CODEWITHSUNDEEP
bashshellsh
Dennis Vymer
Dennis Vymer

Reputation: 119

bourne shell, editing file, with specific column and row

I am trying to write the current date to a file. I want to write it to the 2nd row 2nd column (columns are seperated by ';')

Using Shell

What I tried so far, Not Working:

paste <(echo "$(date)") <(awk -F ";" '{print $2}' file)

Is there any smart way to do so?

example 'file':

John;Wed Mar 14 19:41:38 CET 2018;18
Sandra;Mon Mar 14 19:41:38 CET 2018;21
David;Sun Mar 14 19:41:38 CET 2018;25

example after editing 'file':

John;Wed Mar 14 19:41:38 CET 2018;18
Sandra;The Date When Editing The File With Script;21
David;Sun Mar 14 19:41:38 CET 2018;25

Upvotes: 1

Views: 66

Answers (2)

John1024
John1024

Reputation: 113924

To replace the second row second column with the current date:

$ awk -F";" -v d="$(date)" 'NR==2{$2=d} 1' OFS=";" file
John;Wed Mar 14 19:41:38 CET 2018;18
Sandra;Wed Mar 14 13:28:59 PDT 2018;21
David;Sun Mar 14 19:41:38 CET 2018;25

How it works

  • -F";"

    This tells awk to use ; as the field separator.

  • -v d="$(date)"

    This defines an awk variable d that contains the current date.

  • NR==2{$2=d}

    On the second row, NR==2, this tells awk to replace the second column, $2, with that value of variable d.

  • 1

    This is awk's shorthand for print-the-current-line.

  • OFS=";"

    This tells awk to use ; as the field separator on output.

Modifying the file in-place

To modify the file in-place using a modern GNU awk:

gawk -i inplace -F";" -v d="$(date)" 'NR==2{$2=d} 1' OFS=";" file

To modify the file using macOS or BSD or older GNU awk:

awk -F";" -v d="$(date)" 'NR==2{$2=d} 1' OFS=";" file >tmp && mv tmp file

Matters of style

The following three lines are all equivalent. Which one you use is a matter of style:

awk -F";" -v d="$(date)" 'NR==2{$2=d} 1' OFS=";" file
awk -F";" -v d="$(date)" -v OFS=";" 'NR==2{$2=d} 1' file
awk -F";" 'NR==2{$2=d} 1'  d="$(date)" OFS=";" file

Upvotes: 3

user 923227
user 923227

Reputation: 2715

Can you try this one:

sed "2s/\(^[^\;]*\;[^\;]*\)/\1\;`date`/" <filename>

Upvotes: 0

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