[wifi] capture-sample: shellcheck & checkbashisms

wifi/capture-sample.sh

@@ -52,7 +52,7 @@ CHANNEL=1
 # Displays the message in argument on the error output and exits
 error()
 {
-	echo "$1" >&2
+	printf '%s\n' "$1" >&2
 	clean
 	exit 1
 }
@@ -66,7 +66,7 @@ clean()
 # Verifies the presence of the needed programs
 check_dependencies()
 {
-	which tcpdump >/dev/null \
+	command -v tcpdump >/dev/null \
 		|| error "tcpdump is required to run this program!"
 
 	if [ "$OS" = Linux ] ; then
@@ -80,25 +80,25 @@ check_dependencies()
 iface_set_channel()
 {
 	echo "Setting interface $IFACE on channel $1..."
-	case $OS in
+	case "$OS" in
 		Linux)
 			iface_down
-			iwconfig $IFACE mode managed
+			iwconfig "$IFACE" mode managed
 			iface_up
-			iwconfig $IFACE channel $1
+			iwconfig "$IFACE" channel "$1"
 			;;
 		NetBSD | OpenBSD)
 			iface_down
-			ifconfig $IFACE media autoselect chan $1
+			ifconfig "$IFACE" media autoselect chan "$1"
 			iface_up
 			;;
 		*)
 			error "Your OS is not supported."
 			;;
 	esac \
-		&& echo "Channel set." \
 		|| error "Cannot set the channel!"
 
+	echo "Channel set."
 	iface_monitor
 }
 
@@ -107,54 +107,56 @@ iface_monitor()
 {
 	iface_down
 
-	echo -n "Switching interface $IFACE to monitor mode... "
-	case $OS in
+	printf 'Switching interface %s to monitor mode... ' "$IFACE"
+	case "$OS" in
 		Linux)
-			iwconfig $IFACE mode monitor
+			iwconfig "$IFACE" mode monitor
 			;;
 		NetBSD | OpenBSD)
-			ifconfig $IFACE media autoselect mediaopt monitor
+			ifconfig "$IFACE" media autoselect mediaopt monitor
 			;;
 		*)
 			error "Your OS is not supported."
 			;;
 	esac \
-		&& echo "OK." \
 		|| error "Cannot switch the interface to monitor mode!"
 
+	echo "OK."
 	iface_up
 }
 
 # Shuts down the capture interface
 iface_down()
 {
-	echo -n "Shuting down interface $IFACE... "
-	ifconfig $IFACE down && echo "OK." \
+	printf 'Shuting down interface %s... ' "$IFACE"
+	ifconfig "$IFACE" down \
 		|| error "Cannot shut down the interface!"
+	echo "OK."
 }
 
 # Turns on the capture interface
 iface_up()
 {
-	echo -n "Turning up interface $IFACE... "
-	ifconfig $IFACE up && echo "OK." \
+	printf 'Turning up interface %s... ' "$IFACE"
+	ifconfig "$IFACE" up \
 		|| error "Cannot turn the interface up!"
+	echo "OK."
 }
 
 # Invokes tcpdump and displays the number of packets captured
 invoke_tcpdump()
 {
-	NCAP=$(tcpdump -i $IFACE -c $NB_PKT -w "$FILE" 2>&1 \
+	NCAP=$(tcpdump -i "$IFACE" -c "$NB_PKT" -w "$FILE" 2>&1 \
 		| sed -nr 's/([[:digit:]]+) packets received by filter$/\1/p')
-	[ "$NCAP" = "" ] \
+	[ -z "$NCAP" ] \
 		&& error "Error parsing the tcpdump messages! (NCAP=\"$NCAP\")"
-	echo $NCAP
+	echo "$NCAP"
 }
 
 # Waits for a number of seconds, then kills any tcpdump process
 wait_tcpdump()
 {
-	sleep $1
+	sleep "$1"
 	echo "$1 seconds passed, killing all tcpdump processes..."
 	pkill tcpdump
 }
@@ -162,15 +164,15 @@ wait_tcpdump()
 # Gets some information about the running system
 gather_system_information()
 {
-	echo -n "Gathering system information... "
+	printf "Gathering system information... "
 	# Kernel & other information:
 	uname -a >"$DESTDIR"/uname-a
 	# Wi-Fi interface information:
-	ifconfig $IFACE >"$DESTDIR"/ifconfig_$IFACE
-	[ $OS = Linux ] \
-		&& iwconfig $IFACE >"$DESTDIR"/iwconfig_$IFACE
+	ifconfig "$IFACE" >"$DESTDIR/ifconfig_$IFACE"
+	[ "$OS" = Linux ] \
+		&& iwconfig "$IFACE" >"$DESTDIR/iwconfig_$IFACE"
 	# PCI devices:
-	which lspci >/dev/null \
+	command -v lspci >/dev/null \
 		&& lspci >"$DESTDIR"/lspci \
 		|| echo "lspci not available! Please install pciutils. "
 	# USB devices:
@@ -183,14 +185,14 @@ gather_system_information()
 # Gets information about the plugged usb devices
 gather_usb_devices()
 {
-	case $OS in
+	case "$OS" in
 		Linux)
-			which lsusb >/dev/null \
+			command -v lsusb >/dev/null \
 				&& lsusb >"$DESTDIR"/lsusb \
 				|| echo "lsusb not available! Please install usbutils. "
 			;;
 		NetBSD | OpenBSD | DragonFly)
-			which usbstats >/dev/null \
+			command -v usbstats >/dev/null \
 				&& usbstats >"$DESTDIR"/usbstats \
 				|| echo "usbstats not available! Please install usbutil. "
 			;;
@@ -200,7 +202,7 @@ gather_usb_devices()
 # Gets information about the loaded kernel modules
 gather_kernel_modules()
 {
-	case $OS in
+	case "$OS" in
 		Linux)
 			lsmod >"$DESTDIR"/lsmod
 			;;
@@ -217,7 +219,7 @@ gather_kernel_modules()
 create_archive()
 {
 	TARBALL="${DESTDIR}.tar.gz"
-	DIR=`basename "$DESTDIR"`
+	DIR=$(basename "$DESTDIR")
 	tar -C "$TMP" -czf "$TARBALL" "$DIR"
 	echo "Archive \"$TARBALL\" created."
 }
@@ -231,14 +233,14 @@ create_archive()
 # Interface to capture from:
 IFACE=$1
 # Machine information:
-OS=`uname`
-OS_RELEASE=`uname -r`
-HOSTNAME=`uname -n`
+OS=$(uname)
+OS_RELEASE=$(uname -r)
+HOSTNAME=$(uname -n)
 # Current date:
-DATE=`date +%FT%H%M%S`
+DATE=$(date +%FT%H%M%S)
 # Temporary destination directory:
 DESTDIR=$(mktemp -d \
-	"$TMP"/capture_${OS}-${OS_RELEASE}_${IFACE}_${HOSTNAME}_${DATE}_XXX)
+	"$TMP/capture_${OS}-${OS_RELEASE}_${IFACE}_${HOSTNAME}_${DATE}_XXX")
 # Update capture file with full path:
 FILE="$DESTDIR/$FILE"
 
@@ -246,26 +248,25 @@ check_dependencies
 
 echo "Trying to capture $NB_PKT packets..."
 CAPTURED=0
-while [ $CAPTURED -eq 0 -a $CHANNEL -le 14 ] ; do
+while [ "$CAPTURED" -eq 0 ] && [ "$CHANNEL" -le 14 ] ; do
 	echo
-	iface_set_channel $CHANNEL
-	wait_tcpdump $TIMEOUT &
+	iface_set_channel "$CHANNEL"
+	wait_tcpdump "$TIMEOUT" &
 	CAPTURED=$(invoke_tcpdump)
-	[ $CAPTURED -eq 0 ] \
+	[ "$CAPTURED" -eq 0 ] \
 		&& echo "No packet captured on channel $CHANNEL." \
 		|| echo "$CAPTURED packets captured on channel $CHANNEL."
-	CHANNEL=`expr $CHANNEL + 1`
+	CHANNEL=$((CHANNEL + 1))
 done
 
 echo
-[ $CAPTURED -gt 0 ] \
-	&& echo "Capture file \"$FILE\" created." \
+[ "$CAPTURED" -gt 0 ] \
 	|| error "Failed to capture any packet!"
+echo "Capture file \"$FILE\" created."
 
 gather_system_information
 create_archive
 clean
 
-echo
-echo "You can now shut down the interface $IFACE if you want:"
-echo "	ifconfig $IFACE down"
+printf '\nYou can now shut down the interface %s if you would like:\n' "$IFACE"
+printf '\tifconfig %s down\n' "$IFACE"