Minor code optimizations, add comments

Use a function that acts like `[ a = b ]` using case instead of
calling case every time, which results in a lot of repeated lines

fet.sh

@@ -1,36 +1,44 @@
 #!/bin/sh
 #
-#  this is my attempt at trying to make a fetch using only posix shell
-#   without any external commands
+#   fet.sh
+# a fetch in pure POSIX shell
 #
 
 # supress errors
 exec 2>/dev/null
 set --
+_() {  # [ a = b ] with globbing
+	! case $1 in  # default return is 0 so double negative saves a line
+		$2) return 1
+	esac
+}
 
 ## Terminal
 while [ ! "$term" ]; do
-	while IFS=':	' read -r key val; do
-		case $key in
-			PPid) ppid=$val; break;;
-		esac
+	# loop over lines in /proc/pid/status until it reaches PPid
+	# then save that to a variable and exit the file
+	while read -r line; do
+		_ "$line" "PPid*" && ppid=${line##*:?} && break
 	done < "/proc/${ppid:-$PPID}/status"
 
+	# get name of binary
 	read -r name < "/proc/$ppid/comm"
 	case $name in
-		*sh) ;;
-		"${0##*/}") ;;
-		*[Ll]ogin*|*init*) term=linux;;
-		*) term="$name";;
+		*sh|"${0##*/}") ;;  # skip shells
+		*[Ll]ogin*|*init*) break;;  # exit when the top is reached
+		*) term="$name"  # anything else can be assumed to be the terminal
 	esac
 done
 
 ## WM/DE
+# standard variables, mostly used for DEs
 if [ "$XDG_CURRENT_DESKTOP" ]; then
 	wm="$XDG_CURRENT_DESKTOP"
 elif [ "$DESKTOP_SESSION" ]; then
 	wm="$DESKTOP_SESSION"
 elif [ "$DISPLAY" ]; then
+	# non-standard WMs
+	# loop over all processes and check the binary name
 	for i in /proc/*/comm; do
 		read -r c < "$i"
 		case $c in
@@ -40,16 +48,15 @@ elif [ "$DISPLAY" ]; then
 fi
 
 ## Distro
-. /etc/os-release   # lol EZ
+. /etc/os-release   # a common file that has variables about the distro
 
 ## Memory
+# loop over lines in /proc/meminfo until it reaches MemTotal,
+# then convert the amount (second word) from KB to MB
 while read -r line; do
-	case $line in
-		MemTotal*) mem="${line##*: }"; break;;
-	esac
+	_ "$line" "MemTotal*" && set -- $line && break
 done < /proc/meminfo
-mem="${mem##*  }"
-mem="$(( ${mem%% *} / 1000 ))"
+mem="$(( $2 / 1000 ))MB"
 
 ## Processor
 while read -r line; do
@@ -60,7 +67,7 @@ while read -r line; do
 done < /proc/cpuinfo
 vendor="${vendor##*Authentic}"
 vendor="${vendor##*Genuine}"
-# This is so messy due to so many inconsistencies in the model names
+# this is so messy due to so many inconsistencies in the model names
 cpu="${cpu##*) }"
 cpu="${cpu%% @*}"
 cpu="${cpu%% CPU}"
@@ -79,25 +86,24 @@ up=$(printf %02d:%02d $((uptime / 60 / 60 % 24)) $((uptime / 60 % 60)))
 ## Kernel
 read -r _ _ version _ < /proc/version
 kernel="${version%%-*}"
-case $version in
-	*Microsoft*) [ "$ID" ] && ID="fake $ID";;
-esac
+_ "$version" "*Microsoft*" && ID="fake $ID"
 
 ## GTK
 while read -r line; do
-	case $line in
-		gtk-theme*) gtk="${line##*=}"; break;;
-	esac
+	_ "$line" "gtk-theme*" && gtk="${line##*=}" && break
 done < "${XDG_CONFIG_HOME:-$HOME/.config}"/gtk-3.0/settings.ini
 
 ## Motherboard // laptop
 read -r model < /sys/devices/virtual/dmi/id/product_name
 
 ## Packages
-[ -d /var/lib/pacman/local ] && set -- /var/lib/pacman/local/*
-[ -d /var/db/xbps ] && set -- /var/db/xbps/.*
-[ -d /var/db/pkg ] && set -- /var/db/pkg/*/*
+# clean environment, then make every file in the dir an argument,
+# then save the argument count to $pkgs
+set --
 [ -d /var/db/kiss/installed ] && set -- /var/db/kiss/installed/*
+[ -d /var/lib/pacman/local  ] && set -- /var/lib/pacman/local/*
+[ -d /var/db/xbps ] && set -- /var/db/xbps/.*
+[ -d /var/db/pkg  ] && set -- /var/db/pkg/*/*  # gentoo
 [ $# -gt 0 ] && pkgs=$#
 
 col() {
@@ -115,7 +121,10 @@ print() {
 
 read -r host < /proc/sys/kernel/hostname
 
-for i in ${info:-n user os sh wm up gtk cpu mem host kern pkgs term col n}; do
+# default value
+: "${info:=n user os sh wm up gtk cpu mem host kern pkgs term col n}"
+
+for i in $info; do
 	case $i in
 		n) echo;;
 		os) print os "$ID";;
@@ -124,7 +133,7 @@ for i in ${info:-n user os sh wm up gtk cpu mem host kern pkgs term col n}; do
 		up) print up "$up";;
 		gtk) print gtk "${gtk# }";;
 		cpu) print cpu "$vendor $cpu";;
-		mem) print mem "${mem}MB";;
+		mem) print mem "$mem";;
 		host) print host "$model";;
 		kern) print kern "$kernel";;
 		pkgs) print pkgs "$pkgs";;