Know the Physical RAM Size: Linux/Unix

Commands:

1. less /proc/meminfo
2. free -m
3. vmstat -s
4. gnome-system-monitor
5. sudo dmidecode --type memory

find: Make UNIX easy

Description	Command
find a file in a directory	find <directory> -name “<file/dir name>”
case insensitive find	-i (eg: find . -iname '<file/dir name>'
find for regular file types	find . -name '<name>' -type f
find for directories types	find . -name '<name>' -type d
find for symbolic links	find . -name '<name>' -type l
find all empty files in a directory	find . -empty

execute another command on the find results:
Syntax: <find command> -exec <other command> {} \;

grep: Make UNIX easy

Global search for a Regular Expression and Print

Description	Command
Match count	-c
case insensitive search	-i
recursive search	-r
select non-matching lines	-v
show matched text in color	--color
show matched text and next n lines after it	-A n (eg: grep -A 3 "example" demo.txt
show file name along with matched line	-H
exclude hidden directories in search results	--exclude="\.*" (eg: grep -iHr --exclude="\.*" "text" *
show line numbers	-n
search in only specific file types	*.fileType (eg: grep -n "print" *.java)

jar: Make UNIX easy

1. unjar a jar file
jar -xf file.jar

2. List files in jar file, without extracting it
jar -tvf file.jar

3. unzar to a specific directory
unzip file.jar -d destinationDir

vi: Visual Editor: Make UNIX easy

Description	Command
Go to start of file	gg
Go to end of file	G (Shift + g)
Go to start of line	0 (zero)
Go to end of line	$ (dollar)
Highlight similar words	# (Press # with curson on required word)
Go to next line	j
Go to previous line	k
Go to next character	h
Go to previous character	l
Delete current character	x
undo last action	u
redo	Ctrl + u
Delete a line	dd
Delete all lines, from current line to end of the file	dG
Delete all lines, from current line to start of the file	dg
Copy	Use mouse to copy required lines
Paste	Shift + Insert
Refresh the current file	:e (