kugarocks

Commands-1

MAN

This command can view different sections of the manual pages.

man man
man - an interface to the system reference manuals

The table below shows the section numbers of the manual followed by the types of pages they contain.

1 Executable programs or shell commands
2 System calls (functions provided by the kernel)
3 Library calls (functions within program libraries)
4 Special files (usually found in /dev)
5 File formats and conventions, e.g. /etc/passwd
6 Games
7 Miscellaneous (including macro packages and conventions), e.g. man(7), groff(7)
8 System administration commands (usually only for root)
9 Kernel routines [Non standard]

Section

man 1 ls/cp/mv
man 2 write/open/close
man 3 printf/malloc/free
man 4 tty/null/random
man 5 passwd/fstab
man 7 man
man 8 ifconfig/iptables/mount
man 9 fork # not work

Games

fortune can randomly display quotes and jokes.

apt install fortune/fortune-mod/fortunes-zh
man 6 fortune
fortune - print a random, hopefully interesting, adage

Can be combined with cowsay and lolcat to play.

fortune | cowsay | lolcat

PWD

Print Working Directory.

man pwd
pwd - print name of current/working directory

CAT

man cat
cat - concatenate files and print on the standard output

Line No. With Blank Lines

cat -n FILE

Line No. Without Blank

cat -b FILE

LS

man ls
ls - list directory contents

File Details

ls -lh
drwx------ 9 root root 4.0K   Aug  7 22:38 root
crw-rw-rw- 1 root tty  5,   0 Aug  7 22:33 /dev/tty
brw-rw---- 1 root disk 252, 0 Aug  7 21:30 /dev/vda
  • File type: d directory, - file, l link, c character device, b block device.
  • File permissions: 700, Owner: 7, Group: 0, Other: 0
  • Hard link count: 9
  • File owner: root
  • File group: root
  • File size: 4.0K
  • Modification time: Aug 7 22:38
  • File name: root
  • Major device number: 5/252, identifies the device driver
  • Minor device number: 0, identifies a specific device instance within the same class of devices

Only Dirs

ls -ld */

Including hidden files

ls -ld .*/ */

Specify Dir

ls -ld /usr

Type Symbols

ls -lF /
  • /: directory
  • *: executable file
  • @: symbolic link
  • |: named pipe
  • =: socket

Hidden Characters

ls ~ | wc -l

There are hidden characters \n in the output of the ls command.

ls ~ | od -c
0000000   f   i   l   e  \n   f   o   o  \n   f   o   o   b   a   r  \n
0000020

You can also use cat -A.

ls ~ | cat -A
file$
foo$
foobar$

FILE

Show file type

man file
file — determine file type

Character/Block Device

file /dev/tty
/dev/tty: character special (5/0)
file /dev/vda
/dev/vda: block special (252/0)

Note the trailing slash.

file /bin
/bin: symbolic link to usr/bin
file /bin/
/bin/: directory

LESS

The more command can only load by pressing Enter, the less command is more powerful because less is more.

man less
less - opposite of more

USERMOD

man usermod
usermod - modify a user account

Disable Account Login

usermod -s /sbin/nologin kuga

This command will change bin/sh to /sbin/nologin in /etc/passwd

kuga:x:1000:1000::/home/kuga:/sbin/nologin

Grant User Group

The following command will grant the kuga user the sudo user group.

usermod -aG sudo kuga

LN

man ln
ln - make links between files

go rocks

DF

man df
df - report file system disk space usage

Readable Format

df -h

Specify File System Type

df -h -t ext4
df -h -t apfs

ext4 is the file system type of Linux, apfs is the file system type of macOS.

DU

Disk Usage

man du
du - estimate file space usage

Total Size of Dir

du -sh ~/Downloads

Sort Files - Including Subdirs

du -ah ~/Downloads/* | sort -rh | head -n 5
du -ah ~/Downloads --max-depth=1 | sort -rh | head -n 10

Sort Files - Excluding Subdirs

du -sh ~/Downloads/* | sort -rh | head -n 5
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