Insert a line at specific line number with sed or awk
SedAwkSed Problem Overview
I have a script file which I need to modify with another script to insert a text at the 8th line.
String to insert: Project_Name=sowstest, into a file called start.
I tried to use awk and sed, but my command is getting garbled.
Sed Solutions
Solution 1 - Sed
sed -i '8i This is Line 8' FILE
inserts at line 8
This is Line 8
into file FILE
-i does the modification directly to file FILE, no output to stdout, as mentioned in the comments by glenn jackman.
Solution 2 - Sed
An ed answer
ed file << END
8i
Project_Name=sowstest
.
w
q
END
. on its own line ends input mode; w writes; q quits. GNU ed has a wq command to save and quit, but old ed's don't.
Further reading: https://gnu.org/software/ed/manual/ed_manual.html
Solution 3 - Sed
OS X / macOS / FreeBSD sed
The -i flag works differently on macOS sed than in GNU sed.
Here's the way to use it on macOS / OS X:
sed -i '' '8i\
8 This is Line 8' FILE
See man 1 sed for more info.
Solution 4 - Sed
the awk answer
awk -v n=8 -v s="Project_Name=sowstest" 'NR == n {print s} {print}' file > file.new
Solution 5 - Sed
POSIX sed (and for example OS X's sed, the sed below) require i to be followed by a backslash and a newline. Also at least OS X's sed does not include a newline after the inserted text:
$ seq 3|gsed '2i1.5'
1
1.5
2
3
$ seq 3|sed '2i1.5'
sed: 1: "2i1.5": command i expects \ followed by text
$ seq 3|sed $'2i\\\n1.5'
1
1.52
3
$ seq 3|sed $'2i\\\n1.5\n'
1
1.5
2
3
To replace a line, you can use the c (change) or s (substitute) commands with a numeric address:
$ seq 3|sed $'2c\\\n1.5\n'
1
1.5
3
$ seq 3|gsed '2c1.5'
1
1.5
3
$ seq 3|sed '2s/.*/1.5/'
1
1.5
3
Alternatives using awk:
$ seq 3|awk 'NR==2{print 1.5}1'
1
1.5
2
3
$ seq 3|awk '{print NR==2?1.5:$0}'
1
1.5
3
awk interprets backslashes in variables passed with -v but not in variables passed using ENVIRON:
$ seq 3|awk -v v='a\ba' '{print NR==2?v:$0}'
1
a
3
$ seq 3|v='a\ba' awk '{print NR==2?ENVIRON["v"]:$0}'
1
a\ba
3
Both ENVIRON and -v are defined by POSIX.
Solution 6 - Sed
sed -e '8iProject_Name=sowstest' -i start using GNU sed
Sample run:
[root@node23 ~]# for ((i=1; i<=10; i++)); do echo "Line #$i"; done > a_file
[root@node23 ~]# cat a_file
Line #1
Line #2
Line #3
Line #4
Line #5
Line #6
Line #7
Line #8
Line #9
Line #10
[root@node23 ~]# sed -e '3ixxx inserted line xxx' -i a_file
[root@node23 ~]# cat -An a_file
1 Line #1$
2 Line #2$
3 xxx inserted line xxx$
4 Line #3$
5 Line #4$
6 Line #5$
7 Line #6$
8 Line #7$
9 Line #8$
10 Line #9$
11 Line #10$
[root@node23 ~]#
[root@node23 ~]# sed -e '5ixxx (inserted) "line" xxx' -i a_file
[root@node23 ~]# cat -n a_file
1 Line #1
2 Line #2
3 xxx inserted line xxx
4 Line #3
5 xxx (inserted) "line" xxx
6 Line #4
7 Line #5
8 Line #6
9 Line #7
10 Line #8
11 Line #9
12 Line #10
[root@node23 ~]#
Solution 7 - Sed
Perl solutions:
quick and dirty:
perl -lpe 'print "Project_Name=sowstest" if $. == 8' file
-lstrips newlines and adds them back in, eliminating the need for "\n"-ploops over the input file, printing every line-eexecutes the code in single quotes
$. is the line number
equivalent to @glenn's awk solution, using named arguments:
perl -slpe 'print $s if $. == $n' -- -n=8 -s="Project_Name=sowstest" file
-senables a rudimentary argument parser--prevents -n and -s from being parsed by the standard perl argument parser
positional command arguments:
perl -lpe 'BEGIN{$n=shift; $s=shift}; print $s if $. == $n' 8 "Project_Name=sowstest" file
environment variables:
setenv n 8 ; setenv s "Project_Name=sowstest"
echo $n ; echo $s
perl -slpe 'print $ENV{s} if $. == $ENV{n}' file
ENV is the hash which contains all environment variables
Getopt to parse arguments into hash %o:
perl -MGetopt::Std -lpe 'BEGIN{getopt("ns",\%o)}; print $o{s} if $. == $o{n}' -- -n 8 -s "Project_Name=sowstest" file
Getopt::Long and longer option names
perl -MGetopt::Long -lpe 'BEGIN{GetOptions(\%o,"line=i","string=s")}; print $o{string} if $. == $o{line}' -- --line 8 --string "Project_Name=sowstest" file
Getopt is the recommended standard-library solution.
This may be overkill for one-line perl scripts, but it can be done
Solution 8 - Sed
For those who are on SunOS which is non-GNU, the following code will help:
sed '1i\^J
line to add' test.dat > tmp.dat
- ^J is inserted with ^V+^J
- Add the newline after '1i.
- \ MUST be the last character of the line.
- The second part of the command must be in a second line.
Solution 9 - Sed
sed -i "" -e $'4 a\\\n''Project_Name=sowstest' start
- This line works fine in macOS
Solution 10 - Sed
it is working fine in linux to add in 2 lines.
sed '2s/$/ myalias/' file
Solution 11 - Sed
Thank you umläute
sed -i "" -e $'4 a\\\n''Project_Name=sowstest' filename
the following was usefull on macOS to be able to add a new line after the 4
In order to loop i created an array of folders, ti iterate on them in mac zsh
for foldercc in $foldernames;
sed -i "" -e $'4 a\\\n''Project_Name=sowstest' $foldercc/filenames;