Add text before last matched occurrence of search word in a file

Question

I need to add a few lines of text before the last occurrence of a word (SearchWord in my example) in multiple files.

• search should be case insensitive.
• the word is present in multiple lines of the file.

Existing Data in a file

SearchWord abc defgh
SEARCHWORD abc1234
sEarchWord abcd
sometext 1
sometext 2

Required Output

SearchWord abc defgh
SEARCHWORD abc1234 
NEWLINE_1_ADDED
NEWLINE_2_ADDED
NEWLINE_3_ADDED
sEarchWord abcd
sometext 1
sometext 2

Answer 1

Use ex, the POSIX file editor

ex is the non-visual form of the vi file editor. It actually predates vi. vi (and Vim) still use ex commands; any time you type a colon and enter a command, that is an ex command (though Vim has many custom extensions).

Since ex opens the whole file for reading, rather than operating in a stream, addressing can work backwards as well as forwards, unlike in Sed or Awk.

For this particular edit, use the following one liner:

printf '%s\n' 'set ignorecase' '$+?searchword?i' 'NEWLINE_1_ADDED' 'NEWLINE_2_ADDED' 'NEWLINE_3_ADDED' . x | ex input.txt

To test the command (print to standard output rather than saving to file), use %p rather than x as the final command:

printf '%s\n' 'set ignorecase' '$+?searchword?i' 'NEWLINE_1_ADDED' 'NEWLINE_2_ADDED' 'NEWLINE_3_ADDED' . %p | ex input.txt 

To handle multiple files:

for f in *.txt; do
    printf '%s\n' 'set ignorecase' '$+?searchword?i' 'NEWLINE_1_ADDED' 'NEWLINE_2_ADDED' 'NEWLINE_3_ADDED' . x | ex "$f"
done

---

Explanation

Running the printf command by itself, you can see the commands which are passed to ex:

set ignorecase
$+?searchword?i
NEWLINE_1_ADDED
NEWLINE_2_ADDED
NEWLINE_3_ADDED
.
x

The set command is self-explanatory.

$+ refers to the line after the last line, and ?...? means to search backward from there. (The + makes it so a file with a matching last line will be handled correctly.) i means to "insert" text before the line found.

The . on a line by itself ends the text to be inserted.

x saves and exits.

Answer 2

Easier if you saved those lines in a text file, e.g. infile then used ed to edit your files in-place:

for f in ./*.txt; do
ed -s "$f" <<\IN
.t.
?[kK][eE][yY][wW][oO][rR][dD]?-1 r infile
$d
w
q
IN
done

If you just wanted to insert some text (not the content of a file), it's similar:

for f in ./*.txt; do
ed -s "$f" <<\IN
.t.
?[kK][eE][yY][wW][oO][rR][dD]?-1 s/$\
some_text\
more_text\
last\\_\&_line
$d
w
q
IN

Replace w with ,p to see what it does without modifying the files.
Note that backslashes, ampersands and delimiters have to be escaped in the RHS of a substitution. The same applies to newlines, except the last one.
How it works ? Well, duplicate the last line, search for your keyword backwards, insert the text or the content of the file before that line, delete the duplicated last line, write, quit.

---

Sure, if you don't need to edit those files in place and just want to print the modified versions, like Zanna does, you don't need arcane text editors with a syntax from another age... You can do it with a single sed invocation - and because Wildcard kindly reminded me that in this family of editors there's a dedicated command to insert text before a match let's use that and some branching:

sed -s '1{h;$!d;b end
}
/keyword/I{H;$!d
}
//{x;p;$!d
}
:end
${x;/keyword/Ii\
some_text_here\
more_text_here\
and_a\\_backslash
}' ./*.txt

This only works with gnu sed though... with other seds you'll have to run a loop (this time without the branch part so as to have a blank line between each file content):

for f in ./*.txt; do
sed -s '/[kK][eE][yY][wW][oO][rR][dD]/{H;$!d
}
//{x;p;$!d
}
${x;/[kK][eE][yY][wW][oO][rR][dD]/i\
some_text_here\
more_text_here\
and_a\\_backslash
}' "$f"
done

As you can see even with insert, one still have to escape backslashes and newlines (except the last one). Other than that, it's simple: it just accumulates lines in the hold buffer and exchanges when encountering a match; on last line it exchanges again and inserts the text before the match, if any.

Answer 3

If you have tac and GNU sed you could use

$ tac file | sed '0,/searchword/I s/.*searchword.*/&\nNEWLINE_3_ADDED\nNEWLINE_2_ADDED\nNEWLINE_1_ADDED/I' | tac
SearchWord abc defgh
SEARCHWORD abc1234
NEWLINE_1_ADDED
NEWLINE_2_ADDED
NEWLINE_3_ADDED
sEarchWord abcd
sometext 1
sometext 2

Explanation

• tac print out the file backwards
• 0,/pattern/ operate on first occurence of pattern only
• I case insensitive search
• s/old/new/ replace old with new
• .*searchword.* match the whole line containing searchword
• & the whole matched pattern in replacement
• \n newline

Maybe more readable:

tac file | sed '0,/searchword/I s/.*searchword.*/&\
NEWLINE_ADDED_3\
NEWLINE_ADDED-2\
NEWLINE_ADDED_1/I' | tac