UNIX for Dummies Questions & Answers

Hi, is there a way in bash--or any other shell--to repeat the preceding argument on the command line? E.g., let's say I want to rename the file "/var/www/conf/httpd.conf" to "/var/www/conf/httpd.conf.bak". I want to be able to type mv /var/www/conf/httpd.conf, and then press a command key that would repeat the preceding argument, so I get mv /var/www/conf/httpd.conf /var/www/conf/httpd.conf, and then I can simply tack on ".bak" on the final argument so generated.
thanks,

I use ksh and vi-mode command line editing. vi-mode command line editing is available on bash too (with set -o vi).

I'd do something similar to the following..... (I'm emphasising the <space>'s here to show what I'm doing....

Code:

mv<space>/var/www/conf/httpd.conf<space>
...then...
<Esc>F<space>ly$$pi.bak

Probably just as easy to retype it

That's...
<Esc> - Enter command mode
F<space> - Go backwards to the first space (before /var)
l - Go right one character
y$ - Yank to end of line
$ - Go to end of line
p - Paste
i - insert

Then, we're back in editing mode to add .bak

All done

Might be an easier way with bash....?

Cheers
ZB

I use emacs mode with ksh and bash. In either shell, I can use the sequence <escape> <dot> to represent the last argument on the previous command. But this only works in emacs mode.
set -o emacs

I do a similar thing in tcsh with !$ to repeat the last argument of the previous command.

For the previous argument of the current command, there is no easy way that I see of doing this.... the quickest route would probably be....

Code:

x=/var/www/conf/httpd.conf
mv $x $x.bak

Cheers
ZB

I missed that the OP wanted to repeat the last arg on the current line. I'll confess that I use a somewhat lame trick in a case like that...

echo some-really-long-argument
cp <escape><dot> <escape><dot>.old

I found out that there is currently no readline function (bash uses the readline library for command line editing) to repeat the previous argument. However, I did solve the problem:

As a general solution, for any shell that supports brace expansion, you can use this trick (note that csh, tcsh, bash and pdksh support brace expansion, whereas sh and ksh do not):
mv /var/www/conf/httpd.conf{,.bak}

I.e., the first element in the brace is simply empty. This trick does what we want, but the arguments will not be visible as two separate arguments on the command line, but will be separated (as mv /var/www/conf/httpd.conf /var/www/conf/httpd.conf.bak) when the command is actually executed.

If you actually want an editing command that will repeat the previous argument on the command line, you have to create a macro.

If you use pdksh in emacs mode, you can put the following line in its ENV config file:
bind -m '^[w=^[b^[^] ^k^y^y'

(Note there are spaces in here.) This creates a macro bound to Meta-w (Alt-w).

If you use bash in emacs mode (or use any other readline-enabled program), then create a file ~/.inputrc, and put the following line there:

Meta-w: "\C-w\C-y\ \C-y"

(Note there is a space b/w two slashes here.) This creates a macro bound to M-w (Alt-w) that cuts/kills the previous non-whitespace string (C-w), and then pastes/yanks (C-y) it two times, putting a space in between. This does just what we want. (If you want to try it out for the current session, before making it permanent in .inputrc, type bind 'Meta-w: "\C-w\C-y\ \C-y"' at the bash command line.)

cheers...

deleted - misread OPs intentions

bakunin