Add a README.md about our shell and utilities.
This is definitely a FAQ, and it doesn't make sense for me to maintain
this on Google+ when I have the power to just check it in (and now have
a sensible place to do so).
Bug: N/A
Test: N/A
Change-Id: I649803ac846917a45f4b7b89cffe5b450179c479
diff --git a/shell_and_utilities/README.md b/shell_and_utilities/README.md
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+Android's shell and utilities
+=============================
+
+Since IceCreamSandwich Android has used
+[mksh](https://www.mirbsd.org/mksh.htm) as its shell. Before then it used
+[ash](https://en.wikipedia.org/wiki/Almquist_shell) (which actually
+remained in the tree up to and including KitKat).
+
+Initially Android had a very limited command-line provided by its
+own "toolbox" binary. These days almost everything is supplied by
+[toybox](http://landley.net/toybox/) instead.
+
+We started moving a few of the more important tools to full
+BSD implementations in JellyBean before we started in earnest in
+Lollipop. Lollipop was a major break with the past in many ways (LP64
+support and the switch to ART both having lots of knock-on effects around
+the system), so although this was the beginning of the end of toolbox it
+(a) didn't stand out given all the other systems-level changes and (b)
+in Marshmallow we changed direction and started the move to toybox.
+
+The lists below show what tools were provided and where they came from in
+each release starting with Gingerbread. This doesn't tell the full story,
+because the toolbox implementations did have bugs fixed and options added
+over the years. Gingerbread's rm, for example, supported `-r`/`-R` but not
+`-f`. But this gives you an idea of what was available in any given release,
+and how usable it was likely to be.
+
+
+Android 2.3 (Gingerbread)
+-------------------------
+
+BSD: cat dd newfs\_msdos
+
+toolbox: chmod chown cmp date df dmesg getevent getprop hd id ifconfig
+iftop insmod ioctl ionice kill ln log ls lsmod lsof mkdir mount mv
+nandread netstat notify printenv ps reboot renice rm rmdir rmmod route
+schedtop sendevent setconsole setprop sleep smd start stop sync top
+umount uptime vmstat watchprops wipe
+
+
+Android 4.0 (IceCreamSandwich)
+------------------------------
+
+BSD: cat dd newfs\_msdos
+
+toolbox: chmod chown cmp date df dmesg getevent getprop hd id ifconfig
+iftop insmod ioctl ionice kill ln log ls lsmod lsof mkdir mount mv
+nandread netstat notify printenv ps reboot renice rm rmdir rmmod route
+schedtop sendevent setconsole setprop sleep smd start stop sync top
+touch umount uptime vmstat watchprops wipe
+
+
+Android 4.1-4.3 (JellyBean)
+---------------------------
+
+BSD: cat cp dd du grep newfs\_msdos
+
+toolbox: chcon chmod chown clear cmp date df dmesg getenforce getevent
+getprop getsebool hd id ifconfig iftop insmod ioctl ionice kill ln
+load\_policy log ls lsmod lsof md5 mkdir mount mv nandread netstat notify
+printenv ps reboot renice restorecon rm rmdir rmmod route runcon schedtop
+sendevent setconsole setenforce setprop setsebool sleep smd start stop
+sync top touch umount uptime vmstat watchprops wipe
+
+
+Android 4.4 (KitKat)
+--------------------
+
+BSD: cat cp dd du grep newfs\_msdos
+
+toolbox: chcon chmod chown clear cmp date df dmesg getenforce getevent
+getprop getsebool hd id ifconfig iftop insmod ioctl ionice kill ln
+load\_policy log ls lsmod lsof md5 mkdir mkswap mount mv nandread netstat
+notify printenv ps readlink renice restorecon rm rmdir rmmod route runcon
+schedtop sendevent setconsole setenforce setprop setsebool sleep smd start
+stop swapoff swapon sync top touch umount uptime vmstat watchprops wipe
+
+
+Android 5.0 (Lollipop)
+----------------------
+
+BSD: cat chown cp dd du grep kill ln mv printenv rm rmdir sleep sync
+
+toolbox: chcon chmod clear cmp date df dmesg getenforce getevent getprop
+getsebool hd id ifconfig iftop insmod ioctl ionice load\_policy log ls
+lsmod lsof md5 mkdir mknod mkswap mount nandread netstat newfs\_msdos
+nohup notify ps readlink renice restorecon rmmod route runcon schedtop
+sendevent setenforce setprop setsebool smd start stop swapoff swapon
+top touch umount uptime vmstat watchprops wipe
+
+
+Android 6.0 (Marshmallow)
+-------------------------
+
+BSD: dd du grep
+
+toolbox: df getevent iftop ioctl ionice log ls lsof mount nandread
+newfs\_msdos ps prlimit renice sendevent start stop top uptime watchprops
+
+toybox: acpi basename blockdev bzcat cal cat chcon chgrp chmod chown
+chroot cksum clear comm cmp cp cpio cut date dirname dmesg dos2unix echo
+env expand expr fallocate false find free getenforce getprop groups
+head hostname hwclock id ifconfig inotifyd insmod kill load\_policy ln
+logname losetup lsmod lsusb md5sum mkdir mknod mkswap mktemp modinfo
+more mountpoint mv netstat nice nl nohup od paste patch pgrep pidof
+pkill pmap printenv printf pwd readlink realpath restorecon rm rmdir
+rmmod route runcon sed seq setenforce setprop setsid sha1sum sleep sort
+split stat strings swapoff swapon sync sysctl tac tail tar taskset tee
+time timeout touch tr true truncate umount uname uniq unix2dos usleep
+vmstat wc which whoami xargs yes
+
+
+Android 7.0 (Nougat)
+--------------------
+
+BSD: dd grep
+
+toolbox: getevent iftop ioctl log nandread newfs\_msdos ps prlimit
+sendevent start stop top
+
+toybox: acpi base64 basename blockdev bzcat cal cat chcon chgrp chmod
+chown chroot cksum clear comm cmp cp cpio cut date df dirname dmesg
+dos2unix du echo env expand expr fallocate false find flock free
+getenforce getprop groups head hostname hwclock id ifconfig inotifyd
+insmod ionice iorenice kill killall load\_policy ln logname losetup ls
+lsmod lsof lsusb md5sum mkdir mknod mkswap mktemp modinfo more mount
+mountpoint mv netstat nice nl nohup od paste patch pgrep pidof pkill
+pmap printenv printf pwd readlink realpath renice restorecon rm rmdir
+rmmod route runcon sed seq setenforce setprop setsid sha1sum sleep sort
+split stat strings swapoff swapon sync sysctl tac tail tar taskset tee
+time timeout touch tr true truncate tty ulimit umount uname uniq unix2dos
+uptime usleep vmstat wc which whoami xargs xxd yes
+
+
+Current AOSP
+------------
+
+BSD: dd grep
+
+bzip2: bzcat bzip2 bunzip2
+
+toolbox: getevent gzip newfs\_msdos gunzip zcat
+
+toybox: acpi base64 basename blockdev cal cat chcon chgrp chmod chown
+chroot chrt cksum clear cmp comm cp cpio cut date df diff dirname dmesg
+dos2unix du echo env expand expr fallocate false file find flock free
+getenforce getprop groups head hostname hwclock id ifconfig inotifyd
+insmod ionice iorenice kill killall ln load\_policy log logname losetup
+ls lsmod lsof lsusb md5sum microcom mkdir mknod mkswap mktemp modinfo
+modprobe more mount mountpoint mv netstat nice nl nohup od paste patch
+pgrep pidof pkill pmap printenv printf ps pwd readlink realpath renice
+restorecon rm rmdir rmmod runcon sed sendevent seq setenforce setprop
+setsid sha1sum sha224sum sha256sum sha384sum sha512sum sleep sort split
+start stat stop strings swapoff swapon sync sysctl tac tail tar taskset
+tee time timeout top touch tr true truncate tty ulimit umount uname uniq
+unix2dos uptime usleep uudecode uuencode vmstat wc which whoami xargs
+xxd yes