What is the proper way to insert tab in sed?

Question

What is the proper way to insert tab in sed? I'm inserting a header line into a stream using sed. I could probably do a replacement of some character afterward to put in tab using regular expression, but is there a better way to do it?

For example, let's say I have:

some_command | sed '1itextTABtext'

I would like the first line to look like this (text is separated by a tab character):

text    text

I have tried substituting TAB in the command above with "\t", "\x09", " " (tab itself). I have tried it with and without double quotes and I can't get sed to insert tab in between the text.

I am trying to do this in SLES 9.

Answer 1

Sed can do this, but it's awkward:

% printf "1\t2\n3\t4\n" | sed '1i\\
foo bar\\
'
foo bar
1   2
3   4
$

(The double backslashes are because I'm using tcsh as my shell; if you use bash, use single backslashes)

The space between foo and bar is a tab, which I typed by prepending it with CtrlV. You'll also need to prepend the newlines inside your single quotes with a CtrlV.

It would probably be simpler/clearer to do this with awk:

$ printf "1\t2\n3\t4\n" | awk 'BEGIN{printf("foo\tbar\n");} {print;}'

Answer 2

You can simply use the sed i command correctly:

some_command | sed '1i\
text    text2'

where, as I hope it is obvious, there is a tab between 'text' and 'text2'. On MacOS X (10.7.2), and therefore probably on other BSD-based platforms, I was able to use:

some_command | sed '1i\
text\ttext2'

and sed translated the \t into a tab.

If sed won't interpret \t and inserting tabs at the command line is a problem, create a shell script with an editor and run that script.

Answer 3

escape the tab character:

sed -i '/<setup>/ a \\tmy newly added line' <file_name>

NOTE: above we have two backslashes (\) first one is for escaping () and the next one is actual tab char (\t)

Answer 4

As most answers say, probably literal tab char is the best.

info sed saying "\t is not portable." :

... '\CHAR' Matches CHAR, where CHAR is one of '$', '*', '.', '[', '\', or '^'. Note that the only C-like backslash sequences that you can portably assume to be interpreted are '\n' and '\'; in particular '\t' is not portable, and matches a 't' under most implementations of 'sed', rather than a tab character. ...

Answer 5

I found an alternate way to insert a tab by using substitution.

some_command | sed '1s/^/text\ttext\n/'

I still do not know of a way to do it using the insert method.

Answer 6

Assuming bash (and maybe other shells will work too):

some_command | sed $'1itext\ttext'

Bash will process escapes, such as \t, inside $' ' before passing it as an arg to sed.