Basics

tldr cd

  cd

  Change the current working directory.
  More information: https://manned.org/cd.

  - Go to the specified directory:
    cd path/to/directory

  - Go up to the parent of the current directory:
    cd ..

  - Go to the home directory of the current user:
    cd

  - Go to the home directory of the specified user:
    cd ~username

  - Go to the previously chosen directory:
    cd -

  - Go to the root directory:
    cd /

# search by keyword
apropos 'rebase'
git-rebase (1)       - Reapply commits on top of another base tip

# same search with man -k
man -k 'rebase'
git-rebase (1)       - Reapply commits on top of another base tip

man export
No manual entry for export

# search with help
$ help export
export: export [-fn] [name[=value] ...] or export -p
    Set export attribute for shell variables.
    
    Marks each NAME for automatic export to the environment of subsequently
    executed commands.  If VALUE is supplied, assign VALUE before exporting.
    ...

info ls

type ls
ls is aliased to `ls --color=auto'

HIER(7)                                       Linux Programmer's Manual                                       HIER(7)

NAME
       hier - description of the filesystem hierarchy

DESCRIPTION
       A typical Linux system has, among others, the following directories:

       /      This is the root directory.  This is where the whole tree starts.

       /bin   This  directory contains executable programs which are needed in single user mode and to bring the sys‐
              tem up or repair it.
       ...

ls [OPTION]... [FILE]...
ll # list long
la # list all except . and ..
l  # list in columns
-1 # one entry per line
-a # all files, incl hidden
-d # current dir own metadata
-F # classify 
-h # human readable byte size
-i # inodes
-l # long (all metadata)
-o # no group info
-r # reverse order
-R # recursive list
-t # list by time file was modified

# common usage to see oldest modified object
ls -ltra

~$ pushd /var/log
/var/log ~

/var/log$ pushd /dev/
/dev /var/log ~

/dev$ pushd /etc/
/etc /dev /var/log ~

/etc$ popd
/dev /var/log ~

/dev$ popd
/var/log ~

/var/log$ popd
~

~$ 

# view all history
history

# view previous 10 commands
history 10

# grep history
history | grep less

# execute a command from history
!<history-number>
!98

# execute command relative to current history
!-2

# execute last command
!!

# execute last command with sudo
sudo !!
# example:
cat /etc/shadow
cat: /etc/shadow: Permission denied

sudo !!
sudo cat /etc/shadow
...

# replace incorrect string in previous command
cat /etc/shosst
cat: /etc/shosst: No such file or directory
# ^incorrect^corrected^
^shosst^hosts^
cat /etc/hosts
127.0.0.1 localhost
...

# word designator - access arg from prev command
less .profile 
# - replace less with cat
cat !!:1
cat .profile
# ~/.profile: executed by the command interpreter for login shells.
...

# word designator - get all args from previous command
!!:1*
!!:*

# forward search
/ # start search - enter pattern
n # go to next match (forwards)
N # go to previous match (backwards)


# backward search
? # start search - enter pattern
n # go to next match (backwards)
N # go to previous match (forwards)

f # forward one window
b # backward one window
d # forward 1/2 window
u # backward 1/2 window

j # forward one line
10j # forward 10 lines
k # backward one line
10k # backward 10 lines

G # end of file
g # start of file
q or ZZ # exit

F # waiting for data mode (file is being written to)

v # use default editor to edit
h # help
&<pattern> # display only pattern matches

# mark file and return to it
m<letter> # mark a line in a file - ex: ma
'<letter> # go back to the mark - ex: 'a