From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfgang Denk Date: Sun, 15 Oct 2017 13:50:40 +0200 Subject: [U-Boot] 'filesize' env var - making U-Boot command more scriptable? In-Reply-To: References: Message-ID: <20171015115040.ECEB41202A0@gemini.denx.de> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Dear Tim, In message you wrote: > > Various U-Boot commands that deal with files/blobs end up setting the > 'filesize' env variable to be used for subsequent commands which is > very handy. I haven't found this documented anywhere but a scan of the > code looks like this is done by Documentation is certainly not perfect, but at least filesize gets mentioned in the U-Boot environment variables section of the manual; see the very end of [1] (plus a few othe rplaces). [1] http://www.denx.de/wiki/view/DULG/UBootEnvVariables > I've seen other commands that allow a usage that will allow specifying > a var name to put a result in. > > I've noticed commands such as 'ubi' and 'nand' would benefit from > setting filesize when dealing with volume names and partition names. > I've also noticed how some commands (ie nand) are good about reporting > sizes in hex but others (ie ubi) report them in decimal only making it > difficult for someone to even cut-and-paste sizes to following > commands. > > Has there been a desire or proposal to make this more standard or come > up with something different? If you really think about it, all of this is just a worarounf for the lack of command substitution (aka backquotes / backticks) in the available command interpreters in U-Boot. The currently most used one is based on an ancient version of hush from the BusyBox project. It has a large number of severe restrictions and a fair number of known other issues. IMO if somebody is willing to spend efforts in this area it would be best to replace hust by a more recent version of a shell, adding command substitution. [If you go a step further you might even think about introducing a concept of "files" and adding pipes. But then we would be mioving more and more into the direction of an OS ;-) ] Best regards, Wolfgang Denk -- DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de All this doesn't alter anything, you know. The world is still full of stupid people. They don't use their brains. They don't seem to want to think straight. - Terry Pratchett, _Soul Music_