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.