Manipulating the History of Commands | Unix | ECE 250 | Electrical and Computer Engineering

We have seen how history, !!, !$, and !n can be used to access historical commands or portions thereof. It is, however, also possible to both access and modify the arguments and the command itself of previously issued commands.

Table 1 summarizes the many ways in which entire commands or portions thereof can be referred to in subsequent commands.

Table 1. A summary of referencing previous commands.

	Refer to the..	Refer to the selected argument(s) of the..	Prepend `pre` and append `end` to the..	Prepend `pre` and append `end` to the selected argument(s) of the..
..last command	`!!`	`!:mod`	`pre!!end`	`pre!{:mod}end`
..`n`th command	`!n`	`!n:mod`	`pre!{n}end`	`pre!{n:mod}end`
..`n`th most recent command	`!-n`	`!-n:mod`	`pre!{-n}end`	`pre!{-n:mod}end`
..last command starting with `str`	`!str`	`!str:mod`	`pre!{str}end`	`pre!{str:mod}end`
..last command starting containing `trin`	`!?trin?`	`!?trin?:mod`	`pre!{?trin?}end`	`pre!{?trin?:mod}end`

Table 2 shows the allowable modifiers (mod) which may be used to select the specific arguments.

Table 2. A summary of command argument selectors.

`:0`	the command
`:n`	the `n`th argument
`^`	the first argument^*
`$`	the last argument^*
`:m-n`	the `m`th through `n` arguments
`-n`	the same as `-n`^*
`:m-`	the `m`th argument through to the second-to-last argument
*`:m`**	the `m`th argument through to the last argument^*
*``**	all the arguments (the same as `^-$`)^*

^*Note: the colon : can still be used in these case.