[Galaxy Grand Duos i9082 Q&A, Help & Troubleshootin] Mohamed Nagy:
The Android Shell

A "shell" is a program that listens to keyboard input from a user and performs actions as directed by the user. Android devices come with a simple shell program. This shell program is mostly undocumented. Since many people are curious about it I thought I'd write up some documentation for it.

Currently this documentation is incomplete, sorry!

Common problems

The built-in shell has very limited error handling. When you type a command name incorrectly it will say "permission denied", even though the real problem is that it couldn't find the command:

$ dir

dir: permission denied <---- this is a misleading error message, should say 'dir: not found'

$ ls

... listing of current directory

The PATH variable

The Android shell will run any program it finds in its PATH. The PATH is a colon (':') seperated list of directories. You can find out what your shell's PATH is set to by using the built-in echo command:

$ echo $PATH

/data/local/bin:/sbin:/vendor/bin:/system/sbin:/system/bin:/system/xbin

Depending upon your shell, you may see a different result.

Built in Commands

Every shell has a few built-in commands. Some common built-in commands are:

echo -- prints text to stdout.

set -- sets shell variables

export -- makes shell variables available to command-line programs

cd -- change the current directory.

pwd -- print name of the current directory.

Commands

To find out what commands you have available to you, use the "ls" command on each of the directories in the PATH variable.

Finding documentation for the Android commands.

Many of the Android commands are based on standard Linux (or bsd) commands. If you're curious about a command, you can sometimes learn how it works by using the "man" command on a desktop Linux or OSX (Apple Macintosh) computer. The Linux or OSX version of the command may be different in details, but much of the documentation will still apply to the Android version of the command.

Another source of documentation for people without a Linux or OSX machine handy is to use a web browser and use a web search engine to search for the text: "man Linux command-name".

List of commands

The following is a list of the commands that are present on a Nexus S phone running an Android 2.3.3 "user-debug" build. Many of these commands are not present on a "user" phone. (They are missing from a "user" phone because they are specific to developing or debugging the Android operating system.)

$ ls /data/local/bin

/data/local/bin: No such file or directory

Notice that by default there is no /data/local/bin directory. You can create this directory using the "mkdir" command if you like.

$ ls /sbin

opendir failed, Permission denied

The /sbin directory exists, but you don't have permission to access it. You need root access. If you have a developer phone, or otherwise have root access to your phone you can see what's in this directory.

$ su

# ls /sbin

ueventd

adbd

# exit

$

Notice that the shell prompt changes from a '$' to a '#' to indicate that you have root access.

Notice also that neither of the /sbin commands are useful to the shell -- the adb and ueventd files are 'daemon' programs used to implement the Android Debugger "adb" program that is used by developers.

$ ls /vendor/bin

gpsd

pvrsrvinit

Vendor/bin is where device vendors can put device-specific executables. These files are from a Nexus S.

$ ls /system/sbin

/system/sbin: No such file or directory

This directory does not exist on a Nexus S.

$ ls /system/bin

am

am is the Android Activity Manager. It's used to start and stop Android activities (e.g. applications) from the command line. Type am by itself to get a list of options.

amix

aplay

Command line audio file player.

app_process

applypatch

Used to apply patches to android files.

arec

Command line audio recorder.

audioloop

bluetoothd

BlueTooth daemon

bmgr

Backup manager - type command by itself to get documentation.

bootanimation

Draws the boot animation. You may have to reset your phone to get out of this.

brcm_patchram_plus

bugreport

cat

Copy the contents of a file to standard output.

chmod

Change the mode of a file (e.g. whether it can be read or written.)

chown

Change the owner of a file.

cmp

Compare two files byte-by-byte

dalvikvm

The dalvik virtual machine. (Used to run Android applications.)

date

Prints the current date and time

dbus-daemon

dd

Convert and copy a file. By default copies standard in to standard out.

debuggerd

dexopt

df

Shows how much space is free on different file systems on your device.

dhcpcd

dmesg

dnsmasq

dumpstate

dumpsys

dvz

fsck_msdos

gdbserver

getevent

getprop

gzip

hciattach

hd

id

ifconfig

Shows the current configuration of network interfaces (IP, MAC address etc)

iftop

Shows the current processes using the network interfaces (top, but for networks)

ime

input

insmod

installd

ioctl

ionice

iptables

Manage the firewall

keystore

keystore_cli

kill

Send signals to processes.

linker

ln

Used to set up a file system link.

log

logcat

Prints the Android runtime log.

logwrapper

ls

Lists files.

lsmod

lsof

make_ext4fs

mediaserver

mkdir

Make a directory.

monkey

A program that sends random events, used to test applications. (Like having a monkey playing with the device.)

mount

mtpd

mv

Move a file from one directory to another. (Only on the same file system. Use "cat a > b" to copy a file between file systems.

nandread

ndc

netcfg

netd

netstat

newfs_msdos

notify

omx_tests

pand

ping

pm

pppd

printenv

ps

List active processes.

qemu-props

qemud

racoon

radiooptions

reboot

Reboot the device.

record

renice

rild

rm

Remove a file.

rmdir

Remove a directory.

rmmod

route

rtp_test

run-as

schedtest

schedtop

sdcard

sdptool

sendevent

service

servicemanager

setconsole

setprop

setup_fs

sh

showlease

sleep

smd

stagefright

start

Starts the Android runtime.

stop

Stops the Android runtime.

surfaceflinger

svc

sync

system_server

tc

testid3

toolbox

top

Shows which processes are currently using the most CPU time.

umount

uptime

Prints how long your device has been running since it was last booted.

vdc

vmstat

vold

watchprops

wipe

wpa_cli

wpa_supplicant

$ ls /system/xbin

add-property-tag

btool

check-lost+found

dexdump

dhdutil

hcidump

latencytop

librank

opcontrol

oprofiled

procmem

procrank

rawbu

scp

Secure copy program. (Used to copy files over the network.)

showmap

showslab

sqlite3

Used to administer SQLite databases.

strace

System trace command - use to see what system calls a program makes.

su

Start a shell with root privileges.

Versions of the Android Shell

Android 1.0 used a shell that had no tab completion or history editing.

Android 2.3 added history editing. You can for example use the up/down arrows to edit previous commands.