How to add prefix/suffix to each line of a file?

Question

for example file1 contains:

entry1:value1
entry2:value2
entry3:value3

now I want to add a prefix "file1:" to each line:

file1:entry1:value1
file1:entry2:value2
file1:entry3:value3

How can I do that in one command line?

I'm using bash.
BTW, The leading space must be preserved, so bash built-in read line doesn't work for me.

Answer 1

% sed 's/^/file1:/' file1

Answer 2

read splits by $IFS, so you have to clear that first.

while IFS= read line
do
  echo "file1:$line"
done

Answer 3

awk equivalent of the sed answer

awk '{gsub(/^/,"file1:")}1' file

or just simply

awk '{$0="file:1"$0}1' file

Answer 4

Escaping special characters:

printf -v prefix %q 'ab\cd%;,: /{][}-+*'; prefix=${prefix////\\/}; sed "s/^/$prefix/" file

Answer 5

I using AWK, you can add pretty much any prefix:

awk -v PRE='anything:' '{$0=PRE$0; print}' file1

This will work even for fancy non-printable chars.