Use a variable in a sed command

Question

I can\'t seem to use a variable in a sed command, for example:

sed \"24s/.*/\"$ct_tname\"/\" file1.sas > file2.sas

I want $ct_tnam

Answer 1

The problem is that when $ct_fname is substituted, sed sees extra / separators, so

sed "24s/.*/"$ct_tname"/" file1.sas > file2.sas

becomes

sed "24s/.*/"%let outputfile=/user/ct_ARGUMENT1.csv;"/" file1.sas > file2.sas

and you'll get a sed error because there are 5 / instead of the expected 3.

Instead, change your sed separators to an unused character like | or :, and either single or double quotes will work just fine:

sed '24s|.*|'$ct_tname'|' file1.sas > file2.sas
sed "24s|.*|"$ct_tname"|" file1.sas > file2.sas

Answer 2

you need to use double quotes (") instead of single quotes ('). single quotes pass their content literally, without translating variables (expansion).

try

sed "24s/.*/\"$ct_tname\"/" file1.sas > file2.sas

btw, if you're going to be editing a file (that is if file2.sas is a temporary file), you should be using ed instead.

Answer 3

You need to use double (") quotes, with single (') quotes the value of the variable doesn't get replaced. Since you have double quotes in your replacement text, you need to escape them:

sed "24s/.*/\"$ct_tname\"/" file1.sas > file2.sas

Answer 4

In my case, i just remplaced single quotes by the double ones:

for a in $(cat ext.cnf); do sed -n "/$a$/p" file1 >> file2; done

For now, it's working well...

Answer 5

Other answers focus on the use of escaped double quotes in their examples. Note that this is not always what you want :

$ FOO="auie"; echo foo123bar|sed "s/123/\"$FOO\"/"
foo"auie"bar
$ FOO="auie"; echo foo123bar|sed "s/123/$FOO/"
fooauiebar
$ FOO="auie"; echo fooauiebar|sed "s/\"$FOO\"/123/"
fooauiebar
$ FOO="auie"; echo fooauiebar|sed "s/$FOO/123/"
foo123bar

Answer 6

Shell variables are not expanded inside single quotes. Try this instead:

sed "24s/.*/\"$ct_tname\"/" file1.sas > file2.sas