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comparing variables in an if statement


 
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# 1  
Old 03-03-2012
comparing variables in an if statement

Code:
#!/bin/bash
#timetest
TIMENOW="$(date)"
T1=12:00:00
echo $TIMENOW >timenow
cat timenow |cut -f4 -d' ' >time1
T2=$(sed -n "${1}p" time1)
echo "T1 = " $T1
echo "T2 = " $T2
if[ $T1 -gt $T2 ] then
  echo $T1 
 else
  echo $T2 
fi

I thought scripting was simple! So why does this script result in:
Code:
T1 =  12:00:00
T2 =  16:04:43
/home/admin/user/bin/timetest: line 10: if[ 12:00:00 -gt 16:04:43 ]: command not found
12:00:00
/home/admin/user/bin/timetest: line 12: syntax error near unexpected token `else'
/home/admin/user/bin/timetest: line 12: ` else'


Last edited by Scott; 03-04-2012 at 04:13 PM.. Reason: Please use code tags
# 2  
Old 03-03-2012
You are getting the command not found message because you need a space between the 'if' and the open bracket:

Code:
if [ $T1 -gt $T2 ] then

You will also likely receive an error once you fix that as '-gt' implies integer comparison, and your variables contain non-numeric chaaracters (colons). You might consider something like this:

Code:
t1="12000000"
t2="$(date "+%H%M%S")"
if [ $t1 -gt $t2 ]
then
    echo true
else
    echo false
fi

Both timestamps are created without colons and can be compared as integers.
# 3  
Old 03-04-2012
Thank you for the replies. The placement of 'then' was important as was the space after 'if' ........Thank you, Agama! However I still needed further modification. Here is the script that works:
Code:
#!/bin/bash
#timetest
TIMENOW="$(date)"
T1=12:00:00
echo $TIMENOW >timenow
cat timenow |cut -f4 -d' ' >time1
T2=$(sed -n "${1}p" time1)
echo "T1 = " $T1
echo "T2 = " $T2
if [[ $T1 < $T2 ]] #or [ $T1 \< $T2 ] for comparing ascii strings
 then
  echo $T1 
 else
  echo $T2 
fi


Last edited by Scott; 03-04-2012 at 04:13 PM.. Reason: Code tags
# 4  
Old 03-04-2012
Good. I still think you are going through more work than needed to get T2. All that effort of cutting, echoing and tmp files isn't needed:

Code:
T2=$( date "+%H%M%S" )    # without colons
T2=$( date "+%X" )              # hr:min:sec

# 5  
Old 03-04-2012
Thank you! I was concentrating so hard on the 'if' I neglected the more obvious......Thanks again.

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