compare strings in shell scripting

culin · 09-26-2007, 02:19 AM

Hi all.....

Code:

#!/bin/sh
echo "Please wait.... The installation is in progress........ "
echo "Searching for the previous installations of scratchbox....."

j="installed"

i= apt-cache show scratchbox-core | grep "Status" | awk '{print $4}'

if [ "$j" == "$i" ]

then
        echo "Scratchbox is already installed on this system"
else
        echo "Scratchbox is not installed in the system......"
        echo "Installing scratchbox.. please wait....."
fi

can anyone tell me what is wrong in the above script...
it is always echoing "Scratchbox is not installed in the system......"
eventhough the output of the command
apt-cache show scratchbox-core | grep "Status" | awk '{print $4}'
is "installed"

colucix · 09-26-2007, 02:29 AM

Code:

i= apt-cache show scratchbox-core | grep "Status" | awk '{print $4}'

Here you should get a command not found error, since the syntax of the assigment is wrong. The correct syntax for command substitution is

Code:

i=$(apt-cache show scratchbox-core | grep Status | awk '{print $4}')

culin · 09-26-2007, 03:25 AM

oh..wow.. thanks a lot colucix...

and can u please tell me what is the difference between the first one (the one i did ) and the second one (one suggested by u) ???
i am a newbie to scripting...
i will post back if i have some problems in scripting..
thanks again...

culin · 09-26-2007, 04:54 AM

again another problem.. why this logical or inside the shell script is not working... ??? !!!
if [("$j" != "$cpu") -o ("$j" != "$libs")]

it is telling syntax error near unexpected token `"$j"'

matthewg42 · 09-26-2007, 05:20 AM

Try:

Code:

if [ "$J" != "$cpu" ] || [ "$J" != "$libs" ]; then
   ...
fi

matthewg42 · 09-26-2007, 05:21 AM

Or:

Code:

case "$J" in
$cpu|$libs)
   ...
   ;;
esac

culin · 09-26-2007, 05:32 AM

hey...matthewg42 thanks a lot ...

i am really confused here....
why scripting is like this.. just because of spacing it gives me different output and error... ??? !!!! really confused.. is there a standard way of formatting these expressions.. where can i get all these info... ?
and i tried even without the semicolon( at the end of the if statement.. it is working without semicolon also... why is like this ??

matthewg42 · 09-26-2007, 06:03 AM

Shell scripting syntax is a little bit clunky compared to other languages, partly because the parser is a single-pass affair, rather than multi-pass parsers used in other languages. But like anything, only you've learned it, it has it's moments.

Perhaps you'd do better to start with a tutorial rather than expecting to be able to implement your script without learning the basics.

culin · 09-27-2007, 12:04 AM

ya sure matthewg42... thanks...

charithsrng · 01-24-2013, 12:44 AM

Quote:

Originally Posted by culin

Hi all.....

Code:

#!/bin/sh
echo "Please wait.... The installation is in progress........ "
echo "Searching for the previous installations of scratchbox....."

j="installed"

i= apt-cache show scratchbox-core | grep "Status" | awk '{print $4}'

if [ "$j" == "$i" ]

then
        echo "Scratchbox is already installed on this system"
else
        echo "Scratchbox is not installed in the system......"
        echo "Installing scratchbox.. please wait....."
fi

can anyone tell me what is wrong in the above script...
it is always echoing "Scratchbox is not installed in the system......"
eventhough the output of the command
apt-cache show scratchbox-core | grep "Status" | awk '{print $4}'
is "installed"

make the changes as below

i=`apt-cache show scratchbox-core | grep "Status" | awk '{print $4}'`

chrism01 · 01-24-2013, 01:33 AM

The original conversation is from 2007(!); please don't bring up old posts like that.