I have sample data file (csv) as below and required to generate large data from sample file. for that i need to change date (DD) in timestamp and run for loop to generate more data.

14/03/2017 00:05:58,General2,General3,General4,General5,General6,General7

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  • 2
    What do you want to change the date to? A pistachio? – DopeGhoti Aug 16 '17 at 16:48
  • 1
    required to generate monthly data. Hence required to change date with another DD. like 15 – Rakesh C Aug 16 '17 at 16:49

Here is one of the possibilities in bash (tried on Ubuntu 16.04.3 LTS)

Put your csv in a file called yourfile.csv (or change this code), then run this:

for i in `seq 1 30`; do
        NEWDATE=`date -d"${DATE}+${i}day" +'%d/%m/%Y'`
        while read line; do
                echo $line | sed -u -r "s#^.{10}#${NEWDATE}#"
        done <yourfile.csv

It will generate +30 days for EACH input line, so you only need to have file with 1 line. Oh and it accepts date as parameter and will generate +30 days of data starting from that date.

Update for slowness: Try this, maybe it works faster for you:

let i=0
while read line; do
        let i=(i++ % 30)
        NEWDATE=`date -d"${DATE}+${i}day" +'%d/%m/%Y'`
        echo $line | sed -u -r "s#^.{10}#${NEWDATE}#"
done <yourfile.csv

It will be 1M row will make 1M rows, not 1M makes 30M.

  • Your bash script is working perfectly fine. but its taking too much time. Could you please help me with perl or python script. – Rakesh C Aug 17 '17 at 12:29
  • How many lines did you have in your csv file? It works practically instantly for me, and I had just 4 lines. Remember, it makes 30 lines of csv for each 1 line in the file, so if you kept a large csv, it would create a huge one. – Gnudiff Aug 17 '17 at 13:12
  • 1M row we have in sample CSV file – Rakesh C Aug 17 '17 at 14:08
  • Well then use just the first 10 lines of it maybe? – Gnudiff Aug 17 '17 at 15:22
  • Added another solution, which does not generate new lines, but changes all lines in existing file. – Gnudiff Aug 18 '17 at 7:32

To simply change the days in the date to some fixed value like 15, you can do

sed 's/[0-9]*/15/' your.csv

If you want to change it in that file, add the -i option if your sed supports it.

If you want to automate this for all days in many month, better use another tool like python or perl.

Update: Or have some sed fun:

sed -n 'p;x;s/^/0123456789_/;H;g
  P;\#^01/08#!ba' sample.csv

This multiplies each line with each day starting from the given 14/03 to the 01/08. Sorry for drinking too much.

  • Could you please share the example please – Rakesh C Aug 16 '17 at 16:58
  • Share what example? For the automatization? Then you need to define what you need exactly. – Philippos Aug 16 '17 at 17:01
  • yes, for automation – Rakesh C Aug 16 '17 at 17:01
  • 15/03/2017 00:05:58,General2,General3,General4,General5,General6,General7 Just required to change DD rest values will be same. – Rakesh C Aug 16 '17 at 17:02
  • Only for a couple of days or for each day from March 14th to August 1st or what? Please edit the question to clarify. – Philippos Aug 16 '17 at 17:05

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