CODEWITHSUNDEEP
bashshell
Joao Vitorino
Joao Vitorino

Reputation: 3266

bash script if statement

I made a script to check tnsping but the if statement does not working properly. The following is the script:

ping=$(tnsping oracle1 |grep OK| awk -F" " '{print $1 }')

if [ -n $ping ]
then
   echo "OK"
else
   echo "NOT OK"
fi

If a execute change oracle for a non-existing oracle server I also receive "OK".

-n = The length of STRING is greater than zero

Upvotes: 0

Views: 419

Answers (2)

agc
agc

Reputation: 8446

Neither the $ping variable nor awk are necessary, since grep can return an exit code to if:

if tnsping oracle1 | grep --quiet OK
then
   echo "OK"
else
   echo "NOT OK"
fi

Upvotes: 2

Andreas Louv
Andreas Louv

Reputation: 47137

Wrap double quotes around $ping:

if [ -n "$ping" ]
then
   echo "OK"
else
   echo "NOT OK"
fi

Or it will undergo word splitting and globbing and resolve in the following arguments for [: '-n' and ']' when $ping is empty. which is the same as:

 if [ '-n' '-n' ']'

See man test:

-n STRING
the length of STRING is nonzero
STRING
equivalent to -n STRING
-z STRING
the length of STRING is zero

And FYI you can omit the call to grep and use awk directly. And since the default Field Separator (-F) is space that can be omitted as well:

ping=$(tnsping oracle1 | awk '/OK/{print $1 }')

Upvotes: 4

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