null value variable

[ozi403]

Hi,

I have variable like this:

MB=`grep "$cli:" /var/adm/scripts/deneme|
grep "level="|grep -v "*"|cut -d"," -f2|grep mb`

If MB is a null value, how can I make MB=0 ?

 

[aigles]

[ -z "$MB" ] && MB=0

Jean Pierre.

 

[aigles]

[ -z "$MB" ] && MB=0

can be replaced by

: ${MB:=0}

Another solution is to use the following substition syntax when using your variable :

${MB:-0}

Parameter Substitution

${parameter}
The value, if any, of the parameter is substituted.
Braces are required only when parameter is followed by
a letter, digit, or underscore that is not to be
interpreted as part of its name. If parameter is * or
@, all positional parameters, starting with $1, are
substituted (separated by spaces). Parameter $0 is set
from argument zero when the shell is invoked.

${parameter:-word}
If parameter is set and is non-null, substitute its
value; otherwise substitute word.

${parameter:=word}
If parameter is not set or is null, set it to word; the
value of the parameter is then substituted. Positional
parameters cannot be assigned to in this way.

${parameter:?word}
If parameter is set and is non-null, substitute its
value; otherwise, print word and exit from the shell.
If word is omitted, the message ``parameter null or not
set'' is printed.

${parameter:+word}
If parameter is set and is non-null, substitute word;
otherwise substitute nothing.


Jean Pierre.

 

[PHV]

Another method in one run:
MB=`awk -F, '/\*/{next}
$0~"'$cli:'" && $0~"level=" && $2~"mb"{mb=(mb?mb"\n"$2:$2}
END{print(mb?mb:0)}
' /var/adm/scripts/deneme`

Hope This Help, PH.
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