How to concatenate stdin and a string?

I'm often using pipes, so this tends to be an easy way to prefix and suffix stdin:

echo -n "my standard in" | cat <(echo -n "prefix... ") - <(echo " ...suffix")
prefix... my standard in ...suffix

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.

A bit hacky, but this might be the shortest way to do what you asked in the question (use a pipe to accept stdout from echo "input" as stdin to another process / command:

echo "input" | awk '{print $1"string"}'

Output:

inputstring

What task are you exactly trying to accomplish? More context can get you more direction on a better solution.

Update - responding to comment:

@NoamRoss

The more idiomatic way of doing what you want is then:

echo 'http://dx.doi.org/'"$(pbpaste)"

The $(...) syntax is called command substitution. In short, it executes the commands enclosed in a new subshell, and substitutes the its stdout output to where the $(...) was invoked in the parent shell. So you would get, in effect:

echo 'http://dx.doi.org/'"rsif.2012.0125"

use cat - to read from stdin, and put it in $() to throw away the trailing newline

echo input | COMMAND "$(cat -)string"

However why don't you drop the pipe and grab the output of the left side in a command substitution:

COMMAND "$(echo input)string"