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How to get to previous line of a file?

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# 1  
Old 10-07-2010
Question How to get to previous line of a file?
The situation is following :
  1. I have a file from which I am reading record one by one.
  2. While reading I have to check if any line starts with the value "SE".
  3. If, it finds any value starts with "SE", then I have to check whether its preceding line starts with "NE" or not.
  4. If the preceding line starts with "NE", then I have to extract some data from the "NE" line using cut.
  5. Else, I have to to extract some data from the "SE" line using cut.
Please help me to find a way to resolve this problem.

Thanks in advance
# 2  
Old 10-07-2010
Bug
Try this
Code:
#!/bin/ksh

line=Start
line1=Start

while read line
do
var1=`echo ${line} | cut -c 1-2`
var2=`echo ${line1} | cut -c 1-2`
if [ $var1 = 'SE' ]
then
    if [ $var2 = 'NE' ]
    then
    echo $line1 >>Output.txt
    else
    echo $line >>Output.txt
    fi
fi
line1=$line
done<DemoFile.txt

You can change the code as per your requirement.
# 3  
Old 10-07-2010
bash code:
  1. #!/bin/bash
  2. while read L
  3. do
  4.    S1=${L::2}
  5.    if &#91; $S1 = SE ]
  6.    then
  7.       &#91; $S2 = NE ] && OUT="$L2" || OUT="$L"
  8.       echo "$OUT" | cut whatever_you_want_but_i_don_t_know
  9.    fi
  10.    L2="$L"
  11.    S2=${L::2}
  12.    fi
  13. done   <infile
# 4  
Old 10-07-2010
Quote:
Originally Posted by mady135
The situation is following :
  1. If the preceding line starts with "NE", then I have to extract some data from the "NE" line using cut.
Why using cut ? is this a homework? Please post a data sample and expected output.
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