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How can I find a word (e.g. "/dn") in a text file and add on the next line another word (e.g. "/period")?

I'd like to execute it using MS DOS.

I mean this "/dn" (after /dn is space) is one word (not a fragment of the text, but the whole word--after /dn can be other word on the same line) which I want to find and then after it on the next new line, not replacing the other lines and other words. I mean create a new line between already existing lines.

For example, if I have this input file:

/dn
/name

I want this output:

/dn
/period
/name

and "/" symbol should be with dn, not without it.

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  • 7
    On the next line? Where on the next line? Should it replace what is currently in the next line? Inserta a new line? Insert the text at the beginning of the next line? Please edit your question, show us a simple example input and the output you want to see from it.
    – terdon
    Jul 26, 2017 at 10:54
  • Please edit your question and show us an example of your input and your desired output.
    – terdon
    Jul 26, 2017 at 12:50
  • and "/" symbol should be with "dn", not without it
    – Lunsy
    Jul 26, 2017 at 12:50
  • Thanks. So, will /dn always be the only word in the line? Can you have more than one /dn on the same line? What if you have /dna, does that count? Can you have spaces before or after the /dn?
    – terdon
    Jul 26, 2017 at 13:16
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    All of these are very important details. Don't say "of course" when your question says that /dn is the "single word on one line". This is why it is important to show us representative examples of your data.
    – terdon
    Jul 26, 2017 at 13:44

2 Answers 2

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1. Using sed append

If you want a completely new line with the word /period after each line containing /dn then use sed append:

sed '\:\dn:a/period' filename

the output for your sample would be:

/dn
/period
/name

1. Notes

  • :\dn: search for \dn
  • a/period append /period to the next line (a new line).

2. Search and append to the end of next line

If you want the /period at the end of the next line then use it like this:

sed ':/dn: { N; s:$:/period: }' filename

Here is a sample input:

/dn
/name

and the output:

/dn
/name /period

2. Notes

First we are searching for lines with /dn, then we add the /period at the end of ($) next line (N;).

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  • The OP is very hard to understand, but I think they want the /period to be printed on the next line.
    – terdon
    Jul 26, 2017 at 10:56
  • Updated the answer ;)
    – Ravexina ♦
    Jul 26, 2017 at 10:59
  • for the noobs, can you show full cmd code. using my expamle
    – Lunsy
    Jul 26, 2017 at 14:16
  • @Lunsy updated the answer.
    – Ravexina ♦
    Jul 26, 2017 at 18:51
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If file.txt contains string /dn then You can run this command:

$ grep -i "\/dn" file.txt | xargs -I{} printf "%s\n/period" {}

It will print

/dn
/period
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  • 4
    i) why are you making this case insensitive? That will also match Dn/, dN/ and DN/. The OP only specified dn/. ii) What's the point of the grep? That will print the entire line matching dn/, not the dn/ alone. More importantly, this will ignore all lines that don't have /dn, so change the OP's input. iii) you don't actually need the -I{} or {}, that's the default behavior of xargs. iv) you might want to add a \n after the /period as well. vi) You also don't need to escape the / for grep: grep /dn file.txt works fine.
    – terdon
    Jul 26, 2017 at 10:57

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