Insert multiple lines into a file after specified pattern using shell script

Question

I want to insert multiple lines into a file using shell script. Let us consider my input file contents are: input.txt:

abcd
accd
cdef
line
web

Now I have to insert four lines after the line 'cdef' in the input.txt file. After inserting my file should change like this:

abcd
accd
cdef
line1
line2
line3
line4
line
web

The above insertion I should do using the shell script. Can any one help me?

score 123 · Accepted Answer · edited Mar 20 '16 at 14:47

123

Another sed,

sed '/cdef/r add.txt' input.txt

input.txt:

abcd
accd
cdef
line
web

add.txt:

line1
line2
line3
line4

Test:

sat:~# sed '/cdef/r add.txt' input.txt
abcd
accd
cdef
line1
line2
line3
line4
line
web

If you want to apply the changes in input.txt file. Then, use -i with sed.

sed -i '/cdef/r add.txt' input.txt

If you want to use a regex as an expression you have to use the -E tag with sed.

sed -E '/RegexPattern/r add.txt' input.txt

edited Mar 20 '16 at 14:47

yoano

1,466
2
16
20

answered Mar 19 '14 at 05:58

sat

14,589
7
46
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1

Is there a way to do this the other way around (remove text found in add.txt from input.txt) ? – Sina Sep 14 '14 at 00:20
3

A variation, that allows for an anonymous file is to pipe a here document into a sed invocation and use the `r` command to read from `/dev/stdin`. – potong Aug 02 '18 at 14:19
Hi, is there a quick way to add 4 spaces before the added lines from `add.txt` ? – Hud Oct 16 '20 at 12:53
1

The problem with this approach is that if you have 100 occurrences of `cdef` in the file, it will paste `add.txt` contents into your file 100 times as well :( – RAM237 Aug 07 '22 at 14:02

score 52 · Answer 2 · answered Mar 19 '14 at 05:51

52

Using GNU sed:

sed "/cdef/aline1\nline2\nline3\nline4" 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/aline1\nline2\nline3\nline4" input.txt

answered Mar 19 '14 at 05:51

devnull

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I am new to `sed` but wow I am in love with its power! If you want to append an empty newline *first* you have to escape the backslash character after the append command like this : `sed "/cdef/a\\\nline1\nline2\nline3\nline4" input.txt`. I am not sure why it works like that though, if somebody could explain this would be nice! – hdl Sep 23 '15 at 13:20
2

The current command inserts the line* on every mention of `cdef`, is there a way to make it so that it only inserts on the first time it encounters `cdef` and no more? – CMCDragonkai Oct 20 '15 at 13:32
2

MacOS `sed` doesn't implement the `a` command precisely the same as GNU `sed`, so the above won't work in MacOS without mods - at least as of macOS 10.13 ( see https://unix.stackexchange.com/a/131940/230763 ) – Mike Lutz Jul 13 '18 at 22:19
MacOS `sed` also doesn't treat the `-i` option the same as GNU `sed`. On MacOS, `-i` requires an argument with a backup suffix. You would want to specify `-i ''`. – Craig Buchek Feb 20 '23 at 03:48

score 31 · Answer 3 · answered Jul 30 '18 at 00:32

31

sed '/^cdef$/r'<(
    echo "line1"
    echo "line2"
    echo "line3"
    echo "line4"
) -i -- input.txt

answered Jul 30 '18 at 00:32

rindeal

993
11
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Missed this good answer. Shorter but less readable is `sed '/^cdef$/r' <(printf "%s\n" line{1..4}) -i -- input.txt`. – Walter A Jan 02 '19 at 10:40
2

Note that this won't work in containers when you're issuing the command from the host, as the file descriptor from `<(...)` will be created on the host and not the guest. Using the `/someline/a` method works better, especially if you do something like `sed "/someline/a$(echo 'here you can have newlines' | tr \\n @ | sed '\''s/@/\\n/g'\')" -i -- input.txt` (not a full example and not properly tested, I don't have time for it now, but this should include the building blocks for what you need). – Luc Feb 19 '21 at 00:04

score 19 · Answer 4 · answered Mar 19 '14 at 05:58

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

score 8 · Answer 5 · answered Mar 17 '20 at 09:57

Here is a more generic solution based on @rindeal solution which does not work on MacOS/BSD (/r expects a file):

cat << DOC > input.txt
abc
cdef
line
DOC

$ cat << EOF | sed '/^cdef$/ r /dev/stdin' input.txt
line 1
line 2
EOF

# outputs:
abc
cdef
line 1
line 2
line

This can be used to pipe anything into the file at the given position:

$ date | sed '/^cdef$/ r /dev/stdin' input.txt

# outputs
abc
cdef
Tue Mar 17 10:50:15 CET 2020
line

Also, you could add multiple commands which allows deleting the marker line cdef:

$ date | sed '/^cdef$/ {
  r /dev/stdin
  d
}' input.txt

# outputs
abc
Tue Mar 17 10:53:53 CET 2020
line

Walter A · Answer 6 · 2019-01-02T10:21:47.503

1

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 "%s\n" line{1..4}) input.txt

edited Jan 02 '19 at 10:21

answered Dec 31 '18 at 11:41

Walter A

19,067
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score 0 · Answer 7 · answered May 22 '17 at 20:59

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

score 0 · Answer 8 · answered Aug 08 '21 at 21:38

suppose you have a file called 'insert.txt' containing the lines you want to add:

line1
line2
line3
line4

If the PATTERN 'cdef' REPEATS MULTIPLE TIMES in your input.txt file, and you want to add the lines from 'insert.txt' after ALL occurrences of the pattern 'cdef' , then a easy solution is:

sed -i -e '/cdef/r insert.txt' input.txt

but, if the PATTERN 'cdef' REPEATS MULTIPLE TIMES in your input.txt file, and you want to add the lines from 'insert.txt' ONLY AFTER THE FIRST OCCURRENCE of the pattern, a beautiful solution is:

printf "%s\n" "/cdef/r insert.txt" w | ed -s input.txt

Both solution will work fine in case the pattern happens only once in your input.txt file.

score 0 · Answer 9 · answered Mar 11 '22 at 14:47

0

Based on @rindeal solution but with better readability of the input

sed '/^cdef$/r'<(cat <<EOF
line1
line2
line3
line4
EOF
) -i -- input.txt

answered Mar 11 '22 at 14:47

Pavel Tankov

429
1
4
12

score 0 · Answer 10 · answered Apr 10 '22 at 22:37

Putting the content over the 4th line (like you want)

sed -i "4i line1\nline2\nline3\nline4" input.txt

If you don't want to save the changes to the file in-place, remove "-i" :

sed "4i line1\nline2\nline3\nline4" input.txt

Using sed by GNU*

If you started input.txt with:

abcd
accd
cdef
line
web

this would produce:

abcd
accd
cdef
line1
line2
line3
line4
line
web

score -1 · Answer 11 · answered Nov 26 '18 at 15:47

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 xx\n 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}

score -1 · Answer 12 · answered Jan 04 '21 at 09:11

-1

if you want to do that with a bash script, that's useful.

echo $password | echo 'net.ipv4.ping_group_range=0 2147483647' |  sudo -S tee -a /etc/sysctl.conf

answered Jan 04 '21 at 09:11

N'bia

69
7

2

Can you add some explanation to your command to help the future readers understand what has been done? – Ruli Jan 04 '21 at 09:40

Insert multiple lines into a file after specified pattern using shell script

12 Answers12

STEP 1 copy until the pattern

STEP 2 add your lines

STEP 3 add the rest of the file

REPLACE original file

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

Linked

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