On Mon, Jun 02, 2008 at 05:12:45PM +0100, Stephane Chazelas wrote: > On Mon, Jun 02, 2008 at 03:04:55PM +0000, Clint Adams wrote: > > On Mon, Jun 02, 2008 at 11:58:59AM +0100, Stephane Chazelas wrote: > > > Another strange requirement that I see no shell implements even > > > posh, is that if a builtin (such as "[" or "echo" or ":") is not > > > found in $PATH, its invocation should fail!?! > > > > Could you point me to that in the standard? > > This is so weird that I'm suspecting that either I misinterpret > it or I missed something. > > Here is the text, please tell me if you understand it > differently:
Hi Clint, > Given that I've never seen a /bin/: (as : is built in every > shell), that would imply that ":" would never work. ":" (colon) is a special built-in, so it was a bad example, but it is still true for "[", "echo", "printf"... Do you read me the same way as I do? > http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_09_01_01 > > SUS> Command Search and Execution > SUS> > SUS>If a simple command results in a command name and an optional list of > SUS>arguments, the following actions shall be performed: > SUS> > SUS> 1. If the command name does not contain any slashes, the first successful > SUS> step in the following sequence shall occur: > SUS> > SUS> a. If the command name matches the name of a special built-in > SUS> utility, that special built-in utility shall be invoked. > SUS> > SUS> b. If the command name matches the name of a function known to this > SUS> shell, the function shall be invoked as described in Function > SUS> Definition Command. If the implementation has provided a standard > SUS> utility in the form of a function, it shall not be recognized at > SUS> this point. It shall be invoked in conjunction with the path > SUS> search in step 1d. > SUS> > SUS> c. If the command name matches the name of a utility listed in the > SUS> following table, that utility shall be invoked. > SUS> > SUS> alias false jobs read wait > SUS> bg fc kill true > SUS> cd fg newgrp umask > SUS> command getopts pwd unalias > SUS> > SUS> > SUS> d. Otherwise, the command shall be searched for using the PATH > SUS> environment variable as described in the Base Definitions volume > SUS> of IEEE Std 1003.1-2001, Chapter 8, Environment Variables: > SUS> > SUS> i. If the search is successful: > SUS> > SUS> a. If the system has implemented the utility as a regular > SUS> built-in or as a shell function, it shall be invoked at > SUS> this point in the path search. > SUS> > SUS> b. Otherwise, the shell executes the utility in a separate > SUS> utility environment (see Shell Execution Environment) > SUS> with actions equivalent to calling the execve() function > SUS> as defined in the System Interfaces volume of > SUS> IEEE Std 1003.1-2001 with the path argument set to the > SUS> pathname resulting from the search, arg0 set to the > SUS> command name, and the remaining arguments set to the > SUS> operands, if any. > SUS> > SUS> If the execve() function fails due to an error > SUS> equivalent to the [ENOEXEC] error defined in the System > SUS> Interfaces volume of IEEE Std 1003.1-2001, the shell > SUS> shall execute a command equivalent to having a shell > SUS> invoked with the pathname resulting from the search as > SUS> its first operand, with any remaining arguments passed > SUS> to the new shell, except that the value of "$0" in the > SUS> new shell may be set to the command name. If the > SUS> executable file is not a text file, the shell may bypass > SUS> this command execution. In this case, it shall write an > SUS> error message, and shall return an exit status of 126. > SUS> > SUS> Once a utility has been searched for and found (either as a > SUS> result of this specific search or as part of an unspecified > SUS> shell start-up activity), an implementation may remember its > SUS> location and need not search for the utility again unless the > SUS> PATH variable has been the subject of an assignment. If the > SUS> remembered location fails for a subsequent invocation, the > SUS> shell shall repeat the search to find the new location for > SUS> the utility, if any. > SUS> > SUS> ii. If the search is unsuccessful, the command shall fail with > SUS> an exit status of 127 and the shell shall write an error > SUS> message. > > Given that I've never seen a /bin/: (as : is built in every > shell), that would imply that ":" would never work. -- Stéphane -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
