Replace multiple lines of file in Shell with variable

Question

I have a txt file with:

A
B
<anything>
C
D

I want to replace from B to C in the file with a string, but this is not matching:

sed -i -e "s/B.*C/replace/g" $fileName

I have found how to target the multi-line string with:

awk '/B/,/C/' $fileName

John1024 · Accepted Answer · 2014-10-10 23:54:00Z

2

$ awk '/B/{print "Replacement Text"} /B/,/C/{next} 1' "$fileName" 
A
Replacement Text
D

Explanation of awk code:

/B/{print "Replacement Text"}

When we see the B line, print out the new text, whatever it is.
/B/,/C/{next}

Any any line between B and C inclusive, skip the rest of the commands and jump to the next line.
1

This is awk shorthand for print the current line.

If the replacement text is in the shell variable newtext, then use:

awk -v new="$newtext" '/B/{print new} /B/,/C/{next} 1'

If you have GNU awk v4.1.0 or better:

$ awk -i inplace '/B/{print "Replacement Text"} /B/,/C/{next} 1' "$fileName"

With earlier versions:

awk '/B/{print "Replacement Text"} /B/,/C/{next} 1' "$filename" >tmp && mv tmp "$filename"

answered Oct 10, 2014 at 23:12

John1024

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3 Comments

I'm trying to modify the text file not just print

what if replacement text is a variable?

@user2827214 Assuming the replacement text is in a shell variable, see updated answer. If not, let me know the source of the replacement text.

potong · Accepted Answer · 2014-10-11 15:54:26Z

0

This might work for you (GNU sed):

sed '/B/,/C/c\replacement' file

or:

var=replacement; sed '/B/,/C/c\'$var file

answered Oct 11, 2014 at 15:54

potong

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