Using boolean condition and variable declaration

rcroyal88 · 10-08-2018, 01:52 PM

I want to check the multiple process id and then with boolean condition if process are up

var1=$(pgrep -f "/home/huy")
var2=$(pgrep -f "/home/gyu")

if [-n $var1]&&[-n $var2]&&[-n $var3] ;
then

echo "Working"

elif "not working"

fi

Variable decalarition is not working for me ,i am getting error.

NevemTeve · 10-08-2018, 02:17 PM

Please quote the problematic variable-declaration, and the error-message.

scasey · 10-08-2018, 02:44 PM

Please use code tags when posting code or output. It will preserve spaces in the code.

Also, please post the error you are getting. It's hard to help when we don't know what the error is.

A space is required between the [ or ] and the enclosed condition to be tested.

astrogeek · 10-08-2018, 02:51 PM

As mentioned by others, to preserve formatting place your code snippets inside [CODE]...[/CODE] tags. You may type those yourself or click the "#" button in the edit controls.

When asking for help troubleshooting your code it is always helpful to post a minimal working example of code which produces an error or incorrect result, along with the actual error message it produces. Only you are sitting at the keyboard and can interact with it, we can only base advice on what you tell us.

rcroyal88 · 10-08-2018, 02:59 PM

Is there any limit how many boolean operatores can be used ?

Here i have used two times ,Can i use it more times as well in unix ???

BW-userx · 10-08-2018, 03:34 PM

this is not even workable code

Code:

if [-n $var1]&&[-n $var2]&&[-n $var3] ;
then

echo "Working"

elif "not working"

fi

it should be

Code:

if [[ condition ]] && [[ condition ]] && [[ condition ]] ; 
then

echo "yeppers"

else

echo "noppers"
fi

you're thinking is in a two conditional testing,

Code:

if [[ condition ]] ; then
echo "something"
elif [[ condition ]]
echo "something"
else
echo "something"
fi

http://www.tldp.org/LDP/Bash-Beginne...l/chap_07.html

astrogeek · 10-08-2018, 03:40 PM

Quote:

Originally Posted by rcroyal88

Is there any limit how many boolean operatores can be used ?

Here i have used two times ,Can i use it more times as well in unix ???

You can chain as many booleans as necessary to express the desired condition.

It would be helpful to others if you would respond to the questions already asked. LQ members are happy to help you solve problems, but doing so requires two-way communication and respect for the time they volunteer to provide that help.

orbea · 10-11-2018, 09:28 AM

Quote:

Originally Posted by BW-userx

it should be

Code:

if [[ condition ]] && [[ condition ]] && [[ condition ]] ; 
then

echo "yeppers"

else

echo "noppers"
fi

The op never mentioned that bash is being used so its worth pointing out that [[ condition ]] with the double brackets is not portable. Additionally its not required in this context.

BW-userx · 10-11-2018, 09:42 AM

bash is the only one I've ever seen using squared bracket conditionals so it is implied ,and not explicit.

orbea · 10-11-2018, 10:13 AM

I'm not sure what you mean?

Code:

if [ "${foo}" ]; then
  bar
fi

The above is fully portable, shells that it will work in include true bourne shells (i.e. hsh), ash, dash, bash, ksh, loksh, mksh, pdksh, posh, yash and zsh.

BW-userx · 10-11-2018, 10:52 AM

Quote:

Originally Posted by orbea

I'm not sure what you mean?

Code:

if [ "${foo}" ]; then
  bar
fi

The above is fully portable, shells that it will work in include true bourne shells (i.e. hsh), ash, dash, bash, ksh, loksh, mksh, pdksh, posh, yash and zsh.

not arguing about the portability part, just expressing my knowledge of bash and bash and bash.

cheers@!