Using GNU sed:

sed "/cdef/aline1nline2nline3nline4" input.txt

If you started with:

abcd

accd

cdef

line

web

this would produce:

abcd

accd

cdef

line1

line2

line3

line4

line

web

If you want to save the changes to the file in-place, say:

sed -i "/cdef/aline1nline2nline3nline4" input.txt

Using awk:

awk '/cdef/{print $0 RS "line1" RS "line2" RS "line3" RS "line4";next}1' input.txt 

Explanation:

• You find the line you want to insert from using /.../
  


• You print the current line using print $0
  


• 
  RS is built-in awk variable that is by default set to new-line.


• You add new lines separated by this variable


• 
  1 at the end results in printing of every other lines. Using next before it allows us to prevent the current line since you have already printed it using print $0.

$ awk '/cdef/{print $0 RS "line1" RS "line2" RS "line3" RS "line4";next}1' input.txt

abcd

accd

cdef

line1

line2

line3

line4

line

web

To make changes to the file you can do:

awk '...' input.txt > tmp && mv tmp input.txt

sed '/^cdef$/r'<(

    echo "line1"

    echo "line2"

    echo "line3"

    echo "line4"

) -i -- input.txt

This answer is easy to understand

• Copy before the pattern


• Add your lines


• Copy after the pattern


• 
  

  Replace original file

  
  
  

  FILENAME='app/Providers/AuthServiceProvider.php'

  
  

STEP 1 copy until the pattern

sed '/THEPATTERNYOUARELOOKINGFOR/Q' $FILENAME >>${FILENAME}_temp

STEP 2 add your lines

cat << 'EOL' >> ${FILENAME}_temp



HERE YOU COPY AND

PASTE MULTIPLE

LINES, ALSO YOU CAN

//WRITE COMMENTS



AND NEW LINES

AND SPECIAL CHARS LIKE $THISONE



EOL

STEP 3 add the rest of the file

grep -A 9999 'THEPATTERNYOUARELOOKINGFOR' $FILENAME >>${FILENAME}_temp

REPLACE original file

mv ${FILENAME}_temp $FILENAME

if you need variables, in step 2 replace 'EOL' with EOL

cat << EOL >> ${FILENAME}_temp



this variable will expand: $variable1



EOL

I needed to template a few files with minimal tooling and for me the issue with above sed -e '/../r file.txt is that it only appends the file after it prints out the rest of the match, it doesn't replace it.

This doesn't do it (all matches are replaced and pattern matching continues from same point)

#!/bin/bash



TEMPDIR=$(mktemp -d "${TMPDIR:-/tmp/}$(basename $0).XXXXXXXXXXXX")

# remove on exit

trap "rm -rf $TEMPDIR" EXIT



DCTEMPLATE=$TEMPDIR/dctemplate.txt

DCTEMPFILE=$TEMPDIR/dctempfile.txt



# template that will replace

printf "0replacement

1${SHELL} data

2anotherlinenoEOL" > $DCTEMPLATE



# test data

echo -e "xxy n987 nxx xxn yz yxxyy" > $DCTEMPFILE



# print original for debug

echo "---8<--- $DCTEMPFILE"

cat $DCTEMPFILE

echo "---8<--- $DCTEMPLATE"

cat $DCTEMPLATE

echo "---8<---"



# replace 'xx' -> contents of $DCTEMPFILE

perl -e "our $fname = '${DCTEMPLATE}';" -pe 's/xx/`cat $fname`/eg' ${DCTEMPFILE}

You can use awk for inserting output of some command in the middle of input.txt.

The lines to be inserted can be the output of a cat otherfile, ls -l or 4 lines with a number generated by printf.

awk 'NR==FNR {a[NR]=$0;next}

    {print}

    /cdef/ {for (i=1; i <= length(a); i++) { print a[i] }}'

    <(printf "%sn" line{1..4}) input.txt