Bash – How to Access the Second Argument from the Last Command in History

bashcommand historycommand linehistory-expansion

I am starting to learn some Regex, therefore I use this command repeatedly:

grep pattern /usr/share/dict/american-english

Only the part with pattern changes, so I have to write the long expression "/usr/share/dict/american-english" again and again.

Someone made the remark that it is possible to expand an argument of a command from the command history by typing cryptic character combinations instead of the full expression.
Could you tell me those cryptic character combinations ?

Best Answer

You can use <M-.> (or <Esc>. if your Meta key is being used for something else), that is, Meta-dot (or <esc> dot), where Meta is usually the Alt key, to recall the last argument of the previous command. So, first you would type

$ grep foo /usr/share/dict/american-english

And then if you wanted to grep for something else, you would type

$ grep bar

After typing a space and then Esc. (that is, first pressing the escape key, and then the period key):

$ grep bar /usr/share/dict/american-english

You can also use either of the following:

$ grep bar !:2
$ grep bar !$

Where !:2 and !$ mean "second argument" and "last argument" respectively.

Related Solutions

Number of Backslashes Needed for Escaping Regex Backslash on Command-Line

For the unquoted example, each \\ pair passes one backslash to grep, so 4 backslashes pass two to grep, which translates to a single backslash. 6 backslashes pass three to grep, translating to one backslash and one \c, which is equal to c. One additional backslash does not change anything, because it is translated \c -> c by the shell. Eight backslashes in the shell are four in grep, translated to two, so this does not match anymore.

For the example in double quotes, note what follows your second quote from the bash manpage:

The backslash retains its special meaning only when followed by one of the following characters: $, `, ", \, or newline.

I.e. when you give an odd number of backslashes, the sequence ends in \c, which would be equal to c in the unquoted case, but when quoted, the backslash looses its special meaning, so \c is passed to grep. That is why the range of "possible" backslashes (i.e. those that make up a pattern matching your example file) slides down by one.

Command History – How to Get Command Name of the Last Executed Command

You can select particular word from last typed command with !!: and a word designator. As a word designator you need 0. You may find ^ and $ useful too. From man bash:

Word Designators

0 (zero) The zeroth word. For the shell, this is the command word.

^ The first argument. That is, word 1.

$ The last argument.

So in your case try:

echo !!:0

Best Answer

Related Solutions

Number of Backslashes Needed for Escaping Regex Backslash on Command-Line

Command History – How to Get Command Name of the Last Executed Command

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