I. Monitoring Programs

Peeking at the processes

$ ps

$ ps -ef 
// -e: show all processes
// -f: display a full format lsiting

$ ps -ef | grep $PID

Real-time process monitoring

$ top

• First Line: Shows the current time, how long the system has been up, the number of users logged in, and the load average on the system
  • The load average appears as three numbers: 1-minutes, 5-minutes, 15-minutes
• Second Line: Tasks, how many processes are running, sleeping, stopped, and zombie
• Next Lines: Show CPU usages, status of system memory

Stopping processes

$ kill 

• kill -1 PID: hangs up
• kill -3 PID: stops running
• kill -9 PID: unconditionally terminates

II.Monitoring Disk Space

df

To see how much disk space is available on an individual device

$ df
$ df -h

du

Shows the disk usage for a specific directory(by default is current directory)

$ du
$ du -sh
$ du -sh $FOLDER_NAME
$ du -ch // show total

III. Processing Data Files

Sort for data

use sort command

$ cat file1
one
two
three
four
five
$ sort file1
five
four
one
three
two
$
$ cat file2
1
2
100
45
3
10
145
75
$ sort file2
1
10
100
145
2
3
45
75
$
$ sort -n file2 // -n to sort numbers
1
2
3
10
45
75
100
145

Searching for data

grep [options] pattern [file]

• grep example

$ grep three file1
three
$ grep t file1
two
three

• Reverse grep, output lines that don’t match the pattern

$ grep -v t file1
one
four
five

• Find the line number where matching patterns are found

$ grep -n t file1
2:two
3:three

• Count of how many lines contain the matching pattern

$ grep -c t file1
2

• Specify more than one mathing pattern

$ grep -e t -e f file1
two
three
four
five

• Use regular expression

$ grep [tf] file1
two
three
four
five

Compressing Data

Archiving data