leah blogs: February 2011

It’s been almost three years since the last installment, so here is the next dollop of tips:

1. =(command) expands to a tempfile with the output of command that is deleted after the line has finished. In effect, the same as <(command) but allows applications to seek. E.g.:

   xpdf =(zcat foo.pdf.gz)
   

2. !-history-expansion is nice, but can be confusing if you have a command line with many ! that should be left alone. Either quote the ! with single quotes or write !" at the beginning of the line (yes, that " is left unclosed):

   % !" echo Hey there! Wow!!
   Hey there! Wow!!
   

3. An application of modifiers is !:t, which results into the basename of the last argument. Very useful when working with URLs, for example. You’ll never have to strip the path manually again:

   % wget ftp://ruby-lang.org/pub/ruby/1.8/ruby-1.8.7-p330.tar.gz
   % tar xzvf !:t
   

4. When playing with parameter expansion flags, it often is annoying having to use variables for immediate values:

   % foo=bar.c; echo ${foo:a:u}
   /HOME/CHRIS/BAR.C
   

   Instead of the ugly solution

   % echo ${$(echo bar.c):a:u}
   

   better use this:

   % echo ${${:-bar.c}:a:u}
   

   Here, ${:-bar.c} is an instance of the well-known ${FOO:-BAR} default substition operator.

5. To run a command several times, use repeat. Useful for benchmarks, e.g.:

   % repeat 3 time sleep 1
   sleep 1  0.00s user 0.00s system 0% cpu 1.002 total
   sleep 1  0.00s user 0.00s system 0% cpu 1.005 total
   sleep 1  0.00s user 0.00s system 0% cpu 1.002 total
   

6. Use glob modifiers to sort glob expansions. Helpful are: (om) (sort by modification time) or (n) (sort numerically):

   % pdfjoin chapter*.pdf(n) -o all.pdf
   

7. Another useful glob modifier is P, for example to prefix a flag:

   % tar czvf foo.tar.gz * *.tmp(P:--exclude:)
   

   (yes, tar can exclude patterns, but some other tools can’t, and zsh does patterns better anyway.)

8. Some ZLE hacks I use. To override default completion in various ways:

   # Force file name completion on C-x TAB, Shift-TAB.
   zle -C complete-files complete-word _generic
   zstyle ':completion:complete-files:*' completer _files
   bindkey "^X^I" complete-files
   bindkey "^[[Z" complete-files
   
   
   # Force menu on C-x RET.
   zle -C complete-first complete-word _generic
   zstyle ':completion:complete-first:*' menu yes
   bindkey "^X^M" complete-first
   

9. A function to make adding flags or prefixing arguments easier:

   # Move to where the arguments belong.
   after-first-word() {
     zle beginning-of-line
     zle forward-word
   }
   zle -N after-first-word
   bindkey "^X1" after-first-word
   

10. Complete with words in the history (like Emacs dabbrev):

    # Complete in history with M-/, M-,
    zstyle ':completion:history-words:*' list no 
    zstyle ':completion:history-words:*' menu yes
    zstyle ':completion:history-words:*' remove-all-dups yes
    bindkey "\e/" _history-complete-older
    bindkey "\e," _history-complete-newer
    

    Of course, all things are mentioned in the comprehensive manual, or the great User’s Guide to the Z-Shell which I wholeheartedly recommend. But one needs to find them. :)

    NP: Aimee Mann—Freeway