I Want add some line in a file at linux

Question

I have a linux centos 7 server and i want Below lines to file with name config.xml

<vhostMap>
  <vhost>google</vhost>
  <domain>google.com, www.google.com</domain>
</vhostMap>

i want add this lines after line 8 at config.xml file

how its possible with sed or awk command? its python or perl? i have searched much, but its hard for me as im noob, can someone tell me some example?

Thanks.

Maybe [this](https://stackoverflow.com/questions/46431161/add-a-line-in-a-specific-position-with-linux-and-output-to-the-same-file) can help you. — Daniel Ocando, Mar 07 '20 at 11:34
[sed](http://www.yourownlinux.com/2015/04/sed-command-in-linux-append-and-insert-lines-to-file.html) approach — Polar Bear, Mar 07 '20 at 23:36

Błotosmętek · Accepted Answer · 2020-03-07T11:42:26.097

1

In Python it is easy:

to_add = """<vhostMap>
  <vhost>google</vhost>
  <domain>google.com, www.google.com</domain>
</vhostMap>
"""
with open("config.xml", "r") as f:
    all_lines = f.readlines()
with open("config.xml", "w") as f:
    for l in all_lines[:8]: f.write(l)
    f.write(to_add)
    for l in all_lines[8:]: f.write(l)

edited Mar 07 '20 at 11:42

answered Mar 07 '20 at 11:28

Błotosmętek

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1

Note that there is a race condition here. If the process is terminated after the 2nd open and before the final write is complete, data may be lost. – William Pursell Mar 07 '20 at 11:29
@WilliamPursell the only workaround I can think of is to write to a temporary file and then replace the original with the temporary one, but this might be overcomplicating things. – Błotosmętek Mar 07 '20 at 11:37
i just did this: nano test.py and paste your code on it, then run it using python test.py then i see below output: Traceback (most recent call last): File "test.py", line 9, in f.write(all_lines[:8]) TypeError: expected a character buffer object – antonio jose de maia santos Mar 07 '20 at 11:38
Sorry, my mistake. Corrected. – Błotosmętek Mar 07 '20 at 11:42
@Błotosmętek yes,now it works, Thanks, can i ask why you did not do this with sed or awk command? – antonio jose de maia santos Mar 07 '20 at 11:48
@antoniojosedemaiasantos because I need more Python practice :-) – Błotosmętek Mar 07 '20 at 11:51

score 1 · Answer 2 · answered Mar 07 '20 at 21:45

The easiest way for me to do it with shell commands is to show the head 8 lines of original config.xml and deviate the output to a new file. Then append the newfile with your code and finally including the tail of config.xml starting from line 8

$ head -n 8 config.xml > newconfig.xml
$ cat your_code.txt >> newconfig.xml
$ tail -n+8 config.xml >> newconfig.xml

Finally you can substitute original config.xml with newfile. Check the content of config.xml before doing it!

$ mv newconfig.xml config.xml

score 1 · Answer 3 · answered Mar 07 '20 at 23:12

In perl such operation can be easily achieved in numerous ways, feel free to choose one which you find favorable

Substitute approach

use strict;
use warnings;
use feature 'say';

my $filename = 'config.xml';

my $insert = 
'<vhostMap>
  <vhost>google</vhost>
  <domain>google.com, www.google.com</domain>
</vhostMap>';

open my $fh, '<', $filename
    or die "Couldn't open $filename: $!";

my $data = do{ local $/; <$fh> };

close $fh;

$data =~ s/((.*?\n){8})/${1}$insert\n/s;

open $fh, '>', $filename
    or die "Couldn't open $filename: $!";

say $fh $data;

close $fh;

Array slice approach

use strict;
use warnings;
use feature 'say';

my $filename = 'config.xml';

my $insert = '<vhostMap>
  <vhost>google</vhost>
  <domain>google.com, www.google.com</domain>
</vhostMap>';

open my $fh, '<', $filename
    or die "Couldn't open $filename: $!";

my @lines = <$fh>;

close $fh;

open $fh, '>', $filename
    or die "Couldn't open $filename: $!";

say $fh @lines[0..7],$insert,"\n",@lines[8..$#lines];

close $fh;

Array iteration approach

use strict;
use warnings;
use feature 'say';

my $filename = 'config.xml';

my $insert = '<vhostMap>
  <vhost>google</vhost>
  <domain>google.com, www.google.com</domain>
</vhostMap>';

open my $fh, '<', $filename
    or die "Couldn't open $filename: $!";

my @lines = <$fh>;

close $fh;

open $fh, '>', $filename
    or die "Couldn't open $filename: $!";

my $line_count = 0;

for (@lines) {
    chomp;
    $line_count++;      
    say $fh $_; 
    say $fh $insert if $line_count == 8;
}

close $fh;

Input

line 1
line 2
line 3
line 4
line 5
line 6
line 7
line 8
line 9
line 10
line 11
line 12

Output

line 1
line 2
line 3
line 4
line 5
line 6
line 7
line 8
<vhostMap>
  <vhost>google</vhost>
  <domain>google.com, www.google.com</domain>
</vhostMap>
line 9
line 10
line 11
line 12

I Want add some line in a file at linux

3 Answers3