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# 1  
Old 05-30-2013
Code help
can any body tell me

what is the meaning of the following statements

Code:
 
$0 ~ S {
                V = $0
                getline
                if ( $0 == 199 )
                {
                        getline
                        if ( $0 == 225 )
                        {
                                print V RS 258
                                next
                        }
$0 !~ S {
                print $0
                F = 0
        }


Thanks
Khaled
# 2  
Old 05-30-2013
If you are referring to this post by me, here is the explanation:
Code:
SEQ=45654

awk -v S="$SEQ" '                                       # Set S = $SEQ
        $0 == S {                                       # Check if current record $0 == S
                V = $0                                  # Set V = $0 ( current record )
                getline                                 # Get next record
                if ( $0 == 199 )                        # Check if current record $0 == 199
                {
                        getline                         # Get next record
                        if ( $0 == 225 )                # Check if current record $0 == 225
                        {
                                print V RS "258"        # Print V RS (special awk variable - newline by default) "258"
                                next                    # Skip processing current record
                        }
                        else                            # If current record $0 != 255
                        {
                                print V RS "199" RS $0  # Print V RS "199" RS $0
                                next                    # Skip processing current record
                        }
                }
                else                                    # If current record $0 != 199
                {
                        print V RS $0                   # Print V RS $0
                        next                            # Skip processing current record
                }
        }
        $0 != S {                                       # Check if current record $0 != $0
                print $0                                # Print $0 ( current record )
        }
' file

# 3  
Old 05-30-2013
Dear Yoda
what is the expression if want to check for the previous record of the current record not the next record as getline does ?

Thanks
# 4  
Old 05-30-2013
There is no statement in awk which can help get previous record.

Programmers usually use variables to store the data from current record if that is required for any further operation once awk has read the next record.

The use of variable V in the code that I posted is a good example for this usage.
# 5  
Old 05-30-2013
Thanks Yoda

in this case

I need to use the following code which is easier to access pervious or next record as using
Code:
A[I] , A[i+1] and A[i-1]

as following


Code:
 
./ascii <$1 >"$1"ascii 
SEQ=200
awk -v S="$SEQ" '
        {
                A[++c] = $1
        }
        END {
                for ( i = 1; i <= c; i++ )
                {
                        if ( A[i] == S )
                        {
                                C[A[i]]++
                                V[A[i]] = "the letter is " A[i] 
                        }
                }
                for ( k in V )
                {
                        print C[k] " times"
                        print V[k]
                }
        }
' "$1"ascii>200search


But it wont work for large files as it shows memory allocation errors

any advice ?

Thanks
# 6  
Old 05-30-2013
Yes, this will not work for large files because your code is trying to load all records from your input file to an Indexed Array!

Instead you should follow the approach used in previous code. In that one, current record is stored in a variable, getline statement is called to fetch next record and then further comparison is performed. Thus the code is not memory intensive and will work for large files.
This User Gave Thanks to Yoda For This Post:
khaled79
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