From: Andre Noll <maan@systemlinux.org>
Date: Thu, 29 Sep 2011 13:12:33 +0000 (+0200)
Subject: gsu: Overhaul of the rexexp matching for help commands.
X-Git-Url: http://git.tuebingen.mpg.de/?p=gsu.git;a=commitdiff_plain;h=45ca1b29b59a43524fb3ad6a013c5705ad3bdbde

gsu: Overhaul of the rexexp matching for help commands.

The old sed scripts were unreadable and broken on non-gnu systems
since they made use of some gnuisms of grep and sed like \+ in regular
expressions to match at least one character or sed's T command which
jumps to a label if no substitution has been made since the most
recent reading of an input line.

This patch switches to extended regular expressions and replaces all
broken sed scripts by portable ones, which are known to work at least
on FreeBSD and MacOS. The new scripts are commented verbosely so that
any subsequent changes do not require a full rewrite, hopefully.
---

diff --git a/misc/gsu/subcommand b/misc/gsu/subcommand
index f5f4745..a688ed5 100644
--- a/misc/gsu/subcommand
+++ b/misc/gsu/subcommand
@@ -11,16 +11,33 @@ _gsu_usage()
 	gsu_short_msg "# Usage: $_gsu_self command [options]"
 }
 
-# Each line matching this is recognized as a subcommand. The name
-# of the subcommand is the first subexpression.
-export gsu_command_regex='^com_\([-a-zA-Z_0-9]\+\)()'
+# Each line matching this is recognized as a subcommand. The name of the may be
+# given as $1. In any case the subcommand is the first subexpression.
+_gsu_get_command_regex()
+{
+	local cmd="${1:-[-a-zA-Z_0-9]+}"
+	result="^com_($cmd)\(\)"
+}
 
 _gsu_available_commands()
 {
+	local ere
+
+	_gsu_get_command_regex
+	ere="$result"
 	result="$({
 		printf "help\nman\nprefs\ncomplete\n"
-		sed -ne "s/$gsu_command_regex/\1/g;T;p" $0
-		} | sort | tr '\n' ' ')"
+		sed -Ee '
+			# if line matches, isolate command name
+			s/'"$ere"'/\1/g
+
+			# if there is a match, (print it and) start next cycle
+			t
+
+			# otherwise delete it
+			d
+		' $0
+	} | sort | tr '\n' ' ')"
 }
 
 _gsu_print_available_commands()
@@ -194,7 +211,11 @@ was given.
 
 _com_help()
 {
-	local a b
+	local a b ere tab='	'
+
+	_gsu_get_command_regex
+	ere="$result"
+
 	if test -z "$1"; then
 		_gsu_banner_msg 2>&1
 		_gsu_usage 2>&1
@@ -203,21 +224,28 @@ _com_help()
 			printf "com_man()\n$gsu_man_txt" | head -n 4; echo "--"
 			printf "com_prefs()\n$gsu_prefs_txt" | head -n 4; echo "--"
 			printf "com_complete()\n$gsu_complete_txt" | head -n 4; echo "--"
-			grep -A 2 "$gsu_command_regex" $0
+			grep -EA 2 "$ere" $0
 		} | grep -v -- '--' \
-			| sed -e "/$gsu_command_regex/bs" \
-				-e 'H;$!d;x;s/\n//g;b' \
-				-e :s \
-				-e 'x;s/\n//g;${p;x;}' \
-			| sed -e "s/${gsu_command_regex}#*/\1\t/" \
-			| sort \
-			| while read a b; do
-				printf "$a\t"
-				if test ${#a} -lt 8; then
-					printf "\t"
-				fi
-				echo "$b"
-                        done
+			| sed -En "/$ere/"'!d
+				# remove everything but the command name
+				s/^com_(.*)\(\).*/\1/
+
+				# append tab after short commands (less than 8 chars)
+				s/^(.{1,7})$/\1'"$tab"'/g
+
+				# remove next line (should contain only ## anyway)
+				N
+				s/#.*//
+
+				# append next line, removing leading ##
+				N
+				s/#+ *//g
+
+				# replace newline by tab
+				y/\n/'"$tab"'/
+
+				# and print the sucker
+				p'
 		echo
 		echo "# Try $_gsu_self help <command> for info on <command>."
 		ret=$GSU_SUCCESS
@@ -244,13 +272,32 @@ _com_help()
 		return
 	fi
 	ret=$GSU_SUCCESS
-	if grep -q "^com_$1()" $0; then
-		sed -e "1,/^com_$1()$/d" -e '/^{/,$d' -e 's/^## *//' $0
+	_gsu_get_command_regex "$1"
+	ere="$result"
+	if ! grep -Eq "$ere" $0; then
+		_gsu_print_available_commands
+		result="$1"
+		ret=-$E_GSU_BAD_COMMAND
 		return
 	fi
-	_gsu_print_available_commands
-	result="$1"
-	ret=-$E_GSU_BAD_COMMAND
+	sed -nEe '
+		# only consider lines in the comment of the function
+		/'"$ere"'/,/^[^#]/ {
+
+			# remove leading ##
+			s/^## *//
+
+			# if it did start with ##, jump to label p and print it
+			tp
+
+			# otherwise, move on to next line
+			d
+
+			# print it
+			:p
+			p
+		}
+	' $0
 }
 
 complete_help()