Posts tagged "event-designators"

How to run commands from your bash history ?

Viewing your bash history is pretty easy. Type history in your shell and you will be presented with the latest 500 or 1000 (depends on distro/bash settings, ) commands you entered.
But what if you want to run one or more commands from the history file, how can that be accomplished ?
Well, the not so effective way is to type history | grep mycommand, then copy and paste in the terminal.

However, if your command expands on multiple lines the above procedure is pretty painful.
Here’s a more efficient way:

Introducing History expansion and the event designators:

The command Description
!! Repeat last command
! Start a history substitution
!n Refers to the command line n
!string Invokes the command starting with “string”
!?string Refers to the most recent command containing “string”
^string1^string2 Repeats the last command and replaces string1 with string2

 Here are a couple of practical examples:

Repeats last command, in this case is whoami.

whoami

From the history file it Invokes the latest command containing hostname.

hostname

String replacement:

 

[root@nyx log]# tail /var/log/messages | head -n 2    #showing first 2 lines from /var/log/messages

Aug 22 19:39:56 euve59329 Plesk/Courier authd[20849]: No such user 'cage@nixware.net' in mail authorization database

Aug 22 20:05:26 euve59329 Plesk/Courier authd[21813]: No such user 'psychoza@nixware.net' in mail authorization database

[root@nyx log]# ^messages^mysqld.log     #from the last command replace messages with mysqld.log and execute the command

tail /var/log/mysqld.log | head -n 2

140822  4:03:28 [ERROR] Invalid (old?) table or database name 'comment _subscribers'

140822  4:03:28 [ERROR] Invalid (old?) table or database name 'mp3-players'

[root@nyx log]#