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check for null

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# 1  
Old 07-21-2010
Data check for null
hi,

i have 3 lines of output , if second line exists then only condition within the if loop has to exeute other wise it has exit from loop.
i had tried like this but not getting

please help me ...

Code:
Code:
if [ condition]; then 
 
    echo "success"
else
 echo ""

Moderator's Comments:
Mod Comment Use code tags please, ty.
Last edited by zaxxon; 07-21-2010 at 09:43 AM..
# 2  
Old 07-21-2010
Is there a string/pattern you expect in the 2nd line or is it just a check on how many lines you have overall?
# 3  
Old 07-22-2010
Question check for empty line
hi,

i have input like this,
i have to check that second line exists or not ? Smilie
which condition i have use??? please help me

INPUT:
Code:
Machine ID     Machine Name   Master    Check Error Files   MachineComments
-----------------------------------------------------------------------
1                     SSZ0797             Y              Y                      ssz0797
2                                      SSZ0795             N              Y                      SLAVE_1
3                                      SSZ0796             N              Y                      SLAVE_2

Moderator's Comments:
Mod Comment Use code tags.
Last edited by zaxxon; 07-22-2010 at 03:14 AM.. Reason: to format
# 4  
Old 07-22-2010
when you tell you are checking for the second line, is it that you are checking for the existance of
Code:
2 SSZ0795 N Y SLAVE_1

, or any specific row..??? Machine ID, Machine Name etc....

please be a little detailed...
# 5  
Old 07-22-2010
check for null
i am checking for second line existence,

if second line exists some code has to execute otherwise it has to exit from the loop
# 6  
Old 07-22-2010
Code:
# cat check
1 SSZ0797 Y Y ssz0797
2 SSZ0795 N Y SLAVE_1
3 SSZ0796 N Y SLAVE_2

Code:
if [[ `grep -w "2 [[:alnum:]][[:alnum:]]*" check` ]] ; then echo "2 line is exist"; else echo "2 line is not exist"; fi
2 line is exist


Code:
# cat check
1 SSZ0797 Y Y ssz0797
2
3 SSZ0796 N Y SLAVE_2

Code:
# if [[ `grep -w "2 [[:alnum:]][[:alnum:]]*" check` ]] ; then echo "2 line is exist"; else echo "2 line is not exist"; fi
2 line is not exist

# 7  
Old 07-22-2010
its not working Smilie
i am taking the input from one file and trying to check the second line existence

Code:
SWADM=$SWDIR/util/swadm

SERVEREXISTS=`$SWADM show_servers | awk '{print $1}'| head -5 | tail -1`

if [ "$SERVEREXISTS" != "" ]; then 
echo "line exists"

else
echo "line does not exits"
fi

please help me...
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