How to use argument twice in printf in shell?

Question

printf %s%s one two prints onetwo but I would like oneonetwotwo

How can I do that?

Answer 1

In zsh:

printf '%1$s%1$s' one two

Where %n$s is like %s except that it uses the n^th argument instead of the next one like the printf()¹ of the GNU libc (but not in the standalone GNU printf utility nor the printf builtin of the GNU shell (bash) yet).

That was added to zsh in 2001 and is also available in a few other printf implementations though with some variations and will be specified in the next version of the POSIX standard

Note that while printf '%s%1$s' one two would also work in zsh, it does not in all printf implementations that support %n$x and POSIX will make the behaviour unspecified if directives with and without n$ are mixed.

Another option is to use the array zipping operator, for instance in an anonymous function:

(){ printf %s%s ${argv:^argv}; } one two

Where with zip $argv with itself resulting in one one two two being passed to printf. As usual, change to "${(@)argv:^argv}" or "${@:^argv}" to preserve empty elements in any.

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^{That %$nX syntax in printf() is POSIX, possibly originating in SVR4 (was in SVR4, not SVR3), probably coming from nl_printf() earlier used for localisation of messages where the order of elements in a message may change from one language to the next.}