4 ms·

In bash: $_ in a command gets substituted by the last argument of the last command you typed - happens to be useful surprisingly often. Simple example: copy a

by vram22 10y ago

In bash: $_ in a command gets substituted by the last argument of the last command you typed - happens to be useful surprisingly often. Simple example: copy a file to some other directory, then cd or pushd to that directory: $ cp some_file /long/path/to/directory # cd $_ But there are many other cases where I regularly find it useful. _ also evaluates to result of the last expression in the Python interactive shell, and probably in IPython (command-line version) as well - need to confirm it about IPython. Edited for formatting of commands above.

tyrylu 10y ago
Not the original poster, but the _ trick works in ipython as well.
- vram22 10y ago
  Cool, thanks for confirming.
ryandrake 10y ago
Another useful bash thing: !! (which substitutes the last command you entered) cat /really/long/path/to/something/only/readable/by/root cat: Permission denied (goddamnit) sudo !!
- vram22 10y ago
  Yes, that's a good one :) There are zillions more such that can be done in Unix, of course, if one puts one's mind to it and experiments, even without spending a lot of time. Another simple one I use some is to define some environment variables to the value of long directory names to which I need to go often as part of some project. Then I can just do: cd $short_name_for_that_dir A shell alias can also be used instead.
- blacksmith_tb 10y ago
  Oh yeah, I sudo bang-bang all the time (it's in other shells, too, zsh for example). I am also fond of !$, which is the object of your last command - lots of times I will ls a file to see the timestamp or confirm it's there; and then want to open it / edit it / rm it, which just looks like $ ls /long/path/to/file.ext $ less !$
- waterhouse 10y ago
  What if you need to run a third version of the command, or a version that involves deletions, e.g. "less /really/long/path/to/..."? bash-3.2$ less /var/log/authd.log.0.gz "/var/log/authd.log.0.gz" may be a binary file. See it anyway? bash-3.2$ I type: control-P control-A meta-D zcat control-E | SPACE less bash-3.2$ zcat /var/log/authd.log.0.gz | less On the OS X terminal, you have to configure it to treat option as meta before the meta-D above will work. I forget whether common Linux terminals require such configuration. (Edit: zless would work just as well here, and on Linux "less" appears to basically have the functionality of zless.)
  - mwpmaybe 10y ago
    With set -o vi: <ESC> k cw zcat <ESC> A <SPACE> | <SPACE> less <CR> Very natural for any Vi user: go up a "line", change the first word, then append.
- deathanatos 10y ago
  Another one I love is that both bash & zsh can edit the current command in $EDITOR. In bash, it's ^X^E by default, and in zsh, I think you have to bind it. (it's edit-command-line, which I strangely can't find in man zshzle.)
billbrown 10y ago
Instead of $_ you may find ESC+. easier. I have.
- vram22 10y ago
  Cool, didn't know of that one.

by vram22 10y ago

tyrylu 10y ago

Not the original poster, but the _ trick works in ipython as well.

vram22 10y ago
Cool, thanks for confirming.

ryandrake 10y ago

Another useful bash thing: !! (which substitutes the last command you entered) cat /really/long/path/to/something/only/readable/by/root cat: Permission denied (goddamnit) sudo !!

vram22 10y ago
Yes, that's a good one :) There are zillions more such that can be done in Unix, of course, if one puts one's mind to it and experiments, even without spending a lot of time. Another simple one I use some is to define some environment variables to the value of long directory names to which I need to go often as part of some project. Then I can just do: cd $short_name_for_that_dir A shell alias can also be used instead.
blacksmith_tb 10y ago
Oh yeah, I sudo bang-bang all the time (it's in other shells, too, zsh for example). I am also fond of !$, which is the object of your last command - lots of times I will ls a file to see the timestamp or confirm it's there; and then want to open it / edit it / rm it, which just looks like $ ls /long/path/to/file.ext $ less !$
waterhouse 10y ago
What if you need to run a third version of the command, or a version that involves deletions, e.g. "less /really/long/path/to/..."? bash-3.2$ less /var/log/authd.log.0.gz "/var/log/authd.log.0.gz" may be a binary file. See it anyway? bash-3.2$ I type: control-P control-A meta-D zcat control-E | SPACE less bash-3.2$ zcat /var/log/authd.log.0.gz | less On the OS X terminal, you have to configure it to treat option as meta before the meta-D above will work. I forget whether common Linux terminals require such configuration. (Edit: zless would work just as well here, and on Linux "less" appears to basically have the functionality of zless.)
- mwpmaybe 10y ago
  With set -o vi: <ESC> k cw zcat <ESC> A <SPACE> | <SPACE> less <CR> Very natural for any Vi user: go up a "line", change the first word, then append.
deathanatos 10y ago
Another one I love is that both bash & zsh can edit the current command in $EDITOR. In bash, it's ^X^E by default, and in zsh, I think you have to bind it. (it's edit-command-line, which I strangely can't find in man zshzle.)

billbrown 10y ago

Instead of $_ you may find ESC+. easier. I have.

vram22 10y ago
Cool, didn't know of that one.