man and history commands

man

1. The Structure of Man Pages (Sections)

Linux manuals are divided into numbered categories:

Section Content Type Example

1 User Commands ls, pwd, grep

5 File Formats /etc/passwd, /etc/fstab

8 System Admin Commands fdisk, reboot, iptables

How to use it: To see the configuration file format for passwords instead of the command, you would run:

man 5 passwd

2. Searching for Commands

man -k (Keyword Search)

This searches the short descriptions of every man page for a specific keyword. It is identical to the apropos command.

• Example: man -k partition, man -k network

3. Navigating inside a Man Page

Since man uses the less pager by default, you need to know these keyboard shortcuts:

• /pattern: Search forward for "pattern".

• ?pattern: Search backward for "pattern".

• n / N: Go to the next or previous match.

• g / G: Go to the top (start) or bottom (end) of the page.

• q: Quit the manual.

4. Location and Path

Where these manual files are stored or how the system finds them.

• Location: Usually /usr/share/man.

• -w: Show the where (the path to the actual manual file on disk).

history

It executes the command number 9 of the history list of commands.

$ history

$ !9

Executes the last command you used:

$ !!

This represents only the very last word (argument) of the previous command:

$ !$

• Example:

  $ mkdir /var/www/html/my_project

  $ cd !$ # This expands to: cd /var/www/html/my_project

Comparison

Shortcut Name What it captures Best for...

!! Bang Bang The whole line Adding sudo or redirecting output (!! > file).

!$ Last Argument The last word Moving, editing, or deleting a file you just touched.

Some flags explained

Writes the history of your current session:

$ history -w

Clears history:

$ history -c

Delete the offset, being the number you have in your history for a command:

$ history -d offset

Append history lines from this session to .bash_history:

$ history -a

Synchronize the history lines from several virtual terminals:

$ history -n

If you manually edited the .bash_history file:

$ history -r

Display that line of the history (without executing it):

$ history -p \!28

Display a range of lines from the history:

$ history -p \!2{5..8}

Search the most recent command that starts with "ls" and show the first argument:

$ history -p \!ls:1

Write anything in the history file:

$ history -s Hello