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Switching user inside a shell script doesn't seem to work

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# 1  
Old 03-24-2014
Switching user inside a shell script doesn't seem to work
Linux version : Oracle Linux 6.4
Shell : Bash

The following script will be run as root. During the execution, it should switch to oracle user and execute few commands.
After googling and searching within unix.com , I came up with the following syntax

## Enclosing all commands in double quotes with the following syntax
Code:
su -l anotheruser -c "command1;command2;command3;..."

## Using single quote like below didn't work for me
Code:
su -l anotheruser -c 'command1;command2;command3;...'

So, I created the following simple script called test.sh and executed it.
But it seems that the switch user using su didn't work properly.
/tmp/who.txt file shows root. It should show orace user if su worked properly.
/tmp/MYVAR2.txt is empty . It should show Duffy
/tmp/Instancename.txt is empty. It should show JUMBO1


Code:
# cat test.sh
#!/bin/bash
#Usage     :  /root/SCRIPTS/test.sh <Argument1>
echo -e "\n"

## Currently you are root user

## su to oracle user and run the following commands which are separated by semi colon

su -l oracle -c "export ORACLE_SID=$11;export MYVAR1=Stomper;export MYVAR2=Duffy; echo `whoami` >/tmp/who.txt;echo $1 >/tmp/Arg_name.txt;echo $ORACLE_SID >/tmp/Instancename.txt;echo $MYVAR2 >/tmp/MYVAR2.txt"

whoami ## Now you should be back as root
#

-- Executing the script
Code:
#
# test.sh JUMBO


root
#

--- Verifying the content of the files
Code:
# cat /tmp/who.txt
root
# cat /tmp/Arg_name.txt
JUMBO
#
#
# cat /tmp/MYVAR2.txt

# cat /tmp/Instancename.txt

#

# 2  
Old 03-24-2014
The variable and command substitutions in the double-quoted string are performed by the parent shell, while it reads the string, before it invokes su.

Regards,
Alister
# 3  
Old 03-24-2014
Because of the use of double quotes, echo `whoami` gets executed before the su - l takes place. What did not work for you, when you were using single quotes?
This User Gave Thanks to Scrutinizer For This Post:
John K
# 4  
Old 03-24-2014
you can try this

Code:
su -l oracle -c "export ORACLE_SID=$11;export MYVAR1=Stomper;export MYVAR2=Duffy; echo \`whoami\` >/tmp/who.txt;echo $1 >/tmp/Arg_name.txt;echo $ORACLE_SID >/tmp/Instancename.txt;echo $MYVAR2 >/tmp/MYVAR2.txt"

This User Gave Thanks to sumitsks For This Post:
John K
# 5  
Old 03-24-2014
Thanks everyone.

I tried enclosing in single quotes. But it doesn't work properly. Any Idea how I can fix this ?

Code:
# cat test_singleQuote.sh
#!/bin/bash
#Usage     :  /root/SCRIPTS/test_singleQuote.sh <Argument1>
# single quote variant of test.sh

echo -e "\n"

## Currently you are root user

## su to oracle user and run the following commands which are separated by semi colon

su -l oracle -c 'export ORACLE_SID=$11; echo $ORACLE_SID >/tmp/ORACLE_SID_VAR; export MYVAR1=Stomper; \
export MYVAR2=Duffy; echo `whoami` >/tmp/who.txt;echo $1 >/tmp/Arg_name.txt; echo $ORACLE_SID >/tmp/Instancename.txt; echo $MYVAR2 >/tmp/MYVAR2.txt'

whoami ## Now you should be back as root
#
#


--- Executing the script
#
Code:
# test_singleQuote.sh SOFIA


root

-- Verifying the contents of files

# cat /tmp/ORACLE_SID_VAR
1 ---------------------> I am expecting SOFIA1 Smilie
#
# cat /tmp/who.txt
oracle ---------------------> Worked as expected Smilie
#
# cat /tmp/Arg_name.txt
----------------------> null. I was expecting SOFIA Smilie
#
# cat /tmp/MYVAR2.txt
Duffy ---------------------> Worked as expected Smilie
#

Any Idea how I can fix this ?
Last edited by vbe; 03-24-2014 at 06:10 AM..
# 6  
Old 03-24-2014
Try this sample code:
Code:
#!/bin/bash
su -l guest -c "export a=$1;export b=$2;echo \`whoami\`>/tmp/me;echo \$a >/tmp/a;echo \$b>/tmp/b"
echo Now I am
whoami
echo -----------
echo Contentes of file me
cat me
echo -----------
echo Contentes of file a
cat a
echo -----------
echo Contents of file b
cat b

And this is the output I am getting:
Code:
./test.sh 1 2
Now I am
root
-----------
Contentes of file me
guest
-----------
Contentes of file a
1
-----------
Contents of file b
2

This User Gave Thanks to chacko193 For This Post:
John K
# 7  
Old 03-24-2014
Thanks Chacko, everyone
Your script works.
How does this work, when all the echo commands put together after the export commands ?
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