Question

I’m trying to write an alias for cd !!:1, which takes the 2nd word of the previous command, and changes to the directory of that name. For instance, if I type

rails new_project  
cd !!:1  

the second line will cd into the “new_project” directory.

Since !!:1 is awkward to type (even though it’s short, it requires three SHIFTed keys, on opposite sides of of the keyboard, and then an unSHIFTed version of the key that was typed twice SHIFTed), I want to just type something like

cd-  

but since the !!:1 is evaluated on the command line, I (OBVIOUSLY) can’t just do

alias cd-=!!:1  

or I’d be saving an alias that contained “new_project” hard-coded into it. So I tried

alias cd-='!!:1'  

The problem with this is that the !!:1 is NEVER evaluated, and I get a message that no directory named !!:1 exists. How can I make an alias where the history substitution is evaluated AT THE TIME I ISSUE THE ALIAS COMMAND, not when I define the alias, and not never?

(I’ve tried this in both bash and zsh, and get the same results in both.)

Answer 1

For zsh:

alias cd-='cd ${${(z)$(fc -l -1)}[3]}'

How this works:

1. $(fc -l -1) is evaluated. fc -l {start} [{end}] means «list history commands from {start} till {end} or last if {end} is not present».
2. ${(z)...} must split ... into an array just like the shell does (see «Parameter Expansion Flags» in man zshexpn), but in fact it splits on blanks. Maybe it is only my bug.
3. ${...[3]} takes third value from the array. First value is a number of a command, second is command and third and later are arguments.