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I need to add a the multi line string in TEXT into myfile.txt where it last find the text # My Search.

If it was a regular pattern replace then sed with i would do the trick. However I don't know how to go 2 lines above the match in sed.

Example, myfile.txt:

text1

text2

#

# My Search

#

text4

text5

#

# My Search

#

text6

TEXT looks like:

TEXT="

[my search]

home=/var/home

string=random



"

myfile.txt should look at the end:

text1

text2

#

# My Search

#

text4

text5



[my search]

home=/var/home

string=random



#

# My Search

#

text6

Use grep -n to extract the line number, then use it in a sed address to insert the text, which needs to be properly quoted, i.e. there must be a backslash before each newline:

line=$(grep -n '# My Search' myfile.txt | tail -n1 | cut -f1 -d:)

((--line))

text=${TEXT//$'n'/$'\n'}

text=${text%$'\n'}$'n'



sed "$line i \

$text" myfile.txt

tac + bash (variable substitution) + GNU sed approach:

txt_reversed=$(echo "$TEXT" | tac)

tac myfile.txt 

| sed -e "N;N;N; s~#n# My Searchn#~&${txt_reversed//$'n'/\n}n~" | tac

The output:

text1

text2

#

# My Search

#

text4

text5



[my search]

home=/var/home

string=random



#

# My Search

#

text6

The easiest way to do this in one go is to use a tool that can search backward, ed is one of them. Ideally you would have the text saved in a file (e.g. insert.txt) and insert the file content two lines before the last occurrence of PATTERN so you could run:

ed -s infile <<IN

.t.

?PATTERN?-2r insert.txt

$d

,p

q

IN

It finds the last occurrence of PATTERN, goes up another 2 lines and reads in insert.txt. It then prints the content of the buffer via ,p. Replace that with w if you want to edit the file in-place.

With other tools that can't search backward a two-pass is the way to go: 1st pass - get the line number and 2nd pass - insert the text content after line NR-2 or before line NR-1. For text saved in a variable I favor awk over other tools that rely on regex (the latter require pre-processing the text to be inserted so as to escape any special characters: there are several ones that need escaping, not just the newline, depending on the technique used):

export TEXT

awk 'NR==FNR{if ($0 ~ /PATTERN/){c=NR};next}

{if (FNR==(c-1)){print ENVIRON["TEXT"]}};1' infile infile