECKDIRS = fsck_zfs vdev_id zpool
+SHELLCHECKDIRS = fsck_zfs zpool
+
 if USING_PYTHON
 SUBDIRS += arcstat arc_summary dbufstat
 endif
@@ -12,6 +17,7 @@ endif
 if BUILD_LINUX
 SUBDIRS += mount_zfs zed zgenhostid zvol_id zvol_wait
 CPPCHECKDIRS += mount_zfs zed zgenhostid zvol_id
+SHELLCHECKDIRS += zed
 endif
 
 PHONY = cppcheck
diff --git a/cmd/fsck_zfs/Makefile.am b/cmd/fsck_zfs/Makefile.am
index 67583ac75..f8139f117 100644
--- a/cmd/fsck_zfs/Makefile.am
+++ b/cmd/fsck_zfs/Makefile.am
@@ -1,4 +1,5 @@
 include $(top_srcdir)/config/Substfiles.am
+include $(top_srcdir)/config/Shellcheck.am
 
 dist_sbin_SCRIPTS = fsck.zfs
 
diff --git a/cmd/vdev_id/Makefile.am b/cmd/vdev_id/Makefile.am
index fb815faad..4071c6d5e 100644
--- a/cmd/vdev_id/Makefile.am
+++ b/cmd/vdev_id/Makefile.am
@@ -1 +1,3 @@
+include $(top_srcdir)/config/Shellcheck.am
+
 dist_udev_SCRIPTS = vdev_id
diff --git a/cmd/zed/Makefile.am b/cmd/zed/Makefile.am
index 7d2fe124f..5f754c8ae 100644
--- a/cmd/zed/Makefile.am
+++ b/cmd/zed/Makefile.am
@@ -1,8 +1,10 @@
 include $(top_srcdir)/config/Rules.am
+include $(top_srcdir)/config/Shellcheck.am
 
 AM_CFLAGS += $(LIBUDEV_CFLAGS) $(LIBUUID_CFLAGS)
 
 SUBDIRS = zed.d
+SHELLCHECKDIRS = $(SUBDIRS)
 
 sbin_PROGRAMS = zed
 
diff --git a/cmd/zed/zed.d/Makefile.am b/cmd/zed/zed.d/Makefile.am
index 8b2d0c200..3eece353e 100644
--- a/cmd/zed/zed.d/Makefile.am
+++ b/cmd/zed/zed.d/Makefile.am
@@ -1,5 +1,6 @@
 include $(top_srcdir)/config/Rules.am
 include $(top_srcdir)/config/Substfiles.am
+include $(top_srcdir)/config/Shellcheck.am
 
 EXTRA_DIST += README
 
diff --git a/cmd/zpool/Makefile.am b/cmd/zpool/Makefile.am
index 4446cf04a..aad45d4f7 100644
--- a/cmd/zpool/Makefile.am
+++ b/cmd/zpool/Makefile.am
@@ -1,4 +1,5 @@
 include $(top_srcdir)/config/Rules.am
+include $(top_srcdir)/config/Shellcheck.am
 
 AM_CFLAGS += $(LIBBLKID_CFLAGS) $(LIBUUID_CFLAGS)
 
diff --git a/cmd/zpool/zpool.d/smart b/cmd/zpool/zpool.d/smart
index f8854b752..b71591abb 100755
--- a/cmd/zpool/zpool.d/smart
+++ b/cmd/zpool/zpool.d/smart
@@ -53,7 +53,7 @@ get_filename_from_dir()
 	num_files=$(find "$dir" -maxdepth 1 -type f | wc -l)
 	mod=$((pid % num_files))
 	i=0
-	find "$dir" -type f -printf "%f\n" | while read -r file ; do
+	find "$dir" -type f -printf '%f\n' | while read -r file ; do
 		if [ "$mod" = "$i" ] ; then
 			echo "$file"
 			break
@@ -231,11 +231,11 @@ esac
 with_vals=$(echo "$out" | grep -E "$scripts")
 if [ -n "$with_vals" ]; then
 	echo "$with_vals"
-	without_vals=$(echo "$scripts" | tr "|" "\n" |
+	without_vals=$(echo "$scripts" | tr '|' '\n' |
 		grep -v -E "$(echo "$with_vals" |
 		awk -F "=" '{print $1}')" | awk '{print $0"="}')
 else
-	without_vals=$(echo "$scripts" | tr "|" "\n" | awk '{print $0"="}')
+	without_vals=$(echo "$scripts" | tr '|' '\n' | awk '{print $0"="}')
 fi
 
 if [ -n "$without_vals" ]; then
diff --git a/cmd/zvol_wait/Makefile.am b/cmd/zvol_wait/Makefile.am
index 564031c97..2e5bf3323 100644
--- a/cmd/zvol_wait/Makefile.am
+++ b/cmd/zvol_wait/Makefile.am
@@ -1 +1,3 @@
+include $(top_srcdir)/config/Shellcheck.am
+
 dist_bin_SCRIPTS = zvol_wait
diff --git a/config/Shellcheck.am b/config/Shellcheck.am
new file mode 100644
index 000000000..a22333ac4
--- /dev/null
+++ b/config/Shellcheck.am
@@ -0,0 +1,8 @@
+.PHONY: shellcheck
+shellcheck: $(SCRIPTS) $(SHELLCHECKSCRIPTS)
+if HAVE_SHELLCHECK
+	[ -z "$(SCRIPTS)$(SHELLCHECKSCRIPTS)" ] && exit; shellcheck $$([ -n "$(SHELLCHECK_SHELL)" ] && echo "--shell=$(SHELLCHECK_SHELL)") --exclude=SC1090,SC1091$(SHELLCHECK_IGNORE) --format=gcc $(SCRIPTS) $(SHELLCHECKSCRIPTS)
+else
+	@[ -z "$(SCRIPTS)$(SHELLCHECKSCRIPTS)" ] && exit; echo "skipping shellcheck of" $(SCRIPTS) $(SHELLCHECKSCRIPTS) "because shellcheck is not installed"
+endif
+	@set -e; for dir in $(SHELLCHECKDIRS); do $(MAKE) -C $$dir shellcheck; done
diff --git a/config/always-shellcheck.m4 b/config/always-shellcheck.m4
new file mode 100644
index 000000000..1e154e1c5
--- /dev/null
+++ b/config/always-shellcheck.m4
@@ -0,0 +1,7 @@
+dnl #
+dnl # Check if shellcheck is available.
+dnl #
+AC_DEFUN([ZFS_AC_CONFIG_ALWAYS_SHELLCHECK], [
+	AC_CHECK_PROG([SHELLCHECK], [shellcheck], [yes])
+	AM_CONDITIONAL([HAVE_SHELLCHECK], [test "x$SHELLCHECK" = "xyes"])
+])
diff --git a/config/zfs-build.m4 b/config/zfs-build.m4
index cee5c87e7..c4fe07c81 100644
--- a/config/zfs-build.m4
+++ b/config/zfs-build.m4
@@ -207,6 +207,7 @@ AC_DEFUN([ZFS_AC_CONFIG_ALWAYS], [
 	ZFS_AC_CONFIG_ALWAYS_PYZFS
 	ZFS_AC_CONFIG_ALWAYS_SED
 	ZFS_AC_CONFIG_ALWAYS_CPPCHECK
+	ZFS_AC_CONFIG_ALWAYS_SHELLCHECK
 ])
 
 AC_DEFUN([ZFS_AC_CONFIG], [
diff --git a/contrib/Makefile.am b/contrib/Makefile.am
index 9547878d0..5ec13ece5 100644
--- a/contrib/Makefile.am
+++ b/contrib/Makefile.am
@@ -1,3 +1,5 @@
+include $(top_srcdir)/config/Shellcheck.am
+
 SUBDIRS = bash_completion.d pyzfs zcp
 if BUILD_LINUX
 SUBDIRS += bpftrace dracut initramfs
@@ -6,3 +8,5 @@ if PAM_ZFS_ENABLED
 SUBDIRS += pam_zfs_key
 endif
 DIST_SUBDIRS = bash_completion.d bpftrace dracut initramfs pam_zfs_key pyzfs zcp
+
+SHELLCHECKDIRS = bash_completion.d bpftrace dracut initramfs
diff --git a/contrib/bash_completion.d/Makefile.am b/contrib/bash_completion.d/Makefile.am
index 8fbe03688..8c8d1aceb 100644
--- a/contrib/bash_completion.d/Makefile.am
+++ b/contrib/bash_completion.d/Makefile.am
@@ -1,4 +1,5 @@
 include $(top_srcdir)/config/Substfiles.am
+include $(top_srcdir)/config/Shellcheck.am
 
 bashcompletiondir = $(sysconfdir)/bash_completion.d
 
@@ -6,3 +7,7 @@ noinst_DATA = zfs
 
 EXTRA_DIST += $(noinst_DATA)
 SUBSTFILES += $(noinst_DATA)
+
+SHELLCHECKSCRIPTS = $(noinst_DATA)
+SHELLCHECK_SHELL = bash
+SHELLCHECK_IGNORE = ,SC2207
diff --git a/contrib/bash_completion.d/zfs.in b/contrib/bash_completion.d/zfs.in
index f650c8f50..41ce2f871 100644
--- a/contrib/bash_completion.d/zfs.in
+++ b/contrib/bash_completion.d/zfs.in
@@ -139,6 +139,7 @@ __zfs_match_multiple_snapshots()
             fi
             local range_start
             range_start="$(expr "$cur" : '\(.*%\)')"
+            # shellcheck disable=SC2016
             $__ZFS_CMD list -H -o name -s name -t snapshot -d 1 "$base_dataset" | sed 's$.*@$'"$range_start"'$g'
         fi
     else
@@ -163,7 +164,7 @@ __zfs_argument_chosen()
             then
                 return 0
             fi
-            for property in $@
+            for property in "$@"
             do
                 if [[ $prev == "$property"* ]]
                 then
@@ -181,6 +182,7 @@ __zfs_complete_ordered_arguments()
     local list2=$2
     local cur=$3
     local extra=$4
+    # shellcheck disable=SC2086
     if __zfs_argument_chosen $list1
     then
         COMPREPLY=($(compgen -W "$list2 $extra" -- "$cur"))
@@ -193,9 +195,10 @@ __zfs_complete_multiple_options()
 {
     local options=$1
     local cur=$2
+    local existing_opts
 
     COMPREPLY=($(compgen -W "$options" -- "${cur##*,}"))
-    local existing_opts=$(expr "$cur" : '\(.*,\)')
+    existing_opts=$(expr "$cur" : '\(.*,\)')
     if [[ $existing_opts ]]
     then
         COMPREPLY=( "${COMPREPLY[@]/#/${existing_opts}}" )
@@ -290,6 +293,7 @@ __zfs_complete()
                 *)
                     if ! __zfs_complete_switch "H,r,p,d,o,t,s"
                     then
+                        # shellcheck disable=SC2046
                         if __zfs_argument_chosen $(__zfs_get_properties)
                         then
                             COMPREPLY=($(compgen -W "$(__zfs_match_snapshot)" -- "$cur"))
@@ -303,7 +307,7 @@ __zfs_complete()
         inherit)
             if ! __zfs_complete_switch "r"
             then
-                __zfs_complete_ordered_arguments "$(__zfs_get_inheritable_properties)" "$(__zfs_match_snapshot)" $cur
+                __zfs_complete_ordered_arguments "$(__zfs_get_inheritable_properties)" "$(__zfs_match_snapshot)" "$cur"
             fi
             ;;
         list)
@@ -369,7 +373,7 @@ __zfs_complete()
             esac
             ;;
         set)
-            __zfs_complete_ordered_arguments "$(__zfs_get_editable_properties)" "$(__zfs_match_snapshot)" $cur
+            __zfs_complete_ordered_arguments "$(__zfs_get_editable_properties)" "$(__zfs_match_snapshot)" "$cur"
             __zfs_complete_nospace
             ;;
         upgrade)
@@ -388,7 +392,7 @@ __zfs_complete()
         destroy)
             if ! __zfs_complete_switch "d,f,n,p,R,r,v"
             then
-                __zfs_complete_multiple_options "$(__zfs_match_multiple_snapshots)" $cur
+                __zfs_complete_multiple_options "$(__zfs_match_multiple_snapshots)" "$cur"
                 __zfs_complete_nospace
             fi
             ;;
@@ -425,7 +429,7 @@ __zpool_list_pools()
 
 __zpool_complete()
 {
-    local cur prev cmd cmds
+    local cur prev cmd cmds pools
     COMPREPLY=()
     cur="${COMP_WORDS[COMP_CWORD]}"
     prev="${COMP_WORDS[COMP_CWORD-1]}"
@@ -440,7 +444,7 @@ __zpool_complete()
 
     case "${cmd}" in
         get)
-            __zfs_complete_ordered_arguments "$(__zpool_get_properties)" "$(__zpool_list_pools)" $cur
+            __zfs_complete_ordered_arguments "$(__zpool_get_properties)" "$(__zpool_list_pools)" "$cur"
             return 0
             ;;
         import)
@@ -453,12 +457,13 @@ __zpool_complete()
             return 0
             ;;
         set)
-            __zfs_complete_ordered_arguments "$(__zpool_get_editable_properties)" "$(__zpool_list_pools)" $cur
+            __zfs_complete_ordered_arguments "$(__zpool_get_editable_properties)" "$(__zpool_list_pools)" "$cur"
             __zfs_complete_nospace
             return 0
             ;;
         add|attach|clear|create|detach|offline|online|remove|replace)
-            local pools="$(__zpool_list_pools)"
+            pools="$(__zpool_list_pools)"
+            # shellcheck disable=SC2086
             if __zfs_argument_chosen $pools
             then
                 _filedir
diff --git a/contrib/bpftrace/Makefile.am b/contrib/bpftrace/Makefile.am
index 327bc6442..05e4f1c50 100644
--- a/contrib/bpftrace/Makefile.am
+++ b/contrib/bpftrace/Makefile.am
@@ -1,3 +1,7 @@
+include $(top_srcdir)/config/Shellcheck.am
+
 EXTRA_DIST = \
 	taskqlatency.bt \
 	zfs-trace.sh
+
+SHELLCHECKSCRIPTS = zfs-trace.sh
diff --git a/contrib/dracut/02zfsexpandknowledge/Makefile.am b/contrib/dracut/02zfsexpandknowledge/Makefile.am
index d31d389a0..b1bbb6bd3 100644
--- a/contrib/dracut/02zfsexpandknowledge/Makefile.am
+++ b/contrib/dracut/02zfsexpandknowledge/Makefile.am
@@ -1,4 +1,5 @@
 include $(top_srcdir)/config/Substfiles.am
+include $(top_srcdir)/config/Shellcheck.am
 
 pkgdracutdir = $(dracutdir)/modules.d/02zfsexpandknowledge
 pkgdracut_SCRIPTS = \
diff --git a/contrib/dracut/90zfs/Makefile.am b/contrib/dracut/90zfs/Makefile.am
index a4843827e..19b206ddd 100644
--- a/contrib/dracut/90zfs/Makefile.am
+++ b/contrib/dracut/90zfs/Makefile.am
@@ -1,4 +1,5 @@
 include $(top_srcdir)/config/Substfiles.am
+include $(top_srcdir)/config/Shellcheck.am
 
 pkgdracutdir = $(dracutdir)/modules.d/90zfs
 pkgdracut_SCRIPTS = \
diff --git a/contrib/dracut/Makefile.am b/contrib/dracut/Makefile.am
index 1065e5e94..8c9a6be08 100644
--- a/contrib/dracut/Makefile.am
+++ b/contrib/dracut/Makefile.am
@@ -1,3 +1,6 @@
+include $(top_srcdir)/config/Shellcheck.am
+
 SUBDIRS = 02zfsexpandknowledge 90zfs
+SHELLCHECKDIRS = $(SUBDIRS)
 
 EXTRA_DIST = README.dracut.markdown
diff --git a/contrib/initramfs/Makefile.am b/contrib/initramfs/Makefile.am
index 5eac6e215..931ceb131 100644
--- a/contrib/initramfs/Makefile.am
+++ b/contrib/initramfs/Makefile.am
@@ -1,9 +1,12 @@
+include $(top_srcdir)/config/Shellcheck.am
+
 initrddir = /usr/share/initramfs-tools
 
 dist_initrd_SCRIPTS = \
        zfsunlock
 
 SUBDIRS = conf.d conf-hooks.d hooks scripts
+SHELLCHECKDIRS = hooks scripts
 
 EXTRA_DIST = \
 	README.initramfs.markdown
diff --git a/contrib/initramfs/hooks/Makefile.am b/contrib/initramfs/hooks/Makefile.am
index f303e995b..0cd1aafcd 100644
--- a/contrib/initramfs/hooks/Makefile.am
+++ b/contrib/initramfs/hooks/Makefile.am
@@ -1,4 +1,5 @@
 include $(top_srcdir)/config/Substfiles.am
+include $(top_srcdir)/config/Shellcheck.am
 
 hooksdir = /usr/share/initramfs-tools/hooks
 
diff --git a/contrib/initramfs/scripts/Makefile.am b/contrib/initramfs/scripts/Makefile.am
index 2a142096e..444a5f374 100644
--- a/contrib/initramfs/scripts/Makefile.am
+++ b/contrib/initramfs/scripts/Makefile.am
@@ -1,6 +1,11 @@
+include $(top_srcdir)/config/Shellcheck.am
+
 scriptsdir = /usr/share/initramfs-tools/scripts
 
-dist_scripts_DATA = \
+dist_scripts_SCRIPTS = \
 	zfs
 
 SUBDIRS = local-top
+
+SHELLCHECKDIRS = $(SUBDIRS)
+SHELLCHECK_SHELL = sh
diff --git a/contrib/initramfs/scripts/local-top/Makefile.am b/contrib/initramfs/scripts/local-top/Makefile.am
index 1523a907c..897f9b2e2 100644
--- a/contrib/initramfs/scripts/local-top/Makefile.am
+++ b/contrib/initramfs/scripts/local-top/Makefile.am
@@ -1,3 +1,5 @@
+include $(top_srcdir)/config/Shellcheck.am
+
 localtopdir = /usr/share/initramfs-tools/scripts/local-top
 
 dist_localtop_SCRIPTS = \
diff --git a/contrib/initramfs/scripts/zfs b/contrib/initramfs/scripts/zfs
index a125d71e7..bb7bbb34e 100644
--- a/contrib/initramfs/scripts/zfs
+++ b/contrib/initramfs/scripts/zfs
@@ -5,6 +5,8 @@
 #
 # Enable this by passing boot=zfs on the kernel command line.
 #
+# $quiet, $root, $rpool, $bootfs come from the cmdline:
+# shellcheck disable=SC2154
 
 # Source the common functions
 . /etc/zfs/zfs-functions
@@ -102,14 +104,10 @@ find_rootfs()
 # Support function to get a list of all pools, separated with ';'
 find_pools()
 {
-	CMD="$*"
-
-	pools=$($CMD 2> /dev/null | \
+	pools=$("$@" 2> /dev/null | \
 		grep -E "pool:|^[a-zA-Z0-9]" | \
 		sed 's@.*: @@' | \
-		while read -r pool; do \
-		    printf "%s" "$pool;"
-		done)
+		tr '\n' ';')
 
 	echo "${pools%%;}" # Return without the last ';'.
 }
@@ -203,7 +201,7 @@ import_pool()
 	# exists).
 	if [ -n "$USE_DISK_BY_ID" ] && [ -z "$ZPOOL_IMPORT_PATH" ]
 	then
-		dirs="$(for dir in $(echo /dev/disk/by-*)
+		dirs="$(for dir in /dev/disk/by-*
 		do
 			# Ignore by-vdev here - we want it first!
 			echo "$dir" | grep -q /by-vdev && continue
@@ -329,6 +327,7 @@ mount_fs()
 
 	# Need the _original_ datasets mountpoint!
 	mountpoint=$(get_fs_value "$fs" mountpoint)
+	ZFS_CMD="mount -o zfsutil -t zfs"
 	if [ "$mountpoint" = "legacy" ] || [ "$mountpoint" = "none" ]; then
 		# Can't use the mountpoint property. Might be one of our
 		# clones. Check the 'org.zol:mountpoint' property set in
@@ -348,15 +347,11 @@ mount_fs()
 			fi
 		fi
 
+		# If it's not a legacy filesystem, it can only be a
+		# native one...
 		if [ "$mountpoint" = "legacy" ]; then
 			ZFS_CMD="mount -t zfs"
-		else
-			# If it's not a legacy filesystem, it can only be a
-			# native one...
-			ZFS_CMD="mount -o zfsutil -t zfs"
 		fi
-	else
-		ZFS_CMD="mount -o zfsutil -t zfs"
 	fi
 
 	# Possibly decrypt a filesystem using native encryption.
@@ -556,7 +551,6 @@ rollback_snap()
 ask_user_snap()
 {
 	fs="$1"
-	i=1
 
 	# We need to temporarily disable debugging. Set 'debug' so we
 	# remember to enabled it again.
@@ -569,16 +563,25 @@ ask_user_snap()
 	# Because we need the resulting snapshot, which is sent on
 	# stdout to the caller, we use stderr for our questions.
 	echo "What snapshot do you want to boot from?" > /dev/stderr
-	while read -r snap; do
-	    echo "  $i: ${snap}" > /dev/stderr
-	    eval "$(echo SNAP_$i=$snap)"
-	    i=$((i + 1))
-	done <<EOT
-$("${ZFS}" list -H -oname -tsnapshot -r "${fs}")
-EOT
+	# shellcheck disable=SC2046
+	IFS="
+" set -- $("${ZFS}" list -H -oname -tsnapshot -r "${fs}")
 
-	echo "%s" "  Snap nr [1-$((i-1))]? " > /dev/stderr
-	read -r snapnr
+	i=1
+	for snap in "$@"; do
+		echo "  $i: $snap"
+		i=$((i + 1))
+	done > /dev/stderr
+
+	# expr instead of test here because [ a -lt 0 ] errors out,
+	# but expr falls back to lexicographical, which works out right
+	snapnr=0
+	while expr "$snapnr" "<" 1 > /dev/null ||
+	    expr "$snapnr" ">" "$#" > /dev/null
+	do
+		printf "%s" "Snap nr [1-$#]? " > /dev/stderr
+		read -r snapnr
+	done
 
 	# Re-enable debugging.
 	if [ -n "${debug}" ]; then
@@ -586,7 +589,7 @@ EOT
 		set -x
 	fi
 
-	echo "$(eval echo '$SNAP_'$snapnr)"
+	eval echo '$'"$snapnr"
 }
 
 setup_snapshot_booting()
@@ -706,7 +709,7 @@ mountroot()
 
 	# ------------
 	# Look for the cache file (if any).
-	[ ! -f ${ZPOOL_CACHE} ] && unset ZPOOL_CACHE
+	[ ! -f "${ZPOOL_CACHE}" ] && unset ZPOOL_CACHE
 
 	# ------------
 	# Compatibility: 'ROOT' is for Debian GNU/Linux (etc),
@@ -796,7 +799,8 @@ mountroot()
 		#
 		# Reassign the variable by dumping the environment and
 		# stripping the zfs-bootfs= prefix.  Let the shell handle
-		# quoting through the eval command.
+		# quoting through the eval command:
+		# shellcheck disable=SC2046
 		eval ZFS_RPOOL=$(set | sed -n -e 's,^zfs-bootfs=,,p')
 	fi
 
@@ -950,7 +954,7 @@ mountroot()
 
 	touch /run/zfs_unlock_complete
 	if [ -e /run/zfs_unlock_complete_notify ]; then
-		read -r zfs_unlock_complete_notify < /run/zfs_unlock_complete_notify
+		read -r < /run/zfs_unlock_complete_notify
 	fi
 
 	# ------------
diff --git a/etc/Makefile.am b/etc/Makefile.am
index ac71da944..aa9ff182c 100644
--- a/etc/Makefile.am
+++ b/etc/Makefile.am
@@ -1,5 +1,9 @@
+include $(top_srcdir)/config/Shellcheck.am
+
 SUBDIRS = zfs sudoers.d
+SHELLCHECKDIRS = zfs
 if BUILD_LINUX
+SHELLCHECKDIRS += default $(ZFS_INIT_SYSV)
 SUBDIRS += default $(ZFS_INIT_SYSTEMD) $(ZFS_INIT_SYSV) $(ZFS_MODULE_LOAD)
 endif
 DIST_SUBDIRS = default init.d zfs systemd modules-load.d sudoers.d
diff --git a/etc/default/Makefile.am b/etc/default/Makefile.am
index 0ec868e13..b88eb5494 100644
--- a/etc/default/Makefile.am
+++ b/etc/default/Makefile.am
@@ -1,5 +1,9 @@
 include $(top_srcdir)/config/Substfiles.am
+include $(top_srcdir)/config/Shellcheck.am
 
 initconf_SCRIPTS = zfs
 
 SUBSTFILES += $(initconf_SCRIPTS)
+
+SHELLCHECK_SHELL = sh
+SHELLCHECK_IGNORE = ,SC2034
diff --git a/etc/init.d/Makefile.am b/etc/init.d/Makefile.am
index 9285a995a..f93af1fd7 100644
--- a/etc/init.d/Makefile.am
+++ b/etc/init.d/Makefile.am
@@ -1,7 +1,10 @@
 include $(top_srcdir)/config/Substfiles.am
+include $(top_srcdir)/config/Shellcheck.am
 
 EXTRA_DIST += README.md
 
 init_SCRIPTS = zfs-import zfs-mount zfs-share zfs-zed
 
 SUBSTFILES += $(init_SCRIPTS)
+
+SHELLCHECK_SHELL = dash # local variables
diff --git a/etc/init.d/zfs-import.in b/etc/init.d/zfs-import.in
index 6b1b2f243..e4bc7b833 100755
--- a/etc/init.d/zfs-import.in
+++ b/etc/init.d/zfs-import.in
@@ -72,6 +72,7 @@ do_import_all_visible()
 	local exception dir ZPOOL_IMPORT_PATH RET=0 r=1
 
 	# In case not shutdown cleanly.
+	# shellcheck disable=SC2154
 	[ -n "$init" ] && rm -f /etc/dfs/sharetab
 
 	# Just simplify code later on.
@@ -157,7 +158,7 @@ do_import_all_visible()
 			echo "$dir" | grep -q /by-vdev && continue
 			[ ! -d "$dir" ] && continue
 
-			echo -n "$dir:"
+			printf "%s" "$dir:"
 		done | sed 's,:$,,g')"
 
 		if [ -d "/dev/disk/by-vdev" ]
@@ -214,6 +215,7 @@ do_import_all_visible()
 		# Import by using ZPOOL_IMPORT_PATH (either set above or in
 		# the config file) _or_ with the 'built in' default search
 		# paths. This is the preferred way.
+		# shellcheck disable=SC2086
 		"$ZPOOL" import -N ${ZPOOL_IMPORT_OPTS} "$pool" 2> /dev/null
 		r="$?" ; RET=$((RET + r))
 		if [ "$r" -eq 0 ]
@@ -235,6 +237,7 @@ do_import_all_visible()
 				zfs_log_progress_msg " using cache file"
 			fi
 
+			# shellcheck disable=SC2086
 			"$ZPOOL" import -c "$ZPOOL_CACHE" -N ${ZPOOL_IMPORT_OPTS} \
 				"$pool" 2> /dev/null
 			r="$?" ; RET=$((RET + r))
diff --git a/etc/init.d/zfs-mount.in b/etc/init.d/zfs-mount.in
index cb571faf9..000619b67 100755
--- a/etc/init.d/zfs-mount.in
+++ b/etc/init.d/zfs-mount.in
@@ -80,11 +80,11 @@ do_mount()
 
 	read_mtab  "^/dev/(zd|zvol)"
 	read_fstab "^/dev/(zd|zvol)"
-	i=0; var=$(eval echo "FSTAB_$i")
-	while [ -n "$(eval echo "$""$var")" ]
+	i=0; var="FSTAB_0"
+	while [ -n "$(eval echo "\$$var")" ]
 	do
-		mntpt=$(eval echo "$""$var")
-		dev=$(eval echo "$"FSTAB_dev_$i)
+		mntpt=$(eval echo "\$$var")
+		dev=$(eval echo "\$FSTAB_dev_$i")
 		if ! in_mtab "$mntpt" && ! is_mounted "$mntpt" && [ -e "$dev" ]
 		then
 			check_boolean "$VERBOSE_MOUNT" && \
@@ -93,15 +93,15 @@ do_mount()
 		fi
 
 		i=$((i + 1))
-		var=$(eval echo FSTAB_$i)
+		var=$(eval echo "FSTAB_$i")
 	done
 
 	read_mtab  "[[:space:]]zfs[[:space:]]"
 	read_fstab "[[:space:]]zfs[[:space:]]"
-	i=0; var=$(eval echo FSTAB_$i)
-	while [ -n "$(eval echo "$""$var")" ]
+	i=0; var=$(eval echo "FSTAB_$i")
+	while [ -n "$(eval echo "\$$var")" ]
 	do
-		mntpt=$(eval echo "$""$var")
+		mntpt=$(eval echo "\$$var")
 		if ! in_mtab "$mntpt" && ! is_mounted "$mntpt"
 		then
 			check_boolean "$VERBOSE_MOUNT" && \
@@ -110,7 +110,7 @@ do_mount()
 		fi
 
 		i=$((i + 1))
-		var=$(eval echo FSTAB_$i)
+		var=$(eval echo "FSTAB_$i")
 	done
 	check_boolean "$VERBOSE_MOUNT" && zfs_log_end_msg 0
 
@@ -133,11 +133,11 @@ do_unmount()
 
 	read_mtab  "^/dev/(zd|zvol)"
 	read_fstab "^/dev/(zd|zvol)"
-	i=0; var=$(eval echo FSTAB_$i)
-	while [ -n "$(eval echo "$""$var")" ]
+	i=0; var="FSTAB_0"
+	while [ -n "$(eval echo "\$$var")" ]
 	do
-		mntpt=$(eval echo "$""$var")
-		dev=$(eval echo "$"FSTAB_dev_$i)
+		mntpt=$(eval echo "\$$var")
+		dev=$(eval echo "\$FSTAB_dev_$i")
 		if in_mtab "$mntpt"
 		then
 			check_boolean "$VERBOSE_MOUNT" && \
@@ -146,15 +146,15 @@ do_unmount()
 		fi
 
 		i=$((i + 1))
-		var=$(eval echo FSTAB_$i)
+		var=$(eval echo "FSTAB_$i")
 	done
 
 	read_mtab  "[[:space:]]zfs[[:space:]]"
 	read_fstab "[[:space:]]zfs[[:space:]]"
-	i=0; var=$(eval echo FSTAB_$i)
-	while [ -n "$(eval echo "$""$var")" ]
+	i=0; var="FSTAB_0"
+	while [ -n "$(eval echo "\$$var")" ]
 	do
-		mntpt=$(eval echo "$""$var")
+		mntpt=$(eval echo "\$$var")
 		if in_mtab "$mntpt"; then
 			check_boolean "$VERBOSE_MOUNT" && \
 			    zfs_log_progress_msg "$mntpt "
@@ -162,7 +162,7 @@ do_unmount()
 		fi
 
 		i=$((i + 1))
-		var=$(eval echo FSTAB_$i)
+		var=$(eval echo "FSTAB_$i")
 	done
 	check_boolean "$VERBOSE_MOUNT" && zfs_log_end_msg 0
 
diff --git a/etc/init.d/zfs-zed.in b/etc/init.d/zfs-zed.in
index e5550e500..e5256cbc6 100755
--- a/etc/init.d/zfs-zed.in
+++ b/etc/init.d/zfs-zed.in
@@ -30,6 +30,7 @@
 ZED_NAME="zed"
 ZED_PIDFILE="@runstatedir@/$ZED_NAME.pid"
 
+# shellcheck disable=SC2034
 extra_started_commands="reload"
 
 # Exit if the package is not installed
diff --git a/etc/systemd/Makefile.am b/etc/systemd/Makefile.am
index 7b47b93fc..66232a5ff 100644
--- a/etc/systemd/Makefile.am
+++ b/etc/systemd/Makefile.am
@@ -1 +1,4 @@
+include $(top_srcdir)/config/Shellcheck.am
+
 SUBDIRS = system system-generators
+SHELLCHECKDIRS = system-generators
diff --git a/etc/zfs/Makefile.am b/etc/zfs/Makefile.am
index b9123c176..3dee81c75 100644
--- a/etc/zfs/Makefile.am
+++ b/etc/zfs/Makefile.am
@@ -1,4 +1,5 @@
 include $(top_srcdir)/config/Substfiles.am
+include $(top_srcdir)/config/Shellcheck.am
 
 pkgsysconfdir = $(sysconfdir)/zfs
 
@@ -13,3 +14,5 @@ pkgsysconf_SCRIPTS = \
 	zfs-functions
 
 SUBSTFILES += $(pkgsysconf_SCRIPTS)
+
+SHELLCHECK_SHELL = dash # local variables
diff --git a/etc/zfs/zfs-functions.in b/etc/zfs/zfs-functions.in
index a07cce60d..2fb065afd 100644
--- a/etc/zfs/zfs-functions.in
+++ b/etc/zfs/zfs-functions.in
@@ -44,7 +44,7 @@ elif type success > /dev/null 2>&1 ; then
 		fi
 	}
 
-	zfs_log_begin_msg() { echo -n "$1 "; }
+	zfs_log_begin_msg() { printf "%s" "$1 "; }
 	zfs_log_end_msg() {
 		zfs_set_ifs "$OLD_IFS"
 		if [ "$1" -eq 0 ]; then
@@ -61,17 +61,17 @@ elif type success > /dev/null 2>&1 ; then
 		echo
 		zfs_set_ifs "$TMP_IFS"
 	}
-	zfs_log_progress_msg() { echo -n "$""$1"; }
+	zfs_log_progress_msg() { printf "%s" "$""$1"; }
 elif type einfo > /dev/null 2>&1 ; then
 	# Gentoo functions
 	zfs_log_begin_msg() { ebegin "$1"; }
 	zfs_log_end_msg() { eend "$1"; }
 	zfs_log_failure_msg() { eend "$1"; }
-#	zfs_log_progress_msg() { echo -n "$1"; }
-	zfs_log_progress_msg() { echo -n; }
+#	zfs_log_progress_msg() { printf "%s" "$1"; }
+	zfs_log_progress_msg() { :; }
 else
 	# Unknown - simple substitutes.
-	zfs_log_begin_msg() { echo -n "$1"; }
+	zfs_log_begin_msg() { printf "%s" "$1"; }
 	zfs_log_end_msg() {
 		ret=$1
 		if [ "$ret" -ge 1 ]; then
@@ -82,7 +82,7 @@ else
 		return "$ret"
 	}
 	zfs_log_failure_msg() { echo "$1"; }
-	zfs_log_progress_msg() { echo -n "$1"; }
+	zfs_log_progress_msg() { printf "%s" "$1"; }
 fi
 
 # Paths to what we need
@@ -134,15 +134,15 @@ zfs_daemon_start()
 {
 	local PIDFILE="$1";	shift
 	local DAEMON_BIN="$1";	shift
-	local DAEMON_ARGS="$*"
 
 	if type start-stop-daemon > /dev/null 2>&1 ; then
 		# LSB functions
 		start-stop-daemon --start --quiet --pidfile "$PIDFILE" \
 		    --exec "$DAEMON_BIN" --test > /dev/null || return 1
 
-	        start-stop-daemon --start --quiet --exec "$DAEMON_BIN" -- \
-		    $DAEMON_ARGS || return 2
+		# shellcheck disable=SC2086
+		start-stop-daemon --start --quiet --exec "$DAEMON_BIN" -- \
+		    "$@" || return 2
 
 		# On Debian, there's a 'sendsigs' script that will
 		# kill basically everything quite early and zed is stopped
@@ -153,8 +153,9 @@ zfs_daemon_start()
 			ln -sf "$PIDFILE" /run/sendsigs.omit.d/zed
 		fi
 	elif type daemon > /dev/null 2>&1 ; then
-	        # Fedora/RedHat functions
-		daemon --pidfile "$PIDFILE" "$DAEMON_BIN" $DAEMON_ARGS
+		# Fedora/RedHat functions
+		# shellcheck disable=SC2086
+		daemon --pidfile "$PIDFILE" "$DAEMON_BIN" "$@"
 		return $?
 	else
 		# Unsupported
@@ -234,7 +235,7 @@ zfs_daemon_reload()
 		return $?
 	elif type killproc > /dev/null 2>&1 ; then
 		# Fedora/RedHat functions
-                killproc -p "$PIDFILE" "$DAEMON_NAME" -HUP
+		killproc -p "$PIDFILE" "$DAEMON_NAME" -HUP
 		return $?
 	else
 		# Unsupported
@@ -287,6 +288,7 @@ checksystem()
 		# HOWEVER, only do this if we're called at the boot up
 		# (from init), not if we're running interactively (as in
 		# from the shell - we know what we're doing).
+		# shellcheck disable=SC2154
 		[ -n "$init" ] && exit 3
 	fi
 
@@ -301,6 +303,7 @@ checksystem()
 
 get_root_pool()
 {
+	# shellcheck disable=SC2046
 	set -- $(mount | grep ' on / ')
 	[ "$5" = "zfs" ] && echo "${1%%/*}"
 }
@@ -338,9 +341,10 @@ load_module()
 read_mtab()
 {
 	local match="$1"
-	local fs mntpnt fstype opts rest TMPFILE
+	local fs mntpnt fstype opts rest
 
 	# Unset all MTAB_* variables
+	# shellcheck disable=SC2046
 	unset $(env | grep ^MTAB_ | sed 's,=.*,,')
 
 	while read -r fs mntpnt fstype opts rest; do
@@ -352,8 +356,8 @@ read_mtab()
 			# * We need to use the external echo, because the
 			#   internal one would interpret the backslash code
 			#   (incorrectly), giving us a 
 instead.
-			mntpnt=$(/bin/echo "$mntpnt" | sed "s,\\\0,\\\00,g")
-			fs=$(/bin/echo "$fs" | sed "s,\\\0,\\\00,")
+			mntpnt=$(/bin/echo "$mntpnt" | sed 's,\\0,\\00,g')
+			fs=$(/bin/echo "$fs" | sed 's,\\0,\\00,')
 
 			# Remove 'unwanted' characters.
 			mntpnt=$(printf '%b\n' "$mntpnt" | sed -e 's,/,,g' \
@@ -386,6 +390,7 @@ read_fstab()
 	local i var
 
 	# Unset all FSTAB_* variables
+	# shellcheck disable=SC2046
 	unset $(env | grep ^FSTAB_ | sed 's,=.*,,')
 
 	i=0
diff --git a/scripts/Makefile.am b/scripts/Makefile.am
index f59826fe6..f338cdc39 100644
--- a/scripts/Makefile.am
+++ b/scripts/Makefile.am
@@ -1,3 +1,5 @@
+include $(top_srcdir)/config/Shellcheck.am
+
 pkgdatadir = $(datadir)/@PACKAGE@
 
 dist_pkgdata_SCRIPTS = \
@@ -7,19 +9,25 @@ dist_pkgdata_SCRIPTS = \
 	zloop.sh \
 	zfs-helpers.sh
 
-EXTRA_DIST = \
+EXTRA_SCRIPTS = \
 	commitcheck.sh \
 	common.sh.in \
-	cstyle.pl \
 	dkms.mkconf \
 	dkms.postbuild \
-	enum-extract.pl \
 	kmodtool \
 	make_gitrev.sh \
 	man-dates.sh \
-	paxcheck.sh \
+	paxcheck.sh
+
+EXTRA_DIST = \
+	cstyle.pl \
+	enum-extract.pl \
 	zfs2zol-patch.sed \
-	zol2zfs-patch.sed
+	zol2zfs-patch.sed \
+	$(EXTRA_SCRIPTS)
+
+SHELLCHECK_IGNORE = ,SC1117
+SHELLCHECKSCRIPTS = $(EXTRA_SCRIPTS)
 
 define EXTRA_ENVIRONMENT
 
diff --git a/scripts/dkms.mkconf b/scripts/dkms.mkconf
index 8649b9318..9d12a8c3b 100755
--- a/scripts/dkms.mkconf
+++ b/scripts/dkms.mkconf
@@ -6,19 +6,21 @@ pkgcfg=/etc/sysconfig/zfs
 
 while getopts "n:v:c:f:" opt; do
 	case $opt in
-		n) pkgname=$OPTARG ;;
-		v) pkgver=$OPTARG  ;;
-		c) pkgcfg=$OPTARG ;;
+		n) pkgname=$OPTARG  ;;
+		v) pkgver=$OPTARG   ;;
+		c) pkgcfg=$OPTARG   ;;
 		f) filename=$OPTARG ;;
+    *) err=1            ;;
 	esac
 done
 
-if [ -z "${pkgname}" ] || [ -z "${pkgver}" ] || [ -z "${filename}" ]; then
+if [ -z "${pkgname}" ] || [ -z "${pkgver}" ] || [ -z "${filename}" ] ||
+    [ -n "${err}" ]; then
 	echo "Usage: $PROG -n <pkgname> -v <pkgver> -c <pkgcfg> -f <filename>"
 	exit 1
 fi
 
-cat >${filename} <<EOF
+exec cat >"${filename}" <<EOF
 PACKAGE_NAME="${pkgname}"
 PACKAGE_VERSION="${pkgver}"
 PACKAGE_CONFIG="${pkgcfg}"
diff --git a/scripts/dkms.postbuild b/scripts/dkms.postbuild
index 81de47587..a2ceff64a 100755
--- a/scripts/dkms.postbuild
+++ b/scripts/dkms.postbuild
@@ -9,16 +9,17 @@ while getopts "a:k:n:t:v:" opt; do
 		n) pkgname=$OPTARG ;;
 		t) tree=$OPTARG    ;;
 		v) pkgver=$OPTARG  ;;
+		*) err=1           ;;
 	esac
 done
 
 if [ -z "${arch}" ] || [ -z "${kver}" ] || [ -z "${pkgname}" ] || \
-    [ -z "${tree}" ] || [ -z "${pkgver}" ]; then
+    [ -z "${tree}" ] || [ -z "${pkgver}" ] || [ -n "${err}" ]; then
 	echo "Usage: $PROG -a <arch> -k <kver> -n <pkgname>" \
-	     "-t <tree> -v <pkgver>"
+	    "-t <tree> -v <pkgver>"
 	exit 1
 fi
 
-cp "${tree}/${pkgname}/${pkgver}/build/zfs_config.h"          \
+exec cp "${tree}/${pkgname}/${pkgver}/build/zfs_config.h"     \
    "${tree}/${pkgname}/${pkgver}/build/module/Module.symvers" \
    "${tree}/${pkgname}/${pkgver}/${kver}/${arch}/"
diff --git a/scripts/kmodtool b/scripts/kmodtool
index 35d54bad2..26bacf599 100755
--- a/scripts/kmodtool
+++ b/scripts/kmodtool
@@ -1,4 +1,5 @@
 #!/usr/bin/env bash
+# shellcheck disable=SC2086
 
 # kmodtool - Helper script for building kernel module RPMs
 # Copyright (c) 2003-2012 Ville Skyttä <[email protected]>,
@@ -38,15 +39,16 @@ prefix=
 filterfile=
 target=
 buildroot=
+dashvariant=
 
 error_out()
 {
 	local errorlevel=${1}
 	shift
-	echo "Error: $@" >&2
+	echo "Error: $*" >&2
 	# the next line is not multi-line safe -- not needed *yet*
-	echo "%global kmodtool_check echo \"kmodtool error: $@\"; exit ${errorlevel};"
-	exit ${errorlevel}
+	echo "%global kmodtool_check echo \"kmodtool error: $*\"; exit ${errorlevel};"
+	exit "${errorlevel}"
 }
 
 print_rpmtemplate_header()
@@ -579,7 +581,7 @@ elif [[ ! "${kmodname}" ]]; then
 		error_out 2 "please pass kmodname with --kmodname"
 elif [[ ! "${kernels_known_variants}" ]] ; then
 		error_out 2 "could not determine known variants"
-elif ( [[ "${obsolete_name}" ]] && [[ ! "${obsolete_version}" ]] ) ||  ( [[ ! "${obsolete_name}" ]] && [[ "${obsolete_version}" ]] ) ; then
+elif { [[ "${obsolete_name}" ]] && [[ ! "${obsolete_version}" ]]; } ||  { [[ ! "${obsolete_name}" ]] && [[ "${obsolete_version}" ]]; } ; then
 		error_out 2 "you need to provide both --obsolete-name and --obsolete-version"
 fi
 
@@ -597,7 +599,7 @@ else
 	# we need more sanity checks in this case
 	if [[ ! "${repo}" ]]; then
 		error_out 2 "please provide repo name with --repo"
-	elif ! $(which buildsys-build-${repo}-kerneldevpkgs &> /dev/null) ; then
+	elif ! command -v "buildsys-build-${repo}-kerneldevpkgs" &> /dev/null ; then
 		error_out 2 "buildsys-build-${repo}-kerneldevpkgs not found"
 	fi
 
@@ -611,7 +613,7 @@ else
 
 	kernel_versions_to_build_for="$(buildsys-build-${repo}-kerneldevpkgs --${build_kernels} ${cmdoptions})"
 	returncode=$?
-	if (( ${returncode} != 0 )); then
+	if (( returncode != 0 )); then
 		error_out 2 "buildsys-build-${repo}-kerneldevpkgs failed: $(buildsys-build-${repo}-kerneldevpkgs --${build_kernels} ${cmdoptions})"
 	fi
 
diff --git a/tests/Makefile.am b/tests/Makefile.am
index f13b19613..4bdde9c45 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -1,3 +1,8 @@
+include $(top_srcdir)/config/Shellcheck.am
+
 SUBDIRS = runfiles test-runner zfs-tests
 
 EXTRA_DIST = README.md
+
+SHELLCHECKSCRIPTS = $$(find -name '*.sh')
+.PHONY: $(SHELLCHECKSCRIPTS)
diff --git a/tests/zfs-tests/tests/perf/scripts/prefetch_io.sh b/tests/zfs-tests/tests/perf/scripts/prefetch_io.sh
index d8181f2e8..07688ef21 100755
--- a/tests/zfs-tests/tests/perf/scripts/prefetch_io.sh
+++ b/tests/zfs-tests/tests/perf/scripts/prefetch_io.sh
@@ -64,17 +64,17 @@ async_upgrade_sync=$(get_async_upgrade_sync)
 while true
 do
 	new_prefetch_ios=$(get_prefetch_ios)
-	printf "%u\n%-24s\t%u\n" "$(date +%s)" "prefetch_ios" \
+	printf '%u\n%-24s\t%u\n' "$(date +%s)" "prefetch_ios" \
 	    $(( new_prefetch_ios - prefetch_ios ))
 	prefetch_ios=$new_prefetch_ios
 
 	new_prefetched_demand_reads=$(get_prefetched_demand_reads)
-	printf "%-24s\t%u\n" "prefetched_demand_reads" \
+	printf '%-24s\t%u\n' "prefetched_demand_reads" \
 	    $(( new_prefetched_demand_reads - prefetched_demand_reads ))
 	prefetched_demand_reads=$new_prefetched_demand_reads
 
 	new_async_upgrade_sync=$(get_async_upgrade_sync)
-	printf "%-24s\t%u\n" "async_upgrade_sync" \
+	printf '%-24s\t%u\n' "async_upgrade_sync" \
 	    $(( new_async_upgrade_sync - async_upgrade_sync ))
 	async_upgrade_sync=$new_async_upgrade_sync