How to use arguments from previous command?

Question

I know that Esc + . gives you the last argument of the last command.

But I\'m interested in first argument of the last command. Is there a key

Answer 1

Basically it has a use in yanking previous (command's) arguments.

For instance, if the following command is issued:

echo Hello, world how are you today?

then, Hello, will be the first argument, and today? the sixth, that is the last one; meaning it can be referenced by typing:

Alt+6 followed by Ctrl-Alt-6

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Ctrl is traditionally denoted as a hat character ^ prepended to keys names, and Alt as M- that is Meta prefix.

So the above shortcut can be redefined as ^My to yank.

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Also, there is hats substitution shortcut in the command line:

echo Hello, world!

^Hello^Bye

Bye, world!

to substitute the previous command's first matched string, meaning:

Hello, world! Hello, people!

^Hello^Bye

would result in:

Bye, world! Hello, people!

leaving the second match (hello) unchanged.

Note: Do not leave space between hats, or the operation won't work.

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The above is just a shortcut for:

!:s/Hello/Bye

event-level(*) substitution for the first found (matched) string in the previous command, while prefixing the first part with the g switch will apply to the whole line globally:

echo Hello, world! Hello, people!

!:gs/Hello/Bye

Bye, world! Bye, people!

as usually being done in other related commands such as sed, vi, and in regex (regular expression) - a standart way to search (match string).

No, you can't do !:sg/Hello/Bye or !:s/Hello/Bye/g here, that's the syntax!

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• ! is for events; event might be understood as command output or operation done in the commands history.

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That's what I understood by using it myself and trying things on my own from what I read from various sources including manual pages, blogs, and forums.

Hope it will shed some light into mysterious ways of bash, the Bourne-Again shell (a play on sh shell, which itself is called Bourne shell after its inventor's last name), what is default shell in many distributions including servers (server OS's).

Answer 2

!^ may be the command for the first argument. i'm not sure if there is a way to get the nth.

Answer 3

To use the first argument, you can use !^ or !:1

Example:

$ echo a b c d e 
a b c d e
$ echo !^
echo a
a

$ echo a b c d e 
a b c d e
$ echo !:1
echo a
a

Since your question is about using any other arguments, here are some useful ones:

!^      first argument
!$      last argument
!*      all arguments
!:2     second argument

!:2-3   second to third arguments
!:2-$   second to last arguments
!:2*    second to last arguments
!:2-    second to next to last arguments

!:0     the command
!!      repeat the previous line

The first four forms are more often used. The form !:2- is somewhat counter-intuitive, as it doesn't include the last argument.

Answer 4

Just as M-. (meta-dot or esc-dot or alt-dot) is the readline function yank-last-arg, M-C-y (meta-control-y or esc-ctrl-y or ctrl-alt-y) is the readline function yank-nth-arg. Without specifying n, it yanks the first argument of the previous command.

To specify an argument, press Escape and a number or hold Alt and press a number. You can do Alt--to begin specifying a negative number then release Alt and press the digit (this will count from the end of the list of arguments.

Example:

Enter the following command

$ echo a b c d e f g
a b c d e f g

Now at the next prompt, type echo (with a following space), then

Press Alt-Ctrl-y and you'll now see:

$ echo a

without pressing Enter yet, do the following

Press Alt-3 Alt-Ctrl-y

Press Alt-- 2 Alt-Ctrl-y

Now you will see:

$ echo ace

By the way, you could have put the echo on the line by selecting argument 0:

Press Alt-0 Alt-Ctrl-y

Edit:

To answer the question you added to your original:

You can press Alt-0 then repeatedly press Alt-. to step through the previous commands (arg 0). Similarly Alt-- then repeating Alt-. would allow you to step through the previous next-to-last arguments.

If there is no appropriate argument on a particular line in history, the bell will be rung.

If there is a particular combination you use frequently, you can define a macro so one keystroke will perform it. This example will recall the second argument from previous commands by pressing Alt-Shift-Y. You could choose any available keystroke you prefer instead of this one. You can press it repeatedly to step through previous ones.

To try it out, enter the macro at a Bash prompt:

bind '"\eY": "\e2\e."'

To make it persistent, add this line to your ~/.inputrc file:

"\eY": "\e2\e."

Unfortunately, this doesn't seem to work for arg 0 or negative argument numbers.

Answer 5

I liked @larsmans answer so much I had to learn more. Adding this answer to help others find the man page section and know what to google for:

$ man  -P 'less -p ^HISTORY\ EXPANSION' bash
<...>
Word Designators

Word designators are used to select desired words from the event.
A : separates the event specification from the word designator.
It may be omitted if the word designator begins with a ^, $, *, -,
or %.  Words are numbered from the beginning of the line, with the
first word being denoted by 0 (zero).  Words are inserted into the
current line separated by single spaces.

   0 (zero)
          The zeroth word.  For the shell, this is the command word.
   n      The nth word.
   ^      The first argument.  That is, word 1.
   $      The last argument.
   %      The word matched by the most recent ‘?string?’ search.
   x-y    A range of words; ‘-y’ abbreviates ‘0-y’.
   *      All of the words but the zeroth.
          This is a synonym for ‘1-$’.  
          It is not an error to use * if there is just one word in
          the event; the empty string is returned in that case.
   x*     Abbreviates x-$.
   x-     Abbreviates x-$ like x*, but omits the last word.

   If a word designator is supplied without an event
   specification, the previous command is used as the event.