Develop Reference

linux shell - can't compare strings with: adb shell getprop ro.product.brand

This is really odd...
I can't get this test to result in true in my linux shell and I can't figure out why.
#!/bin/bash
a=$(adb shell getprop ro.product.brand)
adb shell getprop ro.product.brand
if [ "$a" == "Huawei" ]; then
echo "Success"
else
echo "Failed"
fi
The script just outputs:
Huawei
Failed
Whereas this script:
b=$(whoami)
whoami
if [ "$b" == "amo" ]; then
echo "Success"
else
echo "Failed"
fi
...outputs:
amo
Success
Can anyone help me understand that?
I already tried cutting away spaces or line breaks in $a by piping to cut or sed but I get the same result...

I suggest this as a way to remove leading/trailing whitespace :
# Trims $1
# If $2 supplied, assigns result to variable named $2
# If $2 not present, echoes the value to stdout
trim()
{
if
[[ $1 =~ ^[[:blank:]]*(.*[^[:blank:]])[[:blank:]]*$ ]]
then
local result="${BASH_REMATCH[1]}"
else
local result="$1"
fi
if
(( $# > 1 ))
then
printf -v "$2" %s "$result"
else
printf %s "$result"
fi
}
This function uses no external program, so has low overhead.
Maybe a quick explanation of the regular expression...
^[[:blank:]]*(.*[^[:blank:]])[[:blank:]]*$
It matches all leading and trailing whitespace (no surprise there)
In the middle, it matches any string of characters that ends with a non-blank and saves that as a sub-expression for access with BASH_REMATCH
If there were no "non-blank" character specified to end the middle portion, the greedy .* would eat everything up until the end of the string, including trailing blanks.
The .* is, on the other hand, certain to begin with a non-blank, because the greedy initial [[:blank:]]* will only stop when encountering a non-blank.
Depending on your need, you may also use [[:space:]] instead of [[:blank:]] (difference explained here : https://en.wikipedia.org/wiki/Regular_expression#Character_classes). Basically, [[:blank:]] matches tabs and spaces, and [[:space:]] also matches newlines, carriage returns, and a few more.

Android: init.d script to monitor and kill a process

I'm running stock android (5.1.1) on my nexus 5 and trying to use a script to kill a process (kill_process.sh).
while true; do
PROCESS=$(pgrep -l whatsapp)
if [[ $PROCESS == *"whatsapp"* ]]; then
kill $(pgrep -f whatsapp)
fi
done
I'm able to have scripts running at boot using the app "Universal Init.d", but this particular script does not seem to be working at boot. It does work as long as I ssh into my phone and run it manually. E.g., as soon as I launch whatsapp it's being killed right away.
Does anybody have any ideas what I could do to make it work at boot?
Also, a while loop is probably not the most efficient way to do this...so any ideas are welcome.
Edit1:
changed the if statement to
case $PROCESS in *"whatsapp"*)
kill $(pgrep -f whatsapp)
esac
Edit2: is there a way to daemonize a script?
Edit3: I set up another script containing only one line start-stop-daemon --exec /path_to_main_script/kill_process.sh -S. I only put the new script in the /system/etc/init.d directory and the kill_process.sh script into a different subdirectory in /system/etc/. This way the new script is being run at boot which then calls the kill_process.sh script. But it's not running stable, which is caused by the "Universal Init.d" app: when the app crashes the script stops running. Any ideas?

Disclaimer: I never used the app Universal Init.d nor do I have a lot of Android experience. But I did some tests on my desktop:
me:~$ bash -x /tmp/x
+ a=abcd
+ [[ abcd == *bc* ]]
+ echo 0
0 # correct
me:~$ dash -x /tmp/x
+ a=abcd
+ [[ abcd == *bc* ]]
/tmp/x: 3: /tmp/x: [[: not found
+ echo 127
127 # [[ not supported
me:~$ busybox sh -x /tmp/x
+ a=abcd
+ [[ abcd == *bc* ]]
+ echo 1
1 # wrong!
The script:
a=abcd
[[ $a == *bc* ]]
echo $?
Conclusion: You should check the shell which the app uses. It's likely that the [[ syntax in combination with * fails. I think it's busybox or dash there...
For saving you battery, I recommend at least replacing while true by
while sleep 1; do
But also this is just a hack. You should look for an event-based solution (cannot help you there)

adb shell regular expression doesn't work as tested locally

First, sorry if my question is obscure or in an inconvenient format. This is my first post here :D.
My issue is that I have a script, let's say test.sh which reads an input, and validates if it's a positive integer (reg ex used from this post:
BASH: Test whether string is valid as an integer?):
#!/bin/sh
echo -n " enter number <"
read num
if [[ $num =~ ^-?[0-9]+$ ]] #if num contains any symbols/letters
then # anywhere in the string
echo "not a positive int"
exit
else
echo "positive int read"
fi
I am running this script on my android device (Xiaomi Mi3 w) using adb shell and the error:
syntax error: =~ unexpected operator keeps displaying.
First, is my regex even correct?
Second, any hints on how I can overcome this syntax error?

The default shell in Android is mksh. It is not 100% compatible with bash. So do not expect all bash recipes to work without changes.
For the description of features supported by mksh - read its manual page.

This is a GNU bash POSIX regular expression. In Korn Shell, you can use extglob regular expressions to the same effect:
if [[ $num = ?(-)+([0-9]) ]]; then
…
See the section “File name patterns” in the manpage for details.

I had to use ksh expression as shown below to get this to work.
case $num in
+([0-9])*(.)*([0-9]) )
# Variable positive integer
echo "positive integer"
;;
*)
# Not a positive integer
echo "NOPE"
exit
;;
esac

shell script in android gives [: not found

I have this script which works on my linux machine
#!/bin/sh
c=1
if [ $c == 1 ]
then
echo c is 1
else
echo c is 0
fi
But when I use this in android as follows:
#!/system/bin/sh
c=1
if [ $c == 1 ]
then
echo c is 1
else
echo c is 0
fi
It gives an error like:
[: not found
EDIT
Is there any other logic to check the value of $c, whether it is 1 or 0 ?
Android shell have problem with [] in if so is there any other way to check the value of c ?

andriod shell sh is actually a link to busybox, and it is invoked as
busybox sh
you need setup [ applets manually
busybox ln -s /your_original_sh_path/busybox [
if you don't know where busybox is put, try list the /system/bin/sh which you give
ls /system/bin/sh
busybox which busybox

generally [ is an alias for test,
in Linux machine test is at
/usr/bin/test
and
if [ $c == 1 ]
is evaluated as
if test "$c" = 1
BUT here in android there is no test
so if with [] will not work in any case...
i will cross compile test for android and check it....!!!

Android does not provide a full UNIX environment, it is not a UNIX operating system. It has some similarities, much like how Windows also has some similarities to UNIX. Some Android devices and ROMs try to provide more of a UNIX-like environment that others, but you cannot rely on most of the standard shell scripting tools being installed if you are thinking about cross-device compatibility.
So for example, if you look at your GNU/Linux system, you can see that test and [ are actually programs. Try this: ls -l /usr/bin/[. Most Android installs do not include test or [. That means that if you want to try to do actual programming with Android's minimal shell environment, you have to use lots of odd tricks. You can install busybox to get a full UNIX shell environment, or you can even build busybox into your app. I do that when I need to include shell scripts in an app (for example, Lil' Debi and Commotion MeshTether).
Here's an example of writing a killall in Android's /system/bin/sh environment: http://en.androidwiki.com/wiki/Android_Shell_tips_and_tricks You can also use the various parameter expansions to create some logic, you can see an example of that in the Barnacle Wifi Tether scripts.

Use bash:
#!/system/bin/bash
or
#!/system/xbin/bash
You can check where your sh binary is pointing to on your Linux machine:
ls -l /bin/sh
Edit
BTW, use:
c=1
if [ $c -eq 1 ]
then
echo c is 1
else
echo c is 0
fi

Think you using the wrong arithmetic operator and there is a syntax error of a missing ";": try
[ $c -eq 1 ];
Also your location for Bash (sh) might be wrong at the top of your file:
#!/system/bin/sh

How about checking that the .sh file doesn't contain a carriage return before line feed.
Windows \r\n -> CR LF
Unix \n -> LF

use /system/bin/cmp for equality test.
if you need numerically test, substitute $(($c == 1)) with $c
#!/system/bin/sh
echo $c >/tmp/a
echo 1 >/tmp/b
if cmp /tmp/a /tmp/b
echo c is 1
else
echo c is 0
fi

I run into this issue also and found a solution (on another site)
if [[ $b -gt 0]]
then
echo 'Hooray it works'
else
echo 'still works'
fi

Typing on an Android Device straight from computer?

Can you use ADB to type directly on an android device from a computer? If so, how?

Although this question is rather old, I'd like to add this answer:
You may use adb shell input keyevent KEYCODE resp. adb shell input text "mytext". A list of all keycodes can be found here

As Manuel said, you can use adb shell input text, but you need to replace spaces with %s, as well as handle quotes. Here's a simple bash script to make that very easy:
#!/bin/bash
text=$(printf '%s%%s' ${#}) # concatenate and replace spaces with %s
text=${text%%%s} # remove the trailing %s
text=${text//\'/\\\'} # escape single quotes
text=${text//\"/\\\"} # escape double quotes
# echo "[$text]" # debugging
adb shell input text "$text"
Save as, say, atext and make executable. Then you can invoke the script without quotes...
atext Hello world!
...unless you need to send quotes, in which case you do need to put them between the other type of quotes (this is a shell limitation):
atext "I'd" like it '"shaken, not stirred"'

To avoid expansion/evaluation of the text parameter (i.e. for special characters like '$' or ';'), you could wrap them into quotes like this:
adb shell "input text 'insert your text here'"

input does not support UTF-8 or other encodings, you will see something like this if you try it
$ adb shell input text ö
Killed
therefore if these are your intention you need something more robust.
The following script uses AndroidViewClient/culebra with CulebraTester2-public backend to avoid input limitations.
#! /usr/bin/env python3
# -*- coding: utf-8 -*-
from com.dtmilano.android.viewclient import ViewClient
vc = ViewClient(*ViewClient.connectToDeviceOrExit(), useuiautomatorhelper=True)
oid = vc.uiAutomatorHelper.ui_device.find_object(clazz='android.widget.EditText').oid
vc.uiAutomatorHelper.ui_object2.set_text(oid, '你好世界 😄')
it finds an EditText and then enters some Chinese characters and a emoji.
You can achieve the same using bash and curl if entering text is the only you need.
#! /bin/bash
#
# simple-input-text
# - Finds an EditText
# - Enters text
#
# prerequisites:
# - adb finds and lists the device
# - ./culebratester2 start-server
# - jq installed (https://stedolan.github.io/jq/)
#
set -e
set +x
base_url=http://localhost:9987/v2/
do_curl() {
curl -sf -H "accept: application/json" -H "Content-Type: application/json" "$#"
}
oid=$(do_curl -X POST "${base_url}/uiDevice/findObject" \
-d "{'clazz': 'android.widget.EditText'}" | jq .oid)
do_curl -X POST "${base_url}/uiObject2/${oid}/setText" \
-d "{'text': '你好世界 😄'}"

Here is a Bash-based solution that works for arbitrary/complex strings (e.g. random passwords). The other solutions presented here all failed for me in that regard:
#!/usr/bin/env bash
read -r -p "Enter string: " string # prompt user to input string
string="${string// /%s}" # replace spaces in string with '%s'
printf -v string "%q" "${string}" # quote string in a way that allows it to be reused as shell input
adb shell input text "${string}" # input string on device via adb
The following code may be used for repeated/continuous input:
#!/usr/bin/env bash
echo
echo "Hit CTRL+D or CTRL+C to exit."
echo
while true; do
read -r -p "Enter string: " string || { echo "^D"; break; }
string="${string// /%s}"
printf -v string "%q" "${string}"
echo "Sending string via adb..."
adb shell input text "${string}"
done

You can see how it's done in talkmyphone.
They are using Jabber, but it might be useful for you.

When using zsh, here is a more robust function to feed text to Android:
function adbtext() {
while read -r line; do
adb shell input text ${(q)${line// /%s}}
done
}
While Zsh quoting may be slightly different from a regular POSIX shell, I didn't find anything it wouldn't work on. Dan's answer is missing for example > which also needs to be escaped.
I am using it with pass show ... | adbtext.