Single line heredocument - Possible in Bash?

Question

I desire to run a cat heredocument in a single row instead the natural syntax of 3 rows (opener, content, and delimiter). My need to do so is mostly aesthetic as the redirected content aimed aimed to be part of a handbook text file and I would like to save as much rows as I can, in that particular file).

Doing cat <<< TEST > ~/myRep/tiesto tiesto TEST (what I would normally split for 3 parts) results in an errors:

tiesto: No such file or direcotry

TEST: No such file or directory.

Is it even possible to execute one-row heredocuments in Bash?

Solution 1

Yes, but you'd be using a an here-string rather than a here-document:

cat >"$HOME/myRep/tiesto" <<<'tiesto'

This will send the string tiesto to cat on its standard input, and it will write the string to the file $HOME/myRep/tiesto through a redirection of its standard output.

Note that here-strings are not standard but are implemented by at least zsh (where it comes from, at the same time as the UNIX version of rc, though that rc and its derivatives like es or akanga don't add an extra newline character in the end), ksh93, bash, mksh and yash.

Solution 2

You could put a here-document (as opposed to a here-string), on a single line, by using:

eval $'cat << TEST > ~/myRep/tiesto\ntiesto\nTEST'

Technically, that's one line of code, but the $'...' will expand into a new 3 line code that is evaluated again.

Using eval, you can always put any shell code on one line.

With shells that don't support $'...', you can do:

eval "$(printf 'NL="\n"')"; eval "cat << TEST > ~/myRep/tiesto${NL}tiesto${NL}TEST"

Or

eval "$(printf 'cat << TEST > ~/myRep/tiesto\ntiesto\nTEST')"

Of course here,

echo tiesto > ~/myRep/tiesto

would be a lot simpler. Or for multiple lines:

printf '%s\n' "line 1" "line 2" > ~/myRep/tiesto

Comments

[KevinO]

Possible duplicate of Is it possible to do a here-document in one line or echo verbatim?

[Admin]

It seems to me his answer isn't focused on either heredocument or awk. I ask only on heredocuments.