sed to search between two patterns and append text at the end of search result only

user_2074310 0
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Here is my file (test.txt):

start
line1
line2
line3
end

I want to search all the lines between the patterns start and end and then append "<" at the end of the searched lines. The final output should be (need an inline replacement in the same file):

start
line1<
line2<
line3<
end

I also want to do an inline replacement in the same file. Here is what I have done till now.

sed -n '/start/,/end/{/start/!{/end/!p;};}' test.txt

This gives me the below output:

line1
line2
line3

But I don't know how I can do the inline replacement in the same line. I tried this but it does not work.

sed -n -i.bkp '/start/,/end/{/start/!{/end/!p;};}; s/$/</' test.txt
sed
2 Answers

This might work for you (GNU sed):

sed -i '/start/,/end/{//b;s/$/</}' file

Select the range between start and end and if it is neither of the two regexps denoting the range, append < to the end of each line.

user_9674920

You can use

sed -i.bkp '/start/{:a;N;/end/!s/$/</;/end/!ba;}' test.txt

Details:

  • /start/ - matches a line containing start and then executes the subsequent block of commands...
    • :a - sets an a label
    • N - reads the next line appending it to pattern space
    • /end/! - if there is no end in the current pattern space...
    • s/$/</ - replace end of string position with < (adds < at the end of the pattern space)
    • /end/!ba - if there is end stop processing block, else, go to a label.

See the online demo:

#!/bin/bash
s='start
line1
line2
line3
end'
sed '/start/{:a;N;/end/!s/$/</;/end/!ba;}' <<< "$s"

Output:

start
line1<
line2<
line3<
end
user_38329700
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