diff --git a/completion/available/crystal.completion.bash b/completion/available/crystal.completion.bash
index 7644ffd4d4..25dd496c01 100644
--- a/completion/available/crystal.completion.bash
+++ b/completion/available/crystal.completion.bash
@@ -1 +1,2 @@
+# shellcheck shell=bash
 _log_warning 'Bash completion for "crystal" is now covered by "system". This completion can be disabled.'
diff --git a/completion/available/defaults.completion.bash b/completion/available/defaults.completion.bash
index 39d7ea95b0..0baee19679 100644
--- a/completion/available/defaults.completion.bash
+++ b/completion/available/defaults.completion.bash
@@ -1,4 +1,5 @@
 # shellcheck shell=bash
+# shellcheck disable=SC1090
 
 if test -s "${BASH_IT?}/vendor/github.com/gaelicWizard/bash-progcomp/defaults.completion.bash"; then
 	source "$_"
diff --git a/completion/available/drush.completion.bash b/completion/available/drush.completion.bash
index 6628c65513..ccee2c3edf 100644
--- a/completion/available/drush.completion.bash
+++ b/completion/available/drush.completion.bash
@@ -1,2 +1,3 @@
+# shellcheck shell=bash
 _log_warning 'Bash completion for "drush" is now deprecated, as it used code with incompatible license.
 Please disable this completion and use the instructions from "drush" developers instead.'
diff --git a/completion/available/fabric.completion.bash b/completion/available/fabric.completion.bash
index 163a479b80..717fb4badd 100644
--- a/completion/available/fabric.completion.bash
+++ b/completion/available/fabric.completion.bash
@@ -41,10 +41,10 @@ export FAB_COMPLETION_CACHED_TASKS_FILENAME=".fab_tasks~"
 # Set command to get time of last file modification as seconds since Epoch
 case "$OSTYPE" in
 	'darwin'* | 'freebsd'*)
-		__FAB_COMPLETION_MTIME_COMMAND="stat -f '%m'"
+		__FAB_COMPLETION_MTIME_COMMAND=(stat -f '%m')
 		;;
 	*)
-		__FAB_COMPLETION_MTIME_COMMAND="stat -c '%Y'"
+		__FAB_COMPLETION_MTIME_COMMAND=(stat -c '%Y')
 		;;
 esac
 
@@ -52,7 +52,7 @@ esac
 # Get time of last fab cache file modification as seconds since Epoch
 #
 function __fab_chache_mtime() {
-	${__FAB_COMPLETION_MTIME_COMMAND} \
+	"${__FAB_COMPLETION_MTIME_COMMAND[@]}" \
 		$FAB_COMPLETION_CACHED_TASKS_FILENAME | xargs -n 1 expr
 }
 
@@ -62,10 +62,11 @@ function __fab_chache_mtime() {
 function __fab_fabfile_mtime() {
 	local f="fabfile"
 	if [[ -e "$f.py" ]]; then
-		${__FAB_COMPLETION_MTIME_COMMAND} "$f.py" | xargs -n 1 expr
+		"${__FAB_COMPLETION_MTIME_COMMAND[@]}" "$f.py" | xargs -n 1 expr
 	else
 		# Suppose that it's a fabfile dir
-		find $f/*.py -exec ${__FAB_COMPLETION_MTIME_COMMAND} {} + \
+		# shellcheck disable=SC2038
+		find "$f"/*.py -exec "${__FAB_COMPLETION_MTIME_COMMAND[@]}" {} + \
 			| xargs -n 1 expr | sort -n -r | head -1
 	fi
 }
@@ -79,15 +80,16 @@ function __fab_completion() {
 
 	# Variables to hold the current word and possible matches
 	local cur="${COMP_WORDS[COMP_CWORD]}"
-	local opts=()
+	local opts
 
 	# Generate possible matches and store them in variable "opts"
 	case "${cur}" in
 		-*)
 			if [[ -z "${__FAB_COMPLETION_LONG_OPT}" ]]; then
-				export __FAB_COMPLETION_LONG_OPT=$(
+				__FAB_COMPLETION_LONG_OPT=$(
 					fab --help | grep -E -o "\-\-[A-Za-z_\-]+\=?" | sort -u
 				)
+				export __FAB_COMPLETION_LONG_OPT
 			fi
 			opts="${__FAB_COMPLETION_LONG_OPT}"
 			;;
@@ -124,6 +126,7 @@ function __fab_completion() {
 	esac
 
 	# Set possible completions
-	COMPREPLY=($(compgen -W "${opts}" -- ${cur}))
+	COMPREPLY=()
+	while IFS='' read -r line; do COMPREPLY+=("$line"); done < <(compgen -W "${opts}" -- "${cur}")
 }
 complete -o default -o nospace -F __fab_completion fab
diff --git a/completion/available/gradle.completion.bash b/completion/available/gradle.completion.bash
index cedf15dc71..9b9072c17d 100644
--- a/completion/available/gradle.completion.bash
+++ b/completion/available/gradle.completion.bash
@@ -22,7 +22,7 @@
 
 # Bash breaks words on : by default. Subproject tasks have ':'
 # Avoid inaccurate completions for subproject tasks
-COMP_WORDBREAKS=$(echo "$COMP_WORDBREAKS" | sed -e 's/://g')
+COMP_WORDBREAKS="${COMP_WORDBREAKS//:/}"
 
 function __gradle-set-project-root-dir() {
 	project_root_dir="$(_bash-it-find-in-ancestor "settings.gradle" "gradlew")"
@@ -31,7 +31,7 @@ function __gradle-set-project-root-dir() {
 
 __gradle-init-cache-dir() {
 	cache_dir="$HOME/.gradle/completion"
-	mkdir -p $cache_dir
+	mkdir -p "$cache_dir"
 }
 
 __gradle-set-build-file() {
@@ -39,7 +39,8 @@ __gradle-set-build-file() {
 	# Otherwise, default is the file 'build.gradle' in the current directory.
 	gradle_build_file="$project_root_dir/build.gradle"
 	if [[ -f "$project_root_dir/settings.gradle" ]]; then
-		local build_file_name=$(grep "^rootProject\.buildFileName" "$project_root_dir/settings.gradle" \
+		local build_file_name
+		build_file_name=$(grep "^rootProject\.buildFileName" "$project_root_dir/settings.gradle" \
 			| sed -n -e "s/rootProject\.buildFileName = [\'\"]\(.*\)[\'\"]/\1/p")
 		gradle_build_file="$project_root_dir/${build_file_name:-build.gradle}"
 	fi
@@ -47,15 +48,15 @@ __gradle-set-build-file() {
 
 __gradle-set-cache-name() {
 	# Cache name is constructed from the absolute path of the build file.
-	cache_name=$(echo $gradle_build_file | sed -e 's/\//_/g')
+	cache_name=${gradle_build_file//'/'/_}
 }
 
 __gradle-set-files-checksum() {
 	# Cache MD5 sum of all Gradle scripts and modified timestamps
 	if _command_exists md5; then
-		gradle_files_checksum=$(md5 -q -s "$(cat "$cache_dir/$cache_name" | xargs ls -o 2> /dev/null)")
+		gradle_files_checksum=$(md5 -q -s "$(xargs ls -o < "$cache_dir/$cache_name" 2> /dev/null)")
 	elif _command_exists md5sum; then
-		gradle_files_checksum=$(cat "$cache_dir/$cache_name" | xargs ls -o 2> /dev/null | md5sum | awk '{print $1}')
+		gradle_files_checksum=$(xargs ls -o < "$cache_dir/$cache_name" 2> /dev/null | md5sum | awk '{print $1}')
 	else
 		echo "Cannot generate completions as neither md5 nor md5sum exist on \$PATH"
 	fi
@@ -66,10 +67,15 @@ __gradle-generate-script-cache() {
 	local cache_ttl_mins=${GRADLE_CACHE_TTL_MINUTES:-30240}
 	local script_exclude_pattern=${GRADLE_COMPLETION_EXCLUDE_PATTERN:-"/(build|integTest|out)/"}
 
-	if [[ ! $(find $cache_dir/$cache_name -mmin -$cache_ttl_mins 2> /dev/null) ]]; then
+	if [[ ! $(find "$cache_dir/$cache_name" -mmin "-$cache_ttl_mins" 2> /dev/null) ]]; then
 		# Cache all Gradle scripts
-		local gradle_build_scripts=$(find $project_root_dir -type f -name "*.gradle" -o -name "*.gradle.kts" 2> /dev/null | grep -E -v "$script_exclude_pattern")
-		printf "%s\n" "${gradle_build_scripts[@]}" > $cache_dir/$cache_name
+		local gradle_build_scripts
+		gradle_build_scripts=$(
+			find "$project_root_dir" -type f \
+				\( -name "*.gradle" -o -name "*.gradle.kts" \) 2> /dev/null \
+				| grep -E -v "$script_exclude_pattern"
+		)
+		printf "%s\n" "${gradle_build_scripts[@]}" > "$cache_dir/$cache_name"
 	fi
 }
 
@@ -115,7 +121,10 @@ __gradle-long-options() {
 --system-prop           - Set a system property
 --version               - Prints Gradle version info
 --warn                  - Log warnings and errors only"
-	COMPREPLY=($(compgen -W "$args" -- "${COMP_WORDS[COMP_CWORD]}"))
+	COMPREPLY=()
+	while IFS='' read -r line; do
+		COMPREPLY+=("$line")
+	done < <(compgen -W "$args" -- "${COMP_WORDS[COMP_CWORD]}")
 }
 
 __gradle-properties() {
@@ -130,7 +139,10 @@ __gradle-properties() {
 -Dorg.gradle.parallel=            - Set true to enable parallel project builds (incubating)
 -Dorg.gradle.parallel.intra=      - Set true to enable intra-project parallel builds (incubating)
 -Dorg.gradle.workers.max=         - Set the number of workers Gradle is allowed to use"
-	COMPREPLY=($(compgen -W "$args" -- "${COMP_WORDS[COMP_CWORD]}"))
+	COMPREPLY=()
+	while IFS='' read -r line; do
+		COMPREPLY+=("$line")
+	done < <(compgen -W "$args" -- "${COMP_WORDS[COMP_CWORD]}")
 	return 0
 }
 
@@ -156,7 +168,8 @@ __gradle-short-options() {
 -I                      - Specifies an initialization script
 -P                      - Sets a project property of the root project
 -S                      - Print out the full (very verbose) stacktrace"
-	COMPREPLY=($(compgen -W "$args" -- "${COMP_WORDS[COMP_CWORD]}"))
+	COMPREPLY=()
+	while IFS='' read -r line; do COMPREPLY+=("$line"); done < <(compgen -W "$args" -- "${COMP_WORDS[COMP_CWORD]}")
 }
 
 __gradle-notify-tasks-cache-build() {
@@ -179,10 +192,10 @@ __gradle-generate-tasks-cache() {
 	# Run gradle to retrieve possible tasks and cache.
 	# Reuse Gradle Daemon if IDLE but don't start a new one.
 	local gradle_tasks_output
-	if [[ ! -z "$($gradle_cmd --status 2> /dev/null | grep IDLE)" ]]; then
-		gradle_tasks_output="$($gradle_cmd -b $gradle_build_file --daemon -q tasks --all)"
+	if "$gradle_cmd" --status 2> /dev/null | grep -q IDLE; then
+		gradle_tasks_output="$("$gradle_cmd" -b "$gradle_build_file" --daemon -q tasks --all)"
 	else
-		gradle_tasks_output="$($gradle_cmd -b $gradle_build_file --no-daemon -q tasks --all)"
+		gradle_tasks_output="$("$gradle_cmd" -b "$gradle_build_file" --no-daemon -q tasks --all)"
 	fi
 	local output_line
 	local task_description
@@ -206,15 +219,18 @@ __gradle-generate-tasks-cache() {
 
 	# subproject tasks can be referenced implicitly from root project
 	if [[ $GRADLE_COMPLETION_UNQUALIFIED_TASKS == "true" ]]; then
-		local -a implicit_tasks=()
-		implicit_tasks=($(comm -23 <(printf "%s\n" "${subproject_tasks[@]}" | sort) <(printf "%s\n" "${root_tasks[@]}" | sort)))
-		for task in $(printf "%s\n" "${implicit_tasks[@]}"); do
-			gradle_all_tasks+=($task)
+		local -a implicit_tasks
+		while IFS='' read -r line; do
+			implicit_tasks+=("$line")
+		done < <(comm -23 <(printf "%s\n" "${subproject_tasks[@]}" | sort) \
+			<(printf "%s\n" "${root_tasks[@]}" | sort))
+		for task in "${implicit_tasks[@]}"; do
+			gradle_all_tasks+=("$task")
 		done
 	fi
 
-	printf "%s\n" "${gradle_all_tasks[@]}" > $cache_dir/$gradle_files_checksum
-	echo $gradle_files_checksum > $cache_dir/$cache_name.md5
+	printf "%s\n" "${gradle_all_tasks[@]}" > "$cache_dir/$gradle_files_checksum"
+	echo "$gradle_files_checksum" > "$cache_dir/$cache_name.md5"
 }
 
 __gradle-completion-init() {
@@ -262,22 +278,30 @@ _gradle() {
 			__gradle-set-files-checksum
 
 			# The cache key is md5 sum of all gradle scripts, so it's valid if it exists.
-			if [[ -f $cache_dir/$cache_name.md5 ]]; then
-				local cached_checksum="$(cat $cache_dir/$cache_name.md5)"
+			if [[ -f "$cache_dir/$cache_name.md5" ]]; then
+				local cached_checksum
+				cached_checksum="$(cat "$cache_dir/$cache_name.md5")"
 				local -a cached_tasks
 				if [[ -z $cur ]]; then
-					cached_tasks=($(cat $cache_dir/$cached_checksum))
+					while IFS='' read -r line; do
+						cached_tasks+=("$line")
+					done < "$cache_dir/$cached_checksum"
 				else
-					cached_tasks=($(grep "^$cur" $cache_dir/$cached_checksum))
+					while IFS='' read -r line; do
+						cached_tasks+=("$line")
+					done < <(grep "^$cur" "$cache_dir/$cached_checksum")
 				fi
-				COMPREPLY=($(compgen -W "${cached_tasks[*]}" -- "$cur"))
+				while IFS='' read -r line; do
+					COMPREPLY+=("$line")
+				done < <(compgen -W "${cached_tasks[*]}" -- "$cur")
 			else
 				__gradle-notify-tasks-cache-build
 			fi
 
 			# Regenerate tasks cache in the background
-			if [[ $gradle_files_checksum != "$(cat $cache_dir/$cache_name.md5)" || ! -f $cache_dir/$gradle_files_checksum ]]; then
-				$(__gradle-generate-tasks-cache 1>&2 2> /dev/null &)
+			if [[ $gradle_files_checksum != "$(cat "$cache_dir/$cache_name.md5")" ||
+			! -f "$cache_dir/$gradle_files_checksum" ]]; then
+				(__gradle-generate-tasks-cache &> /dev/null &)
 			fi
 		else
 			# Default tasks available outside Gradle projects
@@ -293,7 +317,10 @@ projects             - Displays the sub-projects of root project.
 properties           - Displays the properties of root project.
 tasks                - Displays the tasks runnable from root project.
 wrapper              - Generates Gradle wrapper files."
-			COMPREPLY=($(compgen -W "$args" -- "${COMP_WORDS[COMP_CWORD]}"))
+			COMPREPLY=()
+			while IFS='' read -r line; do
+				COMPREPLY+=("$line")
+			done < <(compgen -W "${args}" -- "${cur}")
 		fi
 	fi
 
@@ -301,7 +328,7 @@ wrapper              - Generates Gradle wrapper files."
 
 	# Remove description ("[:space:]" and after) if only one possibility
 	if [[ ${#COMPREPLY[*]} -eq 1 ]]; then
-		COMPREPLY=(${COMPREPLY[0]%%  *})
+		COMPREPLY=("${COMPREPLY[0]%%  *}")
 	fi
 
 	return 0
diff --git a/completion/available/homesick.completion.bash b/completion/available/homesick.completion.bash
index ed6f6e79ed..41ab67f146 100644
--- a/completion/available/homesick.completion.bash
+++ b/completion/available/homesick.completion.bash
@@ -1,2 +1,3 @@
+# shellcheck shell=bash
 _log_warning 'Bash completion for "homesick" is now deprecated, as it used unlicensed code.
 Please disable this completion and use the instructions from "homesick" bash completion developers instead.'
diff --git a/completion/available/maven.completion.bash b/completion/available/maven.completion.bash
index 54c28c4d2a..780fed3161 100644
--- a/completion/available/maven.completion.bash
+++ b/completion/available/maven.completion.bash
@@ -28,7 +28,7 @@ _mvn() {
 	COMPREPLY=($(compgen -W "$cmds" -- "$cur"))
 	local i=${#COMPREPLY[*]}
 	while [ "$((--i))" -ge 0 ]; do
-		COMPREPLY[$i]=${COMPREPLY[$i]#"$colonprefixes"}
+		COMPREPLY[i]=${COMPREPLY[i]#"$colonprefixes"}
 	done
 
 	return 0
diff --git a/completion/available/minishift.completion.bash b/completion/available/minishift.completion.bash
index 5679eae80f..c48f84b1bd 100644
--- a/completion/available/minishift.completion.bash
+++ b/completion/available/minishift.completion.bash
@@ -1 +1,3 @@
+# shellcheck shell=bash
+# shellcheck disable=SC1090
 _command_exists minishift && source <(minishift completion bash)
diff --git a/completion/available/openshift.completion.bash b/completion/available/openshift.completion.bash
index 1e7b681506..c0f525b868 100644
--- a/completion/available/openshift.completion.bash
+++ b/completion/available/openshift.completion.bash
@@ -1 +1,3 @@
+# shellcheck shell=bash
+# shellcheck disable=SC1090
 _command_exists oc && source <(oc completion bash)
diff --git a/completion/available/pew.completion.bash b/completion/available/pew.completion.bash
index 24b133f9db..3b203d4c16 100644
--- a/completion/available/pew.completion.bash
+++ b/completion/available/pew.completion.bash
@@ -1,4 +1,5 @@
 # shellcheck shell=bash
+# shellcheck disable=SC1090
 
 if _command_exists pew; then
 	source "$(pew shell_config)"
diff --git a/completion/available/rvm.completion.bash b/completion/available/rvm.completion.bash
index cd8ded0468..11530e4295 100644
--- a/completion/available/rvm.completion.bash
+++ b/completion/available/rvm.completion.bash
@@ -1,5 +1,6 @@
-#!/usr/bin/env bash
-# Bash completion support for  RVM.
+# shellcheck shell=bash
+# shellcheck disable=SC2154,SC1091
+# Bash completion support for RVM.
 # Source: https://rvm.io/workflow/completion
 
-[[ -r $rvm_path/scripts/completion ]] && . $rvm_path/scripts/completion
+[[ -r $rvm_path/scripts/completion ]] && . "$rvm_path/scripts/completion"
diff --git a/completion/available/todo.completion.bash b/completion/available/todo.completion.bash
index b5517d8654..7281a7e893 100644
--- a/completion/available/todo.completion.bash
+++ b/completion/available/todo.completion.bash
@@ -1,2 +1,3 @@
+# shellcheck shell=bash
 _log_warning 'Bash completion for "todo.txt-cli" is now deprecated, as it used code with incompatible license.
 Please disable this completion and use the instructions from "todo.txt-cli" developers instead.'
diff --git a/completion/available/travis.completion.bash b/completion/available/travis.completion.bash
index f533cde037..4df1fa2b3b 100644
--- a/completion/available/travis.completion.bash
+++ b/completion/available/travis.completion.bash
@@ -1,4 +1,5 @@
 # shellcheck shell=bash
+# shellcheck disable=SC1090
 
 if _command_exists travis; then
 	if [[ -s "${__TRAVIS_COMPLETION_SCRIPT:=${TRAVIS_CONFIG_PATH:-${HOME}/.travis}/travis.sh}" ]]; then
diff --git a/completion/available/vagrant.completion.bash b/completion/available/vagrant.completion.bash
index 31a4ae1369..aadc18ab7e 100644
--- a/completion/available/vagrant.completion.bash
+++ b/completion/available/vagrant.completion.bash
@@ -1,4 +1,4 @@
-#!/bin/bash
+# shellcheck shell=bash
 
 # (The MIT License)
 #
@@ -26,21 +26,21 @@ __pwdln() {
 	pwdmod="${PWD}/"
 	itr=0
 	until [[ -z "$pwdmod" ]]; do
-		itr=$(($itr + 1))
+		itr=$((itr + 1))
 		pwdmod="${pwdmod#*/}"
 	done
-	echo -n $(($itr - 1))
+	echo -n $((itr - 1))
 }
 
 __vagrantinvestigate() {
-	if [ -f "${PWD}/.vagrant" -o -d "${PWD}/.vagrant" ]; then
+	if [ -f "${PWD}/.vagrant" ] || [ -d "${PWD}/.vagrant" ]; then
 		echo "${PWD}/.vagrant"
 		return 0
 	else
 		pwdmod2="${PWD}"
 		for ((i = 2; i <= $(__pwdln); i++)); do
 			pwdmod2="${pwdmod2%/*}"
-			if [ -f "${pwdmod2}/.vagrant" -o -d "${pwdmod2}/.vagrant" ]; then
+			if [ -f "${pwdmod2}/.vagrant" ] || [ -d "${pwdmod2}/.vagrant" ]; then
 				echo "${pwdmod2}/.vagrant"
 				return 0
 			fi
@@ -54,74 +54,86 @@ _vagrant() {
 	prev="${COMP_WORDS[COMP_CWORD - 1]}"
 	commands="box cloud destroy global-status halt help hostmanager init login package plugin port powershell provision push rdp reload resume scp snapshot ssh ssh-config status suspend up upload validate vbguest version winrm winrm-config"
 
-	if [ $COMP_CWORD == 1 ]; then
-		COMPREPLY=($(compgen -W "${commands}" -- ${cur}))
+	if ((COMP_CWORD == 1)); then
+		COMPREPLY=()
+		while IFS='' read -r line; do COMPREPLY+=("$line"); done < <(compgen -W "${commands}" -- "${cur}")
 		return 0
 	fi
 
-	if [ $COMP_CWORD == 2 ]; then
+	if ((COMP_CWORD == 2)); then
 		case "$prev" in
 			"init")
-				local box_list=$(find "$HOME/.vagrant.d/boxes" -mindepth 1 -maxdepth 1 -type d -exec basename {} \; | sed -e 's/-VAGRANTSLASH-/\//')
-				COMPREPLY=($(compgen -W "${box_list}" -- ${cur}))
+				local box_list
+				box_list=$(find "$HOME/.vagrant.d/boxes" -mindepth 1 -maxdepth 1 -type d -exec basename {} \; | sed -e 's/-VAGRANTSLASH-/\//')
+				COMPREPLY=()
+				while IFS='' read -r line; do COMPREPLY+=("$line"); done < <(compgen -W "${box_list}" -- "${cur}")
 				return 0
 				;;
 			"up")
 				vagrant_state_file=$(__vagrantinvestigate) || return 1
 				if [[ -d $vagrant_state_file ]]; then
-					vm_list=$(find $vagrant_state_file/machines -mindepth 1 -maxdepth 1 -type d -exec basename {} \;)
+					vm_list=$(find "$vagrant_state_file/machines" -mindepth 1 -maxdepth 1 -type d -exec basename {} \;)
 				fi
 				local up_commands="--no-provision"
-				COMPREPLY=($(compgen -W "${up_commands} ${vm_list}" -- ${cur}))
+				COMPREPLY=()
+				while IFS='' read -r line; do COMPREPLY+=("$line"); done < <(compgen -W "${up_commands} ${vm_list}" -- "${cur}")
 				return 0
 				;;
 			"ssh" | "provision" | "reload" | "halt" | "suspend" | "resume" | "ssh-config")
 				vagrant_state_file=$(__vagrantinvestigate) || return 1
 				if [[ -f $vagrant_state_file ]]; then
-					running_vm_list=$(grep 'active' $vagrant_state_file | sed -e 's/"active"://' | tr ',' '\n' | cut -d '"' -f 2 | tr '\n' ' ')
+					running_vm_list=$(grep 'active' "$vagrant_state_file" | sed -e 's/"active"://' | tr ',' '\n' | cut -d '"' -f 2 | tr '\n' ' ')
 				else
-					running_vm_list=$(find $vagrant_state_file -type f -name "id" | awk -F"/" '{print $(NF-2)}')
+					running_vm_list=$(find "$vagrant_state_file" -type f -name "id" | awk -F"/" '{print $(NF-2)}')
 				fi
-				COMPREPLY=($(compgen -W "${running_vm_list}" -- ${cur}))
+				COMPREPLY=()
+				while IFS='' read -r line; do COMPREPLY+=("$line"); done < <(compgen -W "${running_vm_list}" -- "${cur}")
 				return 0
 				;;
 			"box")
 				box_commands="add list outdated prune remove repackage update"
-				COMPREPLY=($(compgen -W "${box_commands}" -- ${cur}))
+				COMPREPLY=()
+				while IFS='' read -r line; do COMPREPLY+=("$line"); done < <(compgen -W "${box_commands}" -- "${cur}")
 				return 0
 				;;
 			"plugin")
 				plugin_commands="expunge install license list repair uninstall update"
-				COMPREPLY=($(compgen -W "${plugin_commands}" -- ${cur}))
+				COMPREPLY=()
+				while IFS='' read -r line; do COMPREPLY+=("$line"); done < <(compgen -W "${plugin_commands}" -- "${cur}")
 				return 0
 				;;
 			"help")
-				COMPREPLY=($(compgen -W "${commands}" -- ${cur}))
+				COMPREPLY=()
+				while IFS='' read -r line; do COMPREPLY+=("$line"); done < <(compgen -W "${commands}" -- "${cur}")
 				return 0
 				;;
 			"snapshot")
 				snapshot_commands="delete list pop push restore save"
-				COMPREPLY=($(compgen -W "${snapshot_commands}" -- ${cur}))
+				COMPREPLY=()
+				while IFS='' read -r line; do COMPREPLY+=("$line"); done < <(compgen -W "${snapshot_commands}" -- "${cur}")
 				return 0
 				;;
 			*) ;;
 		esac
 	fi
 
-	if [ $COMP_CWORD == 3 ]; then
+	if ((COMP_CWORD == 3)); then
 		action="${COMP_WORDS[COMP_CWORD - 2]}"
 		case "$action" in
 			"up")
 				if [ "$prev" == "--no-provision" ]; then
-					COMPREPLY=($(compgen -W "${vm_list}" -- ${cur}))
+					COMPREPLY=()
+					while IFS='' read -r line; do COMPREPLY+=("$line"); done < <(compgen -W "${vm_list}" -- "${cur}")
 					return 0
 				fi
 				;;
 			"box")
 				case "$prev" in
 					"remove" | "repackage")
-						local box_list=$(find "$HOME/.vagrant.d/boxes" -mindepth 1 -maxdepth 1 -type d -exec basename {} \; | sed -e 's/-VAGRANTSLASH-/\//')
-						COMPREPLY=($(compgen -W "${box_list}" -- ${cur}))
+						local box_list
+						box_list=$(find "$HOME/.vagrant.d/boxes" -mindepth 1 -maxdepth 1 -type d -exec basename {} \; | sed -e 's/-VAGRANTSLASH-/\//')
+						COMPREPLY=()
+						while IFS='' read -r line; do COMPREPLY+=("$line"); done < <(compgen -W "${box_list}" -- "${cur}")
 						return 0
 						;;
 					*) ;;
@@ -129,21 +141,24 @@ _vagrant() {
 				;;
 			"snapshot")
 				if [ "$prev" == "restore" ]; then
-					COMPREPLY=($(compgen -W "${vm_list}" -- ${cur}))
+					COMPREPLY=()
+					while IFS='' read -r line; do COMPREPLY+=("$line"); done < <(compgen -W "${vm_list}" -- "${cur}")
 					return 0
 				fi
 				;;
 		esac
 	fi
 
-	if [ $COMP_CWORD == 4 ]; then
+	if ((COMP_CWORD == 4)); then
 		action="${COMP_WORDS[COMP_CWORD - 3]}"
 		prev="${COMP_WORDS[COMP_CWORD - 2]}"
 		case "$action" in
 			"snapshot")
 				if [ "$prev" == "restore" ]; then
-					local snapshot_list="$(vagrant snapshot list ${cur} 2> /dev/null | awk '{ORS=" "} /==>/ {next} {print}')"
-					COMPREPLY=($(compgen -W "${snapshot_list}" -- ${cur}))
+					local snapshot_list
+					snapshot_list="$(vagrant snapshot list "${cur}" 2> /dev/null | awk '{ORS=" "} /==>/ {next} {print}')"
+					COMPREPLY=()
+					while IFS='' read -r line; do COMPREPLY+=("$line"); done < <(compgen -W "${snapshot_list}" -- "${cur}")
 					return 0
 				fi
 				;;
diff --git a/completion/available/virsh.completion.bash b/completion/available/virsh.completion.bash
index 6450b4a305..beab7f0b3c 100644
--- a/completion/available/virsh.completion.bash
+++ b/completion/available/virsh.completion.bash
@@ -1,2 +1,3 @@
+# shellcheck shell=bash
 _log_warning 'Bash completion for "virsh" is now deprecated, as it used code with incompatible license.
 Please disable this completion and use the instructions from "virsh" developers instead.'