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Read a file using awk for a given no of lines.

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# 1  
Old 08-27-2012
Read a file using awk for a given no of lines.
Hi,

how do i read a file using awk for a given no of line?

e.g
1. read only first 50 line.
2. read starting from line 20 to line 60..

thanks in advance.

-alva
# 2  
Old 08-27-2012
Small two line shell script that takes two optional parameters: number of lines to print ($1) and the starting line number ($2) Reads from stdin.

Code:
#!/usr/bin/env ksh
awk -v startl=${2:-1} -v nlines=${1:-10} ' NR - (startl-1) > nlines { exit( 0 ); } NR >= startl '

Lots of ways to modify this to suit your needs.

EDIT: should mention, if it's not obvious, the default starting line is 1, and default number of lines to print is 10.
This User Gave Thanks to agama For This Post:
alvagenesis
# 3  
Old 08-28-2012
Hi Agama,

thank you for your prompt response.

-alva.


i have a followup question, how to incorporate a filter(using unix timestamp) in that script?

eg.

input file structure : timestamp , data1, data2, data3.....

1.read only lines starting from todate to 10 days later. (aug 19-28)

-alva
# 4  
Old 08-28-2012
Depends on the version of awk. What is output when you run: awk --version and what operating system are you using?
# 5  
Old 08-28-2012
Code:
GNU Awk 3.1.5

RHEL5
# 6  
Old 08-28-2012
Assuming that version of gawk has mktime()....

Forgot to ask, and you didn't specify the format of the timestamp. Assuming it is in the first two tokens of each input line, and is of the format yyyy-mm-dd hh:mm:ss then try this:

Code:
awk -v startt="${1:-2012-8-20  00:00:00}" -v ndays=${2:-10} '
    BEGIN {
        gsub( "[-:]", " ", startt );
        sts = mktime( startt );
        ets = sts + (ndays * 86400 );
    }

    # assuming timestamp is yyyy-mm-dd hh:mm:ss in the first two columns
    {
        ctd = $1;    # ensure that the original input isnt changed -- save and strip undesired characters
        ctt = $2;
        gsub( "[-:]", " ", ctd );
        gsub( "[-:]", " ", ctt );

        cts = mktime( ctd " " ctt );
        if( cts >= sts )
        {
            if( cts <= ets )
                print;
            else
                exit( 0 );
        }
    }
' input-file

EDIT: If embedded into a script, you can invoke with starting date string, and number of days to print:

Code:
print_from_log  "2012-08-10 00:00:00" 10

This User Gave Thanks to agama For This Post:
alvagenesis
# 7  
Old 08-28-2012
hi agama,

sorry for the confusion. what i meant by time stamp was the unix Epoch.

here is the sample data in the input file.

Code:
1344324384:LOTSTART        0000JPHMES9624-NEW LOTS CREATED-SOURCE LOT 3A MD03AUG16
1344324385:LOTSTART        0000JPHMES9624-NEW LOTS CREATED-SOURCE LOT 3A MD03AUG31 
1344324386:LOTSTART        0000JPHMES9624-NEW LOTS CREATED-SOURCE LOT 3A 1C800017
....
...
..
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