How do I access a reserved word if an alias is hiding it?
Here if works normally:
% if : ; then echo true; fi
true
After aliasing if:
% alias if=date
% if : ; then echo true; fi
zsh: parse error near `then'
Prefixing with builtin or \ doesn't help:
% builtin if : ; then echo true; fi
zsh: parse error near `then'
% \if : ; then echo true; fi
zsh: parse error near `then'
How do I access a reserved word in the pathological case that it hidden by an alias?
schily's answer pointed me to POSIX Shell Command Language section 2.3.1 which says:
However, reserved words in correct grammatical context shall not be candidates for alias substitution.
I've confirmed that both bash and zsh default behaviour doesn't follow the above.
I asked on zsh-workers and was directed to the option POSIX_ALIASES, about which the man page says:
POSIX_ALIASES <K> <S>When this option is set, reserved words are not candidates for alias expansion: it is still possible to declare any of them as an alias, but the alias will never be expanded. Reserved words are described in the section RESERVED WORDS in zshmisc(1).
Try to use a shell that does not have this bug.
The standard says that a reserved word cannot be subject to alias expansion.
So:
alias if=echo
if : ; then echo true; fi
prints true with correctly written shells.
Unfortunately, bash is not correct here too, but ksh93, bosh and dash behave correctly.
To give further hints:
a backslash before an alias name disables this alias in correctly written shells.
a backslash before a reserved word, makes this token a normal word.
As a result \if disables the alias but at the same time makes it a non-reserved word.
\if doesn't work in zsh. It also doesn't work in bash. Any workarounds for those shells?
\if does not work. Since if is not a builtin but part of the syntax, your builtin call cannot help. Do you have a real world problem this question is based on?
zsh global aliases as they were causing syntax errors in a sourced file. I came across this question while trying to avoid all aliases in the process of saving zsh option aliases and then setting no_aliases.
ifis a builtin incshbut not in Bourne Shell compatible shells.=doesn't help in either shell.