[BusyBox] overriding builtins
David Douthitt
ssrat at mailbag.com
Fri Nov 17 15:01:02 UTC 2000
On 17 Nov 2000, at 9:07, Tomi Ollila wrote:
> Thursday Nov 16 16:35:30 -0800 2000 Larry Doolittle <ldoolitt at recycle.lbl.gov> wrote:
> I'm reading throught zsh manual page (zshall and searching for `builtin')
> to check how zsh can be forced to execute external command instead of a
> builtin if one exists. So far I've found one:
>
> command
> The command word is taken to be the name of an external
> command, rather than a shell function or builtin.
>
> i.e. `command echo foo' will use external echo.
ksh (really pdksh) has this:
command [-pvV] cmd [arg1 ...]
If neither the -v nor -V options are given, cmd is
executed exactly as if the command had not been
specified, with two exceptions: first, cmd cannot
be a shell function, and second, special built-in
commands lose their specialness (i.e., redirection
and utility errors do not cause the shell to exit,
and command assignments are not permanent). If the
-p option is given, a default search path is used
instead of the current value of PATH (the actual
value of the default path is system dependent: on
POSIXish systems, it is the value returned by
getconf CS_PATH
).
If the -v option is given, instead of executing
cmd, information about what would be executed is
given (and the same is done for arg1 ...): for spe
cial and regular built-in commands and functions,
their names are simply printed, for aliases, a com
mand that defines them is printed, and for commands
found by searching the PATH parameter, the full
path of the command is printed. If no command is
be found, (i.e., the path search fails), nothing is
printed and command exits with a non-zero status.
The -V option is like the -v option, except it is
more verbose.
Bash says this:
command [-pVv] command [arg ...]
Run command with args suppressing the normal shell
function lookup. Only builtin commands or commands
found in the PATH are executed. If the -p option
is given, the search for command is performed using
a default value for PATH that is guaranteed to find
all of the standard utilities. If either the -V or
-v option is supplied, a description of command is
printed. The -v option causes a single word indi
cating the command or file name used to invoke com
mand to be printed; the -V option produces a more
verbose description. If the -V or -v option is
supplied, the exit status is 0 if command was
found, and 1 if not. If neither option is supplied
and an error occurred or command cannot be found,
the exit status is 127. Otherwise, the exit status
of the command builtin is the exit status of com
mand.
Just FYI....
Perhaps we should consider a new command for busybox: "command" ?
What ever happened to "env"?
--
David Douthitt
UNIX Systems Administrator
HP-UX, Linux, Unixware
ddouthitt at mennonite.minister.net
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