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What is the difference between autoload -U and plain autoload?
For instance, here it is recommended to run:
autoload -U run-help
autoload run-help-git
autoload run-help-svn
autoload run-help-svk
unalias run-help
alias help=run-help
Why is -U only in the first line?
Yes, you do see the recommendation for -U often, usually paired with -z. It’s not documented in the run-help for autoload, but there is a section titled “AUTOLOADING FUNCTIONS” in the manpage for zshmisc.
There it states:
The usual alias expansion during reading will be suppressed if the autoload builtin or its equivalent is given the option -U. This is recommended for the use of functions supplied with the zsh distribution. Note that for functions precompiled with the zcompile builtin command the flag -U must be provided when the .zwc file is created, as the corresponding information is compiled into the latter.
I read that as “disregard aliases”. The -z seems to be to avoid Ksh-isms. I just memorize -Uz and usually add them to any autoload. Maybe a worthwhile alias: alias al=’autoload -Uz’.
See also: https://stackoverflow.com/questions/12570749/zsh-completion-difference
-z as well? I barely find any reference on the Internet about what's going on related to "avoid Ksh-isms".
-z option loads functions as if the KSH_FUNCTIONS option were unset, and the -k option loads functions as if it were set, regardless of whether the option is set. That is, -z disables "Ksh-style" autoloading, and -k enables it. The difference between these two is described in manual section 9.1 - "Autoloading Functions". Ksh-style basically just sources the file, while Zsh-style has some extra behavior that allows the function definition file to also be used as a standalone executable script.
Mar 16 at 14:37
autoload builtin itself and its flags are documented in section 17 - "Shell Builtin Commands", and the KSH_AUTOLOAD option is documented in section 16.2.10 - "Shell Emulation.
Mar 16 at 14:37
-U is only used in the first invocation and not the others. I've been using -Uz by default for all of my own functions, because I never want alias expansion during evaluation and I always write Zsh-style function files. KSH_FUNCTIONS is disabled by default and I don't enable it in my own config, so -z is probably redundant, but it can't hurt either.
Mar 17 at 14:44