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The Android Shell

OP Mohamed Nagy

10th June 2014, 10:13 AM   |  #1  
OP Junior Member
Thanks Meter: 8
 
14 posts
Join Date:Joined: Apr 2014
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.
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