The bash built-in type can be used for this purpose by checking its exit status: Exit Status: Returns success if all of the NAMEs are found; fails if any are not found. How portable is it? The ...
Occasionally I need to specify a "path-equivalent" of one of the standard IO streams (stdin, stdout, stderr). Since 99% of the time I work with Linux, I just prepend /dev/ to get /dev/stdin, etc., ...