Prefer [[ ]] to [ ].

See http://mywiki.wooledge.org/BashFAQ/031 - generally, [[ ]] is less error-prone.

Author: lorenzo-stoakes

kerndev-build

@@ -7,10 +7,10 @@ set -e; set -o pipefail; source kerndev-shared.sh
 target_arch=${1:-"x86_64"}
 
 # Sanity checks.
-[ ! -d $LINUX_DEV_PATH ] && fatal "can't find linux dev path at $LINUX_DEV_PATH"
-[ ! -f $LINUX_DEV_PATH/REPORTING-BUGS ] && \
+[[ ! -d $LINUX_DEV_PATH ]] && fatal "can't find linux dev path at $LINUX_DEV_PATH"
+[[ ! -f $LINUX_DEV_PATH/REPORTING-BUGS ]] && \
 	fatal "Doesn't look like a linux dev path: $LINUX_DEV_PATH"
-[ $EUID = 0 ] && fatal "Don't run as root, causes file ownership pain"
+[[ $EUID = 0 ]] && fatal "Don't run as root, causes file ownership pain"
 
 case $target_arch in
 arm)
@@ -27,7 +27,7 @@ aarch64)
 	;;
 esac
 
-if [ "$target_arch" != "x86_64" ]; then
+if [[ "$target_arch" != "x86_64" ]]; then
 	# Make sure we have cross-compilers. `gcc` check should suffice.
 	check_exists ${cross_compile_prefix}gcc
 
@@ -51,7 +51,7 @@ echo Compiling kernel...
 # 1 extra thread to account for I/O waiting.
 mak -j$((cores + 1))
 
-if [ -z "$DONT_INSTALL" ]; then
+if [[ -z "$DONT_INSTALL" ]]; then
 	NO_DONE=y sudo -E kerndev-install $target_arch
 fi
 

kerndev-check-all

@@ -9,7 +9,7 @@ check_opts="-f -q --show-types --no-summary"
 
 # Ensure the files exist, if not, die.
 for file in $args; do
-	(! is_opt $file) && [ ! -f $file ] && \
+	(! is_opt $file) && [[ ! -f $file ]] && \
 		fatal "Can't find $file."
 done
 

kerndev-config

@@ -3,7 +3,7 @@ set -e; set -o pipefail; source kerndev-shared.sh
 
 push_linux
 
-if [ -n "$REBUILD" ] || [ ! -f .config ]; then
+if [[ -n "$REBUILD" ]] || [[ ! -f .config ]]; then
 	mak mrproper
 	mak defconfig
 fi
@@ -39,7 +39,7 @@ kenable ikconfig ikconfig_proc
 scripts/config --set-str uevent_helper_path ""
 
 # Optionally enable flags for docker support.
-[ -n "$ENABLE_DOCKER_SUPPORT" ] && \
+[[ -n "$ENABLE_DOCKER_SUPPORT" ]] && \
     kenable netfilter_advanced dm_thin_provisioning bridge bridge_netfilter \
 	    devpts_multiple_instances cgroup_device memcg macvlan veth \
 	    nf_nat_ipv4 nf_nat netfilter_xt_match_{conntrack,addrtype} \
@@ -48,7 +48,7 @@ scripts/config --set-str uevent_helper_path ""
 	    cgroup_net_prio btrfs_fs
 
 # Optionally, we are interested in code coverage.
-[ -n "$ENABLE_GCOV" ] && \
+[[ -n "$ENABLE_GCOV" ]] && \
 	kenable debug_fs gcov_kernel gcov_format_autodetect gcov_profile_all
 
 pop

kerndev-create

@@ -21,13 +21,13 @@ case $target_arch in
 esac
 
 # Sanity checks.
-[ ! -f "/etc/arch-release" ] && \
+[[ ! -f "/etc/arch-release" ]] && \
 	fatal This script is designed for arch linux only, sorry!
 
 check_exists kerndev-create.chroot.sh kerndev-build kerndev-install pacstrap \
 	    truncate mkfs.ext4 arch-chroot
 
-[ -n $USE_EXISTING_IMAGE ] && [ ! -f $KERNDEV_PATH/rootfs.img ] && \
+[[ -n $USE_EXISTING_IMAGE ]] && [[ ! -f $KERNDEV_PATH/rootfs.img ]] && \
 	fatal "can't find existing rootfs image"
 
 chroot_script_path=$(which kerndev-create.chroot.sh)
@@ -36,7 +36,7 @@ chroot_script_path=$(which kerndev-create.chroot.sh)
 elevate $@
 
 # We want access to the underlying user.
-[ -z "$SUDO_USER" ] && fatal please run this using sudo!
+[[ -z "$SUDO_USER" ]] && fatal please run this using sudo!
 
 # If this fails due to being unable to unmount /mnt, mount below will fail so we
 # can get away with ||true here.
@@ -46,7 +46,7 @@ mkdir -p $KERNDEV_PATH
 
 push_kerndev
 
-if [ -z "$USE_EXISTING_IMAGE" ]; then
+if [[ -z "$USE_EXISTING_IMAGE" ]]; then
 	echo Creating and formatting rootfs image file...
 	rm -f rootfs.img
 	truncate -s $IMAGE_SIZE rootfs.img
@@ -58,7 +58,7 @@ fi
 mount_image rootfs.img
 trap "umount /mnt" EXIT
 
-if [ -z "$USE_EXISTING_IMAGE" ]; then
+if [[ -z "$USE_EXISTING_IMAGE" ]]; then
 	echo Downloading and installing rootfs into image...
 	pacstrap /mnt base base-devel &>/dev/null
 fi
@@ -78,7 +78,7 @@ EOF
 
 echo ...chroot-ed script complete!
 
-if [ -z "$USE_EXISTING_IMAGE" ] && [ -n "$ENABLE_GCOV" ]; then
+if [[ -z "$USE_EXISTING_IMAGE" ]] && [[ -n "$ENABLE_GCOV" ]]; then
     echo Generating gcov script...
 
 	# Create 'cov' tool to check coverage for a specific file in the kernel tree.
@@ -87,7 +87,7 @@ if [ -z "$USE_EXISTING_IMAGE" ] && [ -n "$ENABLE_GCOV" ]; then
 	cat >$cov_path <<-EOF
 		#!/bin/bash
 
-		[ -z "\$1" ] && echo "usage: \$(basename \$0) [relative path to source file]" >&2 && exit 1
+		[[ -z "\$1" ]] && echo "usage: \$(basename \$0) [relative path to source file]" >&2 && exit 1
 
 		# ref: https://goo.gl/rnd6yo
 		args=\${@:1:-1}
@@ -106,7 +106,7 @@ if [ -z "$USE_EXISTING_IMAGE" ] && [ -n "$ENABLE_GCOV" ]; then
 	pop
 fi
 
-if [ -n "$ACCESS_CHROOT" ]; then
+if [[ -n "$ACCESS_CHROOT" ]]; then
 	echo Entering chroot shell...
 	arch-chroot /mnt
 	echo ...chroot shell done!

kerndev-create-foreign

@@ -3,7 +3,7 @@ set -e; set -o pipefail; source kerndev-shared.sh
 
 # TODO: Duplicates kerndev-create, lots of copy-pasta, de-duplicate!!
 
-[ -z "$1" ] && fatal missing arch.
+[[ -z "$1" ]] && fatal missing arch.
 
 target_arch=$1
 shift
@@ -34,16 +34,16 @@ chroot_path="/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin"
 
 function cleanup()
 {
-	[ -f $binfmt_path/$target_arch ] && echo -1 > $binfmt_path/$target_arch
+	[[ -f $binfmt_path/$target_arch ]] && echo -1 > $binfmt_path/$target_arch
 	rm -f /mnt/usr/bin/qemu-$target_arch-static
 	unmount
 }
 
 # Sanity checks.
 check_exists debootstrap qemu-system-$target_arch qemu-$target_arch-static
-[ ! -d $binfmt_path ] && fatal "binfmt not available."
+[[ ! -d $binfmt_path ]] && fatal "binfmt not available."
 
-[ -n $USE_EXISTING_IMAGE ] && [ ! -f $KERNDEV_PATH/$rootfs ] && \
+[[ -n $USE_EXISTING_IMAGE ]] && [[ ! -f $KERNDEV_PATH/$rootfs ]] && \
 	fatal "can't find existing rootfs image"
 
 # So many commands need sudo, so just force the issue.
@@ -57,7 +57,7 @@ mkdir -p $KERNDEV_PATH
 
 push_kerndev
 
-if [ -z "$USE_EXISTING_IMAGE" ]; then
+if [[ -z "$USE_EXISTING_IMAGE" ]]; then
 	echo Creating and formatting rootfs image file...
 	rm -f $rootfs
 	truncate -s $IMAGE_SIZE $rootfs
@@ -67,7 +67,7 @@ fi
 mount_image $rootfs
 trap cleanup EXIT
 
-if [ -z "$USE_EXISTING_IMAGE" ]; then
+if [[ -z "$USE_EXISTING_IMAGE" ]]; then
 	echo "Downloading and installing first stage rootfs into image..."
 
 	debootstrap --arch=$debootstrap_arch --variant=minbase --foreign  \
@@ -79,7 +79,7 @@ echo Enabling binfmt for chroot...
 cp $(which qemu-${target_arch}-static) /mnt/usr/bin/
 echo "$binfmt_sig" > $binfmt_path/register
 
-if [ -z "$USE_EXISTING_IMAGE" ]; then
+if [[ -z "$USE_EXISTING_IMAGE" ]]; then
 	echo Entering chroot, downloading and installing second stage rootfs into image...
 	chroot /mnt /debootstrap/debootstrap --second-stage >/dev/null
 fi
@@ -103,7 +103,7 @@ nameserver 8.8.8.8
 nameserver 8.8.4.4
 EOF
 
-if [ -n "$ACCESS_CHROOT" ]; then
+if [[ -n "$ACCESS_CHROOT" ]]; then
 	echo Entering chroot shell...
 	arch-chroot /mnt env -i TERM=ansi PATH=$chroot_path /bin/bash
 	echo ...chroot shell done!

kerndev-create-foreign.chroot.sh

@@ -23,7 +23,7 @@ chroot_path="/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin"
 # Taken from http://unix.stackexchange.com/a/14346. Non-root version didn't work.
 function inside_chroot()
 {
-	[ "$(stat -c %d:%i /)" != "$(stat -c %d:%i /proc/1/root/.)" ]
+	[[ "$(stat -c %d:%i /)" != "$(stat -c %d:%i /proc/1/root/.)" ]]
 }
 
 function usage()
@@ -42,7 +42,7 @@ if ! inside_chroot; then
 	echo not inside chroot! >&2
 	exit 1
 fi
-if [ -z "$username" ]; then
+if [[ -z "$username" ]]; then
 	usage
 	exit 1
 fi
@@ -73,7 +73,7 @@ cat /etc/_hosts >> /etc/hosts
 rm /etc/_hosts
 
 echo Setting up root password...
-if [ -z "$password" ]; then
+if [[ -z "$password" ]]; then
 	# Don't let a typo ruin our day!
 	while ! passwd; do
 		echo Try again!

kerndev-create.chroot.sh

@@ -15,7 +15,7 @@ password=$2 # Optional, if not provided script will prompt.
 # Taken from http://unix.stackexchange.com/a/14346. Non-root version didn't work.
 function inside_chroot()
 {
-	[ "$(stat -c %d:%i /)" != "$(stat -c %d:%i /proc/1/root/.)" ]
+	[[ "$(stat -c %d:%i /)" != "$(stat -c %d:%i /proc/1/root/.)" ]]
 }
 
 function usage()
@@ -28,7 +28,7 @@ if ! inside_chroot; then
 	echo not inside chroot! >&2
 	exit 1
 fi
-if [ -z "$username" ]; then
+if [[ -z "$username" ]]; then
 	usage
 	exit 1
 fi
@@ -60,7 +60,7 @@ pacman -Sy --noconfirm btrfs-progs yaourt screen strace zsh lsof emacs-nox opens
 pacman -R --noconfirm linux &>/dev/null || true
 
 echo Setting up root password...
-if [ -z "$password" ]; then
+if [[ -z "$password" ]]; then
 	# Don't let a typo ruin our day!
 	while ! passwd; do
 	echo Try again!

kerndev-functions.sh

@@ -48,7 +48,7 @@ function push_kerndev()
 # If parameters are to be preserved, needs to be passed $@.
 function elevate()
 {
-	if [ $EUID != 0 ]; then
+	if [[ $EUID != 0 ]]; then
 		exec sudo -E $0 $@
 		exit $?
 	fi
@@ -85,7 +85,7 @@ function unmount()
 # $1: Directory to 'give back' to user $SUDO_USER.
 function give_back()
 {
-	[ -z "$SUDO_USER" ] && error "give_back: SUDO_USER not defined." || \
+	[[ -z "$SUDO_USER" ]] && error "give_back: SUDO_USER not defined." || \
 		chown -R $SUDO_USER:$SUDO_USER $1
 }
 
@@ -94,7 +94,7 @@ function give_back()
 # $@: make arguments.
 function mak()
 {
-	[ -z $VERBOSE ] && out="null" || out="tty"
+	[[ -z $VERBOSE ]] && out="null" || out="tty"
 
 	make $make_opts $@ >/dev/$out
 }
@@ -103,13 +103,13 @@ function mak()
 # $1: Argument.
 function is_opt()
 {
-	[[ $1 == -* ]]
+	[[[[ $1 == -* ]]]]
 }
 
 # Say we're done, if we're not configured to not do so.
 function say_done()
 {
-	[ -z "$NO_DONE" ] && echo Done! || true
+	[[ -z "$NO_DONE" ]] && echo Done! || true
 }
 
 

kerndev-install

@@ -16,25 +16,25 @@ x86_64)
 	rootfs=rootfs.img
 	kernel_image_path=$LINUX_DEV_PATH/arch/x86/boot/bzImage
 
-	[ ! -f $LINUX_DEV_PATH/REPORTING-BUGS ] && \
+	[[ ! -f $LINUX_DEV_PATH/REPORTING-BUGS ]] && \
 		fatal "doesn't look like a linux dev path: $LINUX_DEV_PATH"
-	[ ! -f $kernel_image_path ] && \
+	[[ ! -f $kernel_image_path ]] && \
 		fatal "can't find kernel image at $kernel_image_path"
 	;;
 *)
 	fatal "unknown architecture: $target_arch"
 	;;
 esac
 
-if [ "$target_arch" != "x86_64" ]; then
+if [[ "$target_arch" != "x86_64" ]]; then
 	rootfs=rootfs_${target_arch}.img
 	make_opts="ARCH=${linux_arch} CROSS_COMPILE=$cross_compile_prefix"
 fi
 
 # Sanity checks.
 
 rootfs_image_path=$KERNDEV_PATH/$rootfs
-[ ! -f $rootfs_image_path ] && \
+[[ ! -f $rootfs_image_path ]] && \
 	fatal "can't find root fs image at $rootfs_image_path"
 
 elevate $@
@@ -49,7 +49,7 @@ echo Installing headers and modules...
 mak headers_install INSTALL_HDR_PATH=/mnt/usr/
 mak modules_install INSTALL_MOD_PATH=/mnt/
 
-if [ -z "$USE_EXISTING_IMAGE" ] && [ -n "$ENABLE_GCOV" ]; then
+if [[ -z "$USE_EXISTING_IMAGE" ]] && [[ -n "$ENABLE_GCOV" ]]; then
 	# We need to copy the linux source code to be able to gcov it.
 	echo "Copying linux source to image (gcov)..."
 

kerndev-module-headers

@@ -16,14 +16,14 @@ function get_full_path()
 	echo "$( cd "$1" ; pwd -P )"
 }
 
-([ -z "$1" ] || ([ -f "$1" ] && [ ! -d "$1" ])) && usage
+([[ -z "$1" ]] || ([[ -f "$1" ]] && [[ ! -d "$1" ]])) && usage
 
 # Generate if doesn't exist.
 install -dm755 $1
 
 target_dir=$(get_full_path $1)
 karch=${2:-x86}
-if [ "$#" -gt 2 ]; then
+if [[ "$#" -gt 2 ]]; then
     shift 2
     make_opts="$@"
 fi
@@ -37,9 +37,9 @@ drivers/media/dvb-frontends drivers/media/usb/dvb-usb drivers/media/tuners"
 push_linux
 trap pop EXIT
 
-[ ! -f .config ] && fatal "Missing kernel configuration."
-[ ! -f Module.symvers ] && fatal "Missing Module.symvers, build kernel to generate."
-[ ! -d "$karch_dir" ] && fatal "Unrecognised karch: $karch"
+[[ ! -f .config ]] && fatal "Missing kernel configuration."
+[[ ! -f Module.symvers ]] && fatal "Missing Module.symvers, build kernel to generate."
+[[ ! -d "$karch_dir" ]] && fatal "Unrecognised karch: $karch"
 
 echo Running modules_prepare...
 make $make_opts modules_prepare >/dev/null
@@ -57,7 +57,7 @@ find include -mindepth 1 -maxdepth 1 -type d | \
     xargs -I {} cp -a "{}" "$target_dir/include"
 
 for d in include $extra_header_dirs; do
-	[ -d "$d" ] && mkdir -p "$target_dir/$d"
+	[[ -d "$d" ]] && mkdir -p "$target_dir/$d"
 done
 
 mkdir -p "$target_karch_dir"
@@ -76,12 +76,12 @@ cp "$karch_dir/Makefile" "$target_karch_dir"
 # May as well always copy these if available.
 for f in Makefile_32.cpu kernel/asm-offsets.s; do
 	p="$karch_dir/$f"
-	[ -f $p ] && cp "$p" "$target_karch_dir/$f"
+	[[ -f $p ]] && cp "$p" "$target_karch_dir/$f"
 done
 
 # Copy in extra headers. Directories already created above.
 for d in $extra_header_dirs; do
-	[ -d "$d" ] && cp $d/*.h "$target_dir/$d"
+	[[ -d "$d" ]] && cp $d/*.h "$target_dir/$d"
 done
 
 # Specific required files.