On 12/19/2014 07:46 AM, Maarten Billemont wrote: > Is there a particular reason why bash's built-in printf does not support > this format modifier?
Because POSIX does not require it to. printf(1) is only required to have a subset of printf(3) functionality: http://pubs.opengroup.org/onlinepubs/9699919799/utilities/printf.html http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap05.html#tag_05 That subset does not include $ reordering. > Does bash re-implement printf or does it use the > Standard C Library's printf? (If the former; why?) A combination - it MUST parse the string itself (because POSIX requires printf(1) to understand %b, but %b is not part of printf(3)), but then calls into the system's printf family as appropriate. And you'd be shocked at how many libc have bugs of one form or another in their printf(3) (even glibc's printf could cause a core dump when using %A on certain long double bit values, until earlier this year). -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
