Shell Programming (i)

One of the basic features of bash:

Command history: The shell process saves commands that were previously executed by the user in its session;

~]# history

The ability to customize the history can be achieved through environment variables:

The number of commands history that the Histsize:shell process can retain;

Histfile: A file that persists command history;

. bash_history

Histfilesize: The size of the command history file;

Command usage:

History [-c] [-D offset] [n]

or HISTORY-ANRW [filename]

or history-ps parameter [parameters ...]

-C: Clears the command history;

-D Offset: Delete the specified command history

-R: Reads the command history from the file to the history list;

-W: Appends the commands in the history list to the history file;

History #: Displays the most recent # command;

To invoke a command in the command history list:

!#: Once again execute the # command in the history list;

!! : To execute the last command once more;

! String: Executes the most recent command in the command history list that starts with a string;

Note: Repeated executions of commands sometimes need to depend on idempotent;

Call the last parameter of the previous command:

Shortcut key: ESC,.

String:!$

Control the way the command history is logged:

Environment variable: Histcontrol

Ignoredups: Ignore duplicate commands;

Ignorespace: Ignores commands that begin with whitespace characters;

Ignoreboth: Both are effective at the same time;

To modify the value of a variable:

Name= ' VALUE '

Shell Programming (i)