2020-02-19 11:52:21 +0100, Joerg Schilling: [...] > > $ zsh -c 'time -p uname | cat' > > zsh:1: command not found: -p > > BTW: I remember that you frequently write that zsh intends to emulate the csh > behavior, but csh _is_ able to get timing for builtin commands: > > csh > % time alias > 0.0u 0.0s 0:00 0% 0+0k 0+0io 0pf+0w > % [...]
Like I said, csh forks there to be able to report the usage: tcsh> alias a b tcsh> alias a b tcsh> time alias c d 0.000u 0.000s 0:00.00 0.0% 0+0k 0+0io 0pf+0w tcsh> alias a b (missing "c d" in that output as alias c d was run in a subshell). zsh does have a csh emulation mode (emulate csh), which makes it more csh-like, but there's no way it could be twisted into being a csh interpreter. That's more of a helper mode to make it more friendly to users who come from tcsh. Like ksh or bash, zsh got many features from csh. Of the three shells, it's probably the one which got the most (like it's the one which got the most features from rc, or more generally the most features). Here, when it comes to time, it got the full getrusage() from csh/BSD, it extended it by timing each pipeline component separately (very useful to spot bottlenecks). Like csh, it report *process* resource usage. Contrary to csh, it supports timing pipelines, compounds, functions (csh has no functions anyway). And like I said, contrary to csh, it doesn't implicitly add an extra fork. That would change the functionality and would not be practical given the point above. That does mean it can't report resource usages of things that are not run in a separate process. That's a sometimes annoying drawback (though some easy workaround), but that's a tradeoff. -- Stephane
