Le mercredi 12 janvier 2022, 21:03:40 CET Simon Glass a écrit :
Hi Francis,
On Fri, 31 Dec 2021 at 09:14, Francis Laniel
francis.laniel@amarulasolutions.com wrote:
In Busybox hush, '<' and '>' are used as redirection operators. For example, cat foo > bar will write content of file foo inside file bar. In U-Boot, we do not have file system, so we can hardly redirect command output inside a file.
But, in actual U-Boot hush, these operators ('<' and '>') are used as string compare operators. For example, test aaa < bbb returns 0 as aaa is before bbb in the dictionary. Busybox hush also permits this, but operators need to be escaped ('<' and '>'), so we stick here to this behavior. Also, if escaping is needed it permits the developer to think about its code, as in a lot of case, we want to compare integers (using '-lt' or '-gt') rather than strings.
Signed-off-by: Francis Laniel francis.laniel@amarulasolutions.com
common/cli_hush_2021_upstream.c | 28 +++++++++++++++++++++++++++- 1 file changed, 27 insertions(+), 1 deletion(-)
Reviewed-by: Simon Glass sjg@chromium.org
We should add a file interface to U-Boot. Is that the only impediment to implementing redirection? I thought the problem was lack of fork() ?
From my understanding of Busybox hush code dealing with I/O redirection (mainly parse_redirect() and struct redir_struct), it seems fork is never used here. So, if we add something to emulate file descriptor it should be OK to add this feature to U-Boot.
Regards, Simon