BASH - SED insert new line before last, containing tab and variable

Question

I'm trying to insert a new line into a file just before the last line. The new line includes tab and a variable.

Using the following. This inserts the line at the correct place, includes the tab but doesn't expand the variable.

sed '$i \\tnewline = $newvalue' file

If I wrap it in double quotes instead of single quotes I get errors. sed: -e expression #1, char 13: unterminated address regex

How do I do this ?

Thanks

please update the question with a sample input file, the output from `typeset -p newvalue` and the (correct) expected output — markp-fuso, Sep 24 '21 at 14:47
It is not about difference in single and double quotes as OP has already tried double quotes. As per OP: `If I wrap it in double quotes instead of single quotes I get errors. sed: -e expression #1, char 13: unterminated address regex` — anubhava, Sep 25 '21 at 08:40

score 3 · Accepted Answer · answered Sep 24 '21 at 14:47

3

You may use this sed:

sed "\$i \\\\tnewline = $newvalue" file

Difference is escaping first $ when we use double quotes and use of \\\\t instead of \\t due to expansion of double quotes in shell.

answered Sep 24 '21 at 14:47

anubhava

1

Perfect thanks for explaining why the additional slashes are needed. – Tom Sep 24 '21 at 14:53

1 Answers1