How do insert lines of text into file after a particular line in unix

Question

How do insert lines of text into file after a particular line in unix ?

Background: The file is an autogenerated textfile but I manually have to edit it every time it is regenerated to add in 4 additional lines after a particular line. I can gurantee that this line will always be in the file but I cannot guarantee excalty what line it will be on so I want the additional lines to be added on the basis of the position of this line rather than adding to a fixed rownumber. I want to automate this process as it is part of my build process.

I'm using Mac OSX so I can make use of unix comand line tools, but Im not very familiar with such tools and cannot work out how to do this.

EDIT

Thanks for the solution, although I havent managed to get them working yet:

I tried Sed solution

sed -i '/<string>1.0</string>/ a <key>CFBundleHelpBookFolder</key>\
<string>SongKongHelp</string>\
<key>CFBundleHelpBookName</key>\
<string>com.jthink.songkong.Help</string>
' /Applications/SongKong.app/Contents/Info.plist

but get error

sed: 1: "/Applications/SongKong. ...": invalid command code S

and I tried the bash solution

#!/bin/bash

    while read line; do
      echo "$line"
      if [[ "$line" = "<string>1.0</string>"]]; then
        cat mergefile.txt    # or echo or printf your extra lines
      fi
    done < /Applications/SongKong.app/Contents/Info.plist

but got error

./buildosx4.sh: line 5: syntax error in conditional expression: unexpected token `;'
./buildosx4.sh: line 5: syntax error near `;'
./buildosx4.sh: line 5: `  if [[ "$line" = "<string>1.0</string>"]]; then'

EDIT 2 Now working, i was missing a space

#!/bin/bash

    while read line; do
      echo "$line"
      if [[ "$line" = "<string>1.0</string>" ]]; then
        cat mergefile.txt    # or echo or printf your extra lines
      fi
    done < /Applications/SongKong.app/Contents/Info.plist

***How*** is this file auto-generated? Can you fix the generator? — johnsyweb, Feb 16 '13 at 12:04
No I cant, the generator is not provided by me, maybe in the longterm it will be fixed (I have raised an issue ) but not in the short term. — Paul Taylor, Feb 16 '13 at 12:12

tripleee · Answer 1 · 2013-02-16T13:02:34.153

2

Assuming the marker line contains fnord and nothing else;

awk '1;/^fnord$/{print "foo"; print "bar";
    print "baz"; print "quux"}' input >output

edited Feb 16 '13 at 13:02

answered Feb 16 '13 at 12:14

tripleee

175,061
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+1 for the approach but you need a semi-colon after 1. – Ed Morton Feb 16 '13 at 12:59
+1, but can be simpler: `printf "foo\nbar\n"` or even `system( "cat repl-file" )` – William Pursell Feb 16 '13 at 14:39

user340140 · Answer 2 · 2013-02-16T12:29:34.933

0

use the sed 'a command with a regex for the line you need to match

sed -i '/the target line looks like this/ a this is line 1\
this is line 2\
this is line 3\
this is line 4
' FILENAME

edited Feb 16 '13 at 12:29

answered Feb 16 '13 at 12:20

user340140

628
6
10

I like this solution except I liked ghotis solution of keeping the lines in another file, can your solution be amended to take the 4 lines from a file ? – Paul Taylor Feb 16 '13 at 13:17
Its failing for me with error sed: 1: "/Applications/SongKong. ...": invalid command code S – Paul Taylor Feb 16 '13 at 13:56
1

This fails for Paul because `-i` is not standard `sed`. It works in gnu `sed`, but not all `sed`. – William Pursell Feb 16 '13 at 14:34
@William Pursell - thankyou this seems to be the main problem with unix, especially linux – Paul Taylor Feb 16 '13 at 15:08
The problem is not with unix, but with users not paying attention to standards. Linux is not unix. – William Pursell Feb 16 '13 at 15:59
If your search string contains a slash, you need to backslash-escape it, or use an alternate separator. `sed '\%1\.0% a...` – tripleee Feb 16 '13 at 18:42

score 0 · Answer 3 · answered Feb 16 '13 at 12:25

The problem can be solved efficiently for any filesize by this algorithm:

Read each line from the original file and print it to a tempfile.
If the last line was the marker line, print your insertion lines to the tempfile
Print the remaining lines
Rename the tempfile to the original filename.

As a Perl script:

#!perl
use strict; use warnings;

$^I = ".bak"; # create a backup file

while (<>) {
  print;
  last if /regex to determine if this is the line/;
}

print <<'END';
Yourstuff
END

print while <>; # print remaining lines
# renaming automatically done.

Testfile:

foo
bar
baz
qux
quux

Regex is /^ba/.

Usage: $ perl this_script.pl source-file

The testfile after processing:

foo
bar
Yourstuff
baz
qux
quux

You should probably escape the target regex to avoid meta characters being evaluated. — TLP, Feb 16 '13 at 14:31

ghoti · Accepted Answer · 2013-02-16T13:08:50.997

Another way to look at this is that you want to merge two files at some point in one of the files. If your extra four lines were in a separate file, you could make a more generic tool like this:

#!/usr/bin/awk

BEGIN {
  SEARCH=ARGV[1];    # Get the search string from the command line
  delete ARGV[1];    # Delete the argument, so subsequent arguments are files
}

# Collect the contents of the first file into a variable
NR==FNR { 
  ins=ins $0 "\n";
  next;
}

1    # print every line in the second (or rather the non-first) file

# Once we're in the second file, if we see the match, print stuff...
$0==SEARCH {
  printf("%s", ins);    # Using printf instead of print to avoid the extra newline
  next;
}

I've spelled this out for ease of documentation; you could obviously shorten it to something that looked more like triplee's answer. You'd invoke this like:

$ scriptname "Text to match" mergefile.txt origfile.txt > outputfile.txt

Done this way, you'd have a tool that could be used to achieve this kind of merge on different files and with different text.

Alternately, you could of course do this in pure bash.

#!/bin/bash

while read line; do
  echo "$line"
  if [[ "$line" = "matchtext" ]]; then
    cat mergefile.txt    # or echo or printf your extra lines
  fi
done < origfile.txt

Tried your script but got error ./buildosx4.sh: line 5: syntax error in conditional expression: unexpected token `;' ./buildosx4.sh: line 5: syntax error near `;' ./buildosx4.sh: line 5: ` if [[ "$line" = "1.0"]]; then' — Paul Taylor, Feb 16 '13 at 13:15
@PaulTaylor - I see from your updated question that you're missing the space before the `]]`. You need that space. — ghoti, Feb 16 '13 at 14:40

How do insert lines of text into file after a particular line in unix

4 Answers4