How to concatenate stdin and a string?

Question

How to I concatenate stdin to a string, like this?

echo \"input\" | COMMAND \"string\"

and get

inputstring

Answer 1

There are some ways of accomplish this, i personally think the best is:

echo input | while read line; do echo $line string; done

Another can be by substituting "$" (end of line character) with "string" in a sed command:

echo input | sed "s/$/ string/g"

Why i prefer the former? Because it concatenates a string to stdin instantly, for example with the following command:

(echo input_one ;sleep 5; echo input_two ) | while read line; do echo $line string; done

you get immediatly the first output:

input_one string

and then after 5 seconds you get the other echo:

input_two string

On the other hand using "sed" first it performs all the content of the parenthesis and then it gives it to "sed", so the command

(echo input_one ;sleep 5; echo input_two ) | sed "s/$/ string/g"

will output both the lines

input_one string
input_two string

after 5 seconds.

This can be very useful in cases you are performing calls to functions which takes a long time to complete and want to be continuously updated about the output of the function.