Question

I need some help with sed regex substitution.

From the following line:

Provides          mysql                

I want to get:

Provides          mysql-5.5                

The best solution I was able to come with is:

sed -i "s/\(Provides\)\(\s\)*\(mysql\)/\1\2mysql-5.5/g" my_file_containing_the_line

but the result is not as I want:

Provides mysql-5.5                

Which is not perfect because I lost the white spaces between “Provides” and “mysql-5.5”

Thanks

Answer 1

"s/\(Provides\)\(\s\)*\(mysql\)/\1\2mysql-5.5/g"

\2 group does not contain all spaces

"s/\(Provides\)\(\s*\)\(mysql\)/\1\2mysql-5.5/g" will work.

$> echo "Provides          mysql" | sed "s/\(Provides\)\(\s*\)\(mysql\)/\1\2mysql-5.5/g"
Provides          mysql-5.5

Beside that you can use --regexp-extended option to suppress redundant escaping:

$> echo "Provides          mysql" | sed --regexp-extended "s/(Provides)(\s*)(mysql)/\1\2mysql-5.5/g"
Provides          mysql-5.5

Or even

$> echo "Provides          mysql" | sed --regexp-extended "s/(Provides\s*)(mysql)/\1\2-5.5/g"
Provides          mysql-5.5