Treat custom and applet scripts as applets

BusyBox has support for embedded shell scripts.  Two types can be
distinguished:  custom scripts and scripts implementing applets.

Custom scripts should be placed in the 'embed' directory at build
time.  They are given a default applet configuration and appear
as applets to the user but no further configuration is possible.

Applet scripts are integrated with the BusyBox build system and
are intended to be used to ship standard applets that just happen
to be implemented as scripts.  They can be configured at build time
and appear just like native applets.

Such scripts should be placed in the 'applets_sh' directory.  A stub
C program should be written to provide the usual applet configuration
details and placed in a suitable subsystem directory.  It may be
helpful to have a configuration option to enable any dependencies the
script requires:  see the 'nologin' applet for an example.

function                                             old     new   delta
scripted_main                                          -      41     +41
applet_names                                        2773    2781      +8
applet_main                                         1600    1604      +4
i2cdetect_main                                       672     674      +2
applet_suid                                          100     101      +1
applet_install_loc                                   200     201      +1
applet_flags                                         100     101      +1
packed_usage                                       33180   33179      -1
tryexec                                              159     152      -7
evalcommand                                         1661    1653      -8
script_names                                           9       -      -9
packed_scripts                                       123     114      -9
complete_cmd_dir_file                                826     811     -15
shellexec                                            271     254     -17
find_command                                        1007     990     -17
busybox_main                                         642     624     -18
run_applet_and_exit                                  100      78     -22
find_script_by_name                                   51       -     -51
------------------------------------------------------------------------------
(add/remove: 1/2 grow/shrink: 6/9 up/down: 58/-174)          Total: -116 bytes
   text	   data	    bss	    dec	    hex	filename
 950034	    477	   7296	 957807	  e9d6f	busybox_old
 949918	    477	   7296	 957691	  e9cfb	busybox_unstripped

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

.gitignore

@@ -56,3 +56,8 @@ cscope.po.out
 #
 tags
 TAGS
+
+#
+# user-supplied scripts
+#
+/embed

Makefile

@@ -361,7 +361,7 @@ scripts/basic/%: scripts_basic ;
 
 # This target generates Kbuild's and Config.in's from *.c files
 PHONY += gen_build_files
-gen_build_files: $(wildcard $(srctree)/*/*.c) $(wildcard $(srctree)/*/*/*.c)
+gen_build_files: $(wildcard $(srctree)/*/*.c) $(wildcard $(srctree)/*/*/*.c) $(wildcard embed/*)
 	$(Q)$(srctree)/scripts/gen_build_files.sh $(srctree) $(objtree)
 
 # bbox: we have helpers in applets/
@@ -851,7 +851,7 @@ quiet_cmd_gen_common_bufsiz = GEN     include/common_bufsiz.h
 quiet_cmd_split_autoconf   = SPLIT   include/autoconf.h -> include/config/*
       cmd_split_autoconf   = scripts/basic/split-include include/autoconf.h include/config
 quiet_cmd_gen_embedded_scripts = GEN     include/embedded_scripts.h
-      cmd_gen_embedded_scripts = scripts/embedded_scripts include/embedded_scripts.h embed
+      cmd_gen_embedded_scripts = $(srctree)/scripts/embedded_scripts include/embedded_scripts.h $(srctree)/embed $(srctree)/applets_sh
 #bbox# piggybacked generation of few .h files
 include/config/MARKER: scripts/basic/split-include include/autoconf.h $(wildcard embed/*) scripts/embedded_scripts
 	$(call cmd,split_autoconf)

applets/busybox.mkscripts

@@ -0,0 +1,16 @@
+#!/bin/sh
+# Make busybox scripted applet list file.
+
+# input $1: full path to Config.h
+# input $2: full path to applets.h
+# output (stdout): list of pathnames that should be linked to busybox
+
+export LC_ALL=POSIX
+export LC_CTYPE=POSIX
+
+CONFIG_H=${1:-include/autoconf.h}
+APPLETS_H=${2:-include/applets.h}
+$HOSTCC -E -DMAKE_SCRIPTS -include $CONFIG_H $APPLETS_H |
+  awk '/^[ \t]*SCRIPT/{
+	print $2
+  }'

applets_sh/README

@@ -1,5 +0,0 @@
-This directory contains examples of applets implemented as shell scripts.
-
-So far these scripts are not hooked to the build system and are not
-installed by "make install". If you want to use them,
-you need to install them by hand.

applets_sh/dos2unix

@@ -1,5 +0,0 @@
-#!/bin/sh
-# TODO: use getopt to avoid parsing options as filenames,
-# and to support -- and --help
-[ $# -ne 0 ] && DASH_I=-i
-sed $DASH_I -e 's/\r$//' "$@"

applets_sh/nologin

@@ -0,0 +1,3 @@
+cat /etc/nologin.txt 2>/dev/null || echo This account is not available
+sleep 5
+exit 1

applets_sh/tac

@@ -1,7 +0,0 @@
-#!/bin/sh
-# TODO: use getopt to avoid parsing options as filenames,
-# and to support -- and --help
-for i in "$@"
-do
-sed -e '1!G;h;$!d' "$i"
-done

applets_sh/unix2dos

@@ -1,5 +0,0 @@
-#!/bin/sh
-# TODO: use getopt to avoid parsing options as filenames,
-# and to support -- and --help
-[ $# -ne 0 ] && DASH_I=-i
-sed $DASH_I -e 's/$/\r/' "$@"

embed/nologin

@@ -1,4 +0,0 @@
-#!/bin/sh
-cat /etc/nologin.txt 2>/dev/null || echo "This account is not available"
-sleep 5
-exit 1

include/applets.src.h

@@ -22,41 +22,60 @@ s     - suid type:
         BB_SUID_REQUIRE or BB_SUID_MAYBE applet.
 */
 
+#define NOUSAGE_STR "\b"
+
+#define dummy_trivial_usage NOUSAGE_STR \
+
+#define dummy_full_usage "" \
+
 #if defined(PROTOTYPES)
 # define APPLET(name,l,s)                    int name##_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 # define APPLET_ODDNAME(name,main,l,s,help)  int main##_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 # define APPLET_NOEXEC(name,main,l,s,help)   int main##_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 # define APPLET_NOFORK(name,main,l,s,help)   int main##_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+# define APPLET_SCRIPTED(name,main,l,s,help)
 
 #elif defined(NAME_MAIN)
 # define APPLET(name,l,s)                    name name##_main
 # define APPLET_ODDNAME(name,main,l,s,help)  name main##_main
 # define APPLET_NOEXEC(name,main,l,s,help)   name main##_main
 # define APPLET_NOFORK(name,main,l,s,help)   name main##_main
+# define APPLET_SCRIPTED(name,main,l,s,help) name scripted_main
 
 #elif defined(MAKE_USAGE) && ENABLE_FEATURE_VERBOSE_USAGE
 # define APPLET(name,l,s)                    MAKE_USAGE(#name, name##_trivial_usage name##_full_usage)
 # define APPLET_ODDNAME(name,main,l,s,help)  MAKE_USAGE(#name, help##_trivial_usage help##_full_usage)
 # define APPLET_NOEXEC(name,main,l,s,help)   MAKE_USAGE(#name, help##_trivial_usage help##_full_usage)
 # define APPLET_NOFORK(name,main,l,s,help)   MAKE_USAGE(#name, help##_trivial_usage help##_full_usage)
+# define APPLET_SCRIPTED(name,main,l,s,help) MAKE_USAGE(#name, help##_trivial_usage help##_full_usage)
 
 #elif defined(MAKE_USAGE) && !ENABLE_FEATURE_VERBOSE_USAGE
 # define APPLET(name,l,s)                    MAKE_USAGE(#name, name##_trivial_usage)
 # define APPLET_ODDNAME(name,main,l,s,help)  MAKE_USAGE(#name, help##_trivial_usage)
 # define APPLET_NOEXEC(name,main,l,s,help)   MAKE_USAGE(#name, help##_trivial_usage)
 # define APPLET_NOFORK(name,main,l,s,help)   MAKE_USAGE(#name, help##_trivial_usage)
+# define APPLET_SCRIPTED(name,main,l,s,help) MAKE_USAGE(#name, help##_trivial_usage)
 
 #elif defined(MAKE_LINKS)
 # define APPLET(name,l,c)                    LINK l name
 # define APPLET_ODDNAME(name,main,l,s,help)  LINK l name
 # define APPLET_NOEXEC(name,main,l,s,help)   LINK l name
 # define APPLET_NOFORK(name,main,l,s,help)   LINK l name
+# define APPLET_SCRIPTED(name,main,l,s,help) LINK l name
 
 #elif defined(MAKE_SUID)
 # define APPLET(name,l,s)                    SUID s l name
 # define APPLET_ODDNAME(name,main,l,s,help)  SUID s l name
 # define APPLET_NOEXEC(name,main,l,s,help)   SUID s l name
 # define APPLET_NOFORK(name,main,l,s,help)   SUID s l name
+# define APPLET_SCRIPTED(name,main,l,s,help) SUID s l name
+
+#elif defined(MAKE_SCRIPTS)
+# define APPLET(name,l,s)
+# define APPLET_ODDNAME(name,main,l,s,help)
+# define APPLET_NOEXEC(name,main,l,s,help)
+# define APPLET_NOFORK(name,main,l,s,help)
+# define APPLET_SCRIPTED(name,main,l,s,help) SCRIPT name
 
 #else
   static struct bb_applet applets[] = { /*    name, main, location, need_suid */
@@ -64,6 +83,7 @@ s     - suid type:
 # define APPLET_ODDNAME(name,main,l,s,help)  { #name, #main, l, s },
 # define APPLET_NOEXEC(name,main,l,s,help)   { #name, #main, l, s, 1 },
 # define APPLET_NOFORK(name,main,l,s,help)   { #name, #main, l, s, 1, 1 },
+# define APPLET_SCRIPTED(name,main,l,s,help) { #name, #main, l, s },
 #endif
 
 #if ENABLE_INSTALL_NO_USR
@@ -84,3 +104,4 @@ INSERT
 #undef APPLET_ODDNAME
 #undef APPLET_NOEXEC
 #undef APPLET_NOFORK
+#undef APPLET_SCRIPTED

include/libbb.h

@@ -1322,8 +1322,8 @@ void bb_logenv_override(void) FAST_FUNC;
 #endif
 
 /* Embedded script support */
-int find_script_by_name(const char *name) FAST_FUNC;
 char *get_script_content(unsigned n) FAST_FUNC;
+int scripted_main(int argc, char** argv);
 
 /* Applets which are useful from another applets */
 int bb_cat(char** argv) FAST_FUNC;

libbb/appletlib.c

@@ -51,7 +51,7 @@
 #include "usage_compressed.h"
 
 #if ENABLE_ASH_EMBEDDED_SCRIPTS
-# define DEFINE_script_names 1
+# define DEFINE_SCRIPT_DATA 1
 # include "embedded_scripts.h"
 #else
 # define NUM_SCRIPTS 0
@@ -818,27 +818,21 @@ int busybox_main(int argc UNUSED_PARAM, char **argv)
 		/* prevent last comma to be in the very last pos */
 		output_width--;
 		a = applet_names;
-		{
+		while (*a) {
-#  if NUM_SCRIPTS > 0
+			int len2 = strlen(a) + 2;
-			int i;
+			if (col >= (int)output_width - len2) {
-			for (i = 0; i < 2; i++, a = script_names)
+				full_write2_str(",\n");
-#  endif
+				col = 0;
-			while (*a) {
-				int len2 = strlen(a) + 2;
-				if (col >= (int)output_width - len2) {
-					full_write2_str(",\n");
-					col = 0;
-				}
-				if (col == 0) {
-					col = 6;
-					full_write2_str("\t");
-				} else {
-					full_write2_str(", ");
-				}
-				full_write2_str(a);
-				col += len2;
-				a += len2 - 1;
 			}
+			if (col == 0) {
+				col = 6;
+				full_write2_str("\t");
+			} else {
+				full_write2_str(", ");
+			}
+			full_write2_str(a);
+			col += len2;
+			a += len2 - 1;
 		}
 		full_write2_str("\n");
 		return 0;
@@ -946,20 +940,25 @@ void FAST_FUNC run_applet_no_and_exit(int applet_no, const char *name, char **ar
 # endif /* NUM_APPLETS > 0 */
 
 # if NUM_SCRIPTS > 0
-int FAST_FUNC
+static int find_script_by_name(const char *name)
-find_script_by_name(const char *name)
 {
-	const char *s = script_names;
+	int i;
-	int i = 0;
+	int applet = find_applet_by_name(name);
 
-	while (*s) {
+	if (applet >= 0) {
-		if (strcmp(name, s) == 0)
+		for (i = 0; i < NUM_SCRIPTS; ++i)
-			return i;
+			if (applet_numbers[i] == applet)
-		i++;
+				return i;
-		while (*s++ != '\0')
-			continue;
 	}
-	return -0x10000; /* make it so that NUM_APPLETS + <error> is still < 0 */
+	return -1;
+}
+
+int scripted_main(int argc UNUSED_PARAM, char **argv)
+{
+	int script = find_script_by_name(applet_name);
+	if (script >= 0)
+		exit(ash_main(-script - 1, argv));
+	return 0;
 }
 
 char* FAST_FUNC
@@ -978,7 +977,7 @@ get_script_content(unsigned n)
 }
 # endif /* NUM_SCRIPTS > 0 */
 
-# if ENABLE_BUSYBOX || NUM_APPLETS > 0 || NUM_SCRIPTS > 0
+# if ENABLE_BUSYBOX || NUM_APPLETS > 0
 static NORETURN void run_applet_and_exit(const char *name, char **argv)
 {
 #  if ENABLE_BUSYBOX
@@ -993,13 +992,6 @@ static NORETURN void run_applet_and_exit(const char *name, char **argv)
 			run_applet_no_and_exit(applet, name, argv);
 	}
 #  endif
-#  if NUM_SCRIPTS > 0
-	{
-		int script = find_script_by_name(name);
-		if (script >= 0)
-			exit(ash_main(-script - 1, argv));
-	}
-#  endif
 
 	/*bb_error_msg_and_die("applet not found"); - links in printf */
 	full_write2_str(applet_name);

libbb/lineedit.c

@@ -41,12 +41,6 @@
 #include "busybox.h"
 #include "NUM_APPLETS.h"
 #include "unicode.h"
-#if ENABLE_ASH_EMBEDDED_SCRIPTS
-# include "embedded_scripts.h"
-#else
-# define NUM_SCRIPTS 0
-#endif
-
 #ifndef _POSIX_VDISABLE
 # define _POSIX_VDISABLE '\0'
 #endif
@@ -812,20 +806,14 @@ static NOINLINE unsigned complete_cmd_dir_file(const char *command, int type)
 	}
 	pf_len = strlen(pfind);
 
-# if ENABLE_FEATURE_SH_STANDALONE && (NUM_APPLETS != 1 || NUM_SCRIPTS > 0)
+# if ENABLE_FEATURE_SH_STANDALONE && NUM_APPLETS != 1
 	if (type == FIND_EXE_ONLY && !dirbuf) {
-		const char *p;
+		const char *p = applet_names;
-#  if NUM_APPLETS != 1 && NUM_SCRIPTS > 0
+
-		for (i = 0, p = applet_names; i < 2; i++, p = script_names)
-#  elif NUM_APPLETS != 1 /* and NUM_SCRIPTS == 0 */
-		p = applet_names;
-#  else /* NUM_APPLETS == 1 && NUM_SCRIPTS > 0 */
-		p = script_names;
-#  endif
 		while (*p) {
 			if (strncmp(pfind, p, pf_len) == 0)
 				add_match(xstrdup(p));
-			while (*p++)
+			while (*p++ != '\0')
 				continue;
 		}
 	}

scripts/embedded_scripts

@@ -1,7 +1,8 @@
 #!/bin/sh
 
 target="$1"
-loc="$2"
+custom_loc="$2"
+applet_loc="$3"
 
 test "$target" || exit 1
 test "$SED" || SED=sed
@@ -14,46 +15,102 @@ if test $? != 0; then
 	exit 1
 fi
 
-exec >"$target.$$"
+custom_scripts=""
-
+if [ -d "$custom_loc" ]
-scripts=""
-if [ -d "$loc" ]
 then
-	scripts=$(cd $loc; ls * 2>/dev/null)
+	custom_scripts=$(cd $custom_loc; ls * 2>/dev/null)
+fi
+all_scripts=$(applets/busybox.mkscripts)
+
+# all_scripts includes applet scripts and custom scripts, sort them out
+applet_scripts=""
+for i in $all_scripts
+do
+    found=0
+	for j in $custom_scripts
+	do
+		if [ "$i" = "$j" ]
+		then
+			found=1
+			break;
+		fi
+	done
+	if [ $found -eq 0 ]
+	then
+		# anything that isn't a custom script is an applet script
+		applet_scripts="$applet_scripts $i"
+	fi
+done
+
+# we know the custom scripts are present but applet scripts might have
+# become detached from their configuration
+for i in $applet_scripts
+do
+	#if [ ! -f "$applet_loc/$i" -a ! -f "$custom_loc/$i" ]
+	if [ ! -f "$applet_loc/$i" ]
+	then
+		echo "missing applet script $i"
+		exit 1
+	fi
+done
+
+n=$(echo $custom_scripts $applet_scripts | wc -w)
+nall=$(echo $all_scripts | wc -w)
+
+if [ $n -ne $nall ]
+then
+	echo "script mismatch $n != $nall"
+	exit 1
 fi
 
-n=$(echo $scripts | wc -w)
+concatenate_scripts() {
+	for i in $custom_scripts
+	do
+		cat $custom_loc/$i
+		printf '\000'
+	done
+	for i in $applet_scripts
+	do
+		cat $applet_loc/$i
+		printf '\000'
+	done
+}
+
+exec >"$target.$$"
 
 if [ $n -ne 0 ]
 then
-	printf '#ifdef DEFINE_script_names\n'
+	printf '#ifdef DEFINE_SCRIPT_DATA\n'
-	printf 'const char script_names[] ALIGN1 = '
+	if [ $n -ne 0 ]
-	for i in $scripts
+	then
-	do
+		printf 'const uint16_t applet_numbers[] = {\n'
-		printf '"%s\\0"' $i
+		for i in $custom_scripts $applet_scripts
-	done
+		do
-	printf ';\n'
+			# TODO support applets with names including invalid characters
+			printf '\tAPPLET_NO_%s,\n' $i
+		done
+		printf '};\n'
+	fi
 	printf '#else\n'
-	printf 'extern const char script_names[] ALIGN1;\n'
+	if [ $n -ne 0 ]
+	then
+		printf 'extern const uint16_t applet_numbers[];\n'
+	fi
 	printf '#endif\n'
 fi
-printf "#define NUM_SCRIPTS $n\n\n"
+
+printf "\n"
+printf '#define NUM_SCRIPTS %d\n' $n
+printf "\n"
 
 if [ $n -ne 0 ]
 then
 	printf '#define UNPACKED_SCRIPTS_LENGTH '
-	for i in $scripts
+	concatenate_scripts | wc -c
-	do
-		cat $loc/$i
-		printf '\000'
-	done | wc -c
 
 	printf '#define PACKED_SCRIPTS \\\n'
-	for i in $scripts
+	concatenate_scripts | bzip2 -1 | $DD bs=2 skip=1 2>/dev/null | \
-	do
+	od -v -b \
-		cat $loc/$i
-		printf '\000'
-	done | bzip2 -1 | $DD bs=2 skip=1 2>/dev/null | od -v -b \
 	| grep -v '^ ' \
 	| $SED -e 's/^[^ ]*//' \
 		-e 's/ //g' \

scripts/gen_build_files.sh

@@ -17,12 +17,26 @@ status() { printf '  %-8s%s\n' "$1" "$2"; }
 gen() { status "GEN" "$@"; }
 chk() { status "CHK" "$@"; }
 
+# scripts in the 'embed' directory are treated as fake applets
+custom_scripts()
+{
+	custom_loc="$1"
+	if [ -d "$custom_loc" ]
+	then
+		for i in $(cd "$custom_loc"; ls *)
+		do
+			printf "APPLET_SCRIPTED(%s, scripted, BB_DIR_USR_BIN, BB_SUID_DROP, dummy)\n" $i;
+		done
+	fi
+}
+
 generate()
 {
 	# NB: data to be inserted at INSERT line is coming on stdin
 	src="$1"
 	dst="$2"
 	header="$3"
+	loc="$4"
 	#chk "${dst}"
 	{
 		# Need to use printf: different shells have inconsistent
@@ -32,6 +46,10 @@ generate()
 		sed -n '/^INSERT$/ q; p' "${src}"
 		# copy stdin to stdout
 		cat
+		if [ -n "$loc" ]
+		then
+			custom_scripts "$loc"
+		fi
 		# print everything after INSERT line
 		sed -n '/^INSERT$/ {
 		:l
@@ -53,7 +71,8 @@ sed -n 's@^//applet:@@p' "$srctree"/*/*.c "$srctree"/*/*/*.c \
 | generate \
 	"$srctree/include/applets.src.h" \
 	"include/applets.h" \
-	"/* DO NOT EDIT. This file is generated from applets.src.h */"
+	"/* DO NOT EDIT. This file is generated from applets.src.h */" \
+	"$srctree/embed"
 
 # (Re)generate include/usage.h
 # We add line continuation backslash after each line,

shell/ash.c

@@ -158,6 +158,10 @@
 //config:	at build time. Like applets, scripts can be run as
 //config:	'busybox SCRIPT ...' or by linking their name to the binary.
 //config:
+//config:	This also allows applets to be implemented as scripts: place
+//config:	the script in 'applets_sh' and a stub C file containing
+//config:	configuration in the appropriate subsystem directory.
+//config:
 //config:endif # ash options
 
 //applet:IF_ASH(APPLET(ash, BB_DIR_BIN, BB_SUID_DROP))
@@ -8016,9 +8020,6 @@ tryexec(IF_FEATURE_SH_STANDALONE(int applet_no,) const char *cmd, char **argv, c
 {
 #if ENABLE_FEATURE_SH_STANDALONE
 	if (applet_no >= 0) {
-# if NUM_SCRIPTS > 0
-		if (applet_no < NUM_APPLETS)
-# endif
 		if (APPLET_IS_NOEXEC(applet_no)) {
 			clearenv();
 			while (*envp)
@@ -8088,9 +8089,6 @@ static void shellexec(char *prog, char **argv, const char *path, int idx)
 	if (strchr(prog, '/') != NULL
 #if ENABLE_FEATURE_SH_STANDALONE
 	 || (applet_no = find_applet_by_name(prog)) >= 0
-# if NUM_SCRIPTS > 0
-	 || (applet_no = NUM_APPLETS + find_script_by_name(prog)) >= 0
-# endif
 #endif
 	) {
 		tryexec(IF_FEATURE_SH_STANDALONE(applet_no,) prog, argv, envp);
@@ -10192,10 +10190,6 @@ evalcommand(union node *cmd, int flags)
  */
 		/* find_command() encodes applet_no as (-2 - applet_no) */
 		int applet_no = (- cmdentry.u.index - 2);
-# if NUM_SCRIPTS > 0
-		/* Applets are ok, but not embedded scripts */
-		if (applet_no < NUM_APPLETS)
-# endif
 		if (applet_no >= 0 && APPLET_IS_NOFORK(applet_no)) {
 			char **sv_environ;
 
@@ -13378,11 +13372,6 @@ find_command(char *name, struct cmdentry *entry, int act, const char *path)
 #if ENABLE_FEATURE_SH_STANDALONE
 	{
 		int applet_no = find_applet_by_name(name);
-# if NUM_SCRIPTS > 0
-		if (applet_no < 0)
-			/* embedded script indices are offset by NUM_APPLETS */
-			applet_no = NUM_APPLETS + find_script_by_name(name);
-# endif
 		if (applet_no >= 0) {
 			entry->cmdtype = CMDNORMAL;
 			entry->u.index = -2 - applet_no;

util-linux/nologin.c

@@ -0,0 +1,27 @@
+//config:config NOLOGIN
+//config:	bool "nologin"
+//config:	default y
+//config:	depends on ASH_EMBEDDED_SCRIPTS
+//config:	help
+//config:	Politely refuse a login
+//config:
+//config:config NOLOGIN_DEPENDENCIES
+//config:	bool "Dependencies for nologin"
+//config:	default y
+//config:	depends on NOLOGIN
+//config:	select CAT
+//config:	select ECHO
+//config:	select SLEEP
+//config:	help
+//config:	nologin is implemented as a shell script. It requires the
+//config:	following in the runtime environment:
+//config:		cat echo sleep
+//config:	If you know these will be available externally you can
+//config:	disable this option.
+
+//applet:IF_NOLOGIN(APPLET_SCRIPTED(nologin, scripted, BB_DIR_USR_SBIN, BB_SUID_DROP, nologin))
+
+//usage:#define nologin_trivial_usage
+//usage:	""
+//usage:#define nologin_full_usage "\n\n"
+//usage:	"Politely refuse a login"