Using a shell script to add a ‘</pre>’ after the last line in a large file

I need a SED, or AWK, command to find the last line in a file, and add </pre> to it.

Such as:

LINELINELINE

Changes to:

LINELINELINE</pre>

Lee Ikard

Posted 2016-06-22T03:21:54.483

Reputation: 45

Answers

You can also use what is known as a compound command. That's a list of commands, which the shell treats as a single command for the purpose of anything external to the compound command.

Yes, that's somewhat of a recursive definition; an example makes it easier to understand.

For example, to surround a file with <pre> and </pre>, you might use a command like:

( printf '<pre>' ; cat originalfile ; printf '</pre>' ) > newfile

If you don't have a temporary file, but rather want to surround the output of some command with something else, you can inject that command instead of the cat:

( printf '<pre>' ; find / -type d -print ; printf '</pre>' ) > somefile

This all works by applying the redirection to the output of the whole compound command, instead of just its parts.

Of course, this doesn't use sed or awk as requested, but for this sort of task, going to those tools is quite overkill.

a CVn

Posted 2016-06-22T03:21:54.483

Reputation: 26 553

This may work better for one-lining and simplicity, and the fact that I have a temp file would work better for this. I am going to try it, and then see results. – Lee Ikard – 2016-06-22T19:01:16.630

This worked better, for simplicity. – Lee Ikard – 2016-06-22T19:11:32.670

How about this:

echo "</pre>" >> /path/to/the/file

Or at the beginning is a bit trickier, you'd need to use a different file for the output.

echo "<pre>" | cat - /path/to/the/file > /path/to/the/newfile

cat means concatenate, and it has two arguments in this case: the - means stdin, so the first part of the concatenated file is whatever is piped to it (in this case the echo). The second argument is the file you want to prepend to. The concatenated files are then output to newfile.

Paul

Posted 2016-06-22T03:21:54.483

Reputation: 52 173

I just thought of something like that, thanks. Didn't know it was that simple. – Lee Ikard – 2016-06-22T03:29:04.757

Is there a way to do this to the beginning of the file? Since this seems to be the simpler (more readable) way than using sed. – Lee Ikard – 2016-06-22T10:30:08.647

Answer updated. – Paul – 2016-06-22T12:12:07.173

Useless use of echo? :-) cat <<<'<pre>' - /path/to/the/file Of course, that becomes rather more complicated if you want more than one string either at the beginning or the end. – a CVn – 2016-06-22T13:27:21.313

The echo isn't "useless", it is outputting the string. There may be alternative ways of doing this, but the absence of the command "echo" in this method would result in an error. I like your approach though. Aside form the useless use of printf where echo would suffice :) upvoted. – Paul – 2016-06-22T13:54:13.820

@Paul At least I didn't use a format string for printf. – a CVn – 2016-06-22T19:44:38.177

With (GNU) sed (as per the tag in the question):

$ sed -i -e '$a\</pre>' file.in

This will add a line with </pre> on it to file.in.

Alternatively:

$ sed -i -e '$s@\(.*\)@\1</pre>@' file.in

This will add </pre> to the last line in file.in.

Kusalananda

Posted 2016-06-22T03:21:54.483

Reputation: 1 941