[Haifux] [HAIFUX LECTURE] Command-line utilities: Tips and tricks (part II) -- Eli Billauer

[Oleg Goldshmidt]

Daniel Shahaf <d.s at daniel.shahaf.name> writes:

> Sure.  It's a zsh-specific syntax for an anonymous function with
> arguments.  In effect it's an anonymous block.  For example:
>
> % (){ printf "$1\n" 04 } "%s"  
> 04
> % (){ printf "$1\n" 04 } "%d"  
> 4
> % (){ printf "$1\n" 04 } "%e"  
> 4.000000e+00
>
> In interactive usage I sometimes find myself wanting to run a command
> several times in a row with one argument changed.  When that argument is
> in the middle of a (potentially multi-line) command, I find it easier to
> change it between runs by using an ad-hoc anonymous function to move the
> argument-to-be-changed to the end of the input.  Another case where that
> would be useful is when the argument appears in two places in the
> command --- using an anonymous function allows changing the argument in
> just one place rather than two.

In bash, I use fc ("fix command") for this:

$ printf "%s\n" 04
04
$ fc -s %s=%d
printf "%d\n" 04
4
$ fc -s %d=%e
printf "%e\n" 04
4.000000e+00

Very useful. Check out also 

$ fc -n -3 -1

or similar to edit the last 3 commnds (with $EDITOR, or use -e) 
and execute them when done editing.

-- 
Oleg Goldshmidt | pub at goldshmidt.org