1 /sbin/shutdown
      1 /usr/bin/zsh
      1 /usr/sbin/nologin
[cs50@flume ~/demo]$ cut -d : -f 7 /etc/passwd | sort | uniq -c | sort -n
      1 /bin/sync
      1 /bin/zsh
      1 /sbin/halt
      1 /sbin/shutdown
      1 /usr/bin/zsh
      1 /usr/sbin/nologin
      2 /bin/sh
      3 
      4 /bin/false
     11 /bin/csh
     86 /sbin/nologin
    105 /bin/tcsh
    890 /bin/bash
[cs50@flume ~/demo]$ cut -d : -f 7 /etc/passwd | sort | uniq -c | sort -nr
    890 /bin/bash
    105 /bin/tcsh
     86 /sbin/nologin
     11 /bin/csh
      4 /bin/false
      3 
      2 /bin/sh
      1 /usr/sbin/nologin
      1 /usr/bin/zsh
      1 /sbin/shutdown
      1 /sbin/halt
      1 /bin/zsh
      1 /bin/sync
[cs50@flume ~/demo]$ cut -d : -f 7 /etc/passwd | sort | uniq -c | sort -nr | head -5
    890 /bin/bash
    105 /bin/tcsh
     86 /sbin/nologin
     11 /bin/csh
      4 /bin/false
[cs50@flume ~/demo]$ clear

[cs50@flume ~/demo]$ BB=~cs50/public_html/Lectures/03/Billboard2016-hot100.txt
[cs50@flume ~/demo]$ less $BB
[cs50@flume ~/demo]$ cut -d : -f 3 $BB | less
[cs50@flume ~/demo]$ cut -d : -f 3 $BB | wc -l
100
[cs50@flume ~/demo]$ sort -nr $BB
100:PERFECT:One Direction
99:SEE YOU AGAIN:Wiz Khalifa Featuring Charlie Puth
98:TIIMMY TURNER:Desiigner
97:WICKED:Future
96:HUMBLE AND KIND:Tim McGraw
95:ADVENTURE OF A LIFETIME:Coldplay
94:STARVING:Hailee Steinfeld & Grey Featuring Zedd
93:ALL IN MY HEAD (FLEX):Fifth Harmony Featuring Fetty Wap
92:REALLY REALLY:Kevin Gates
91:CUT IT:O.T. Genasis Featuring Young Dolph
90:NO LIMIT:Usher Featuring Young Thug
89:BACK TO SLEEP:Chris Brown
88:WATCH ME:Silento
87:ALL THE WAY UP:Fat Joe, Rem
86:I KNOW WHAT YOU DID LAST SUMMER:Shawn Mendes & Camila Cabello
85:LEAN ON:Major Lazer & DJ Snake Featuring MO
84:HIDE AWAY:Daya
83:WHEN WE WERE YOUNG:Adele
82:POP STYLE:Drake Featuring The Throne
81:ON MY MIND:Ellie Goulding
80:MIDDLE:DJ Snake Featuring Bipolar Sunshine
79:WILDEST DREAMS:Taylor Swift
78:SIT STILL, LOOK PRETTY:Daya
77:SIDE TO SIDE:Ariana Grande Featuring Nicki Minaj
76:LOST BOY:Ruth B
75:ANTIDOTE:Travis Scott
74:SAY IT:Tory Lanez
73:HYMN FOR THE WEEKEND:Coldplay
72:CAN'T FEEL MY FACE:The Weeknd
71:SORRY:Beyonce
70:LUV:Tory Lanez
69:DOWN IN THE DM:Yo Gotti Featuring Nicki Minaj
68:SUCKER FOR PAIN:Lil Wayne, Wi
67:UNSTEADY:X Ambassadors
66:CLOSE:Nick Jonas Featuring Tove Lo
65:WHITE IVERSON:Post Malone
64:DIE A HAPPY MAN:Thomas Rhett
63:EX'S & OH'S:Elle King
62:ME TOO:Meghan Trainor
61:IN THE NIGHT:The Weeknd
60:NEVER BE LIKE YOU:Flume Featuring Kai
59:FOR FREE:DJ Khaled Featuring Drake
58:STARBOY:The Weeknd Featuring Daft Punk
57:2 PHONES:Kevin Gates
56:HANDS TO MYSELF:Selena Gomez
55:OUI:Jeremih
54:679:Fetty Wap Featuring Remy Boyz
53:EXCHANGE:Bryson Tiller
52:GOLD:Kiiara
51:INTO YOU:Ariana Grande
50:WE DON'T TALK ANYMORE:Charlie Puth Featuring Selena Gomez
49:H.O.L.Y.:Florida Georgia Line
48:DON'T MIND:Kent Jones
47:LET ME LOVE YOU:DJ Snake Featuring Justin Bieber
46:NEVER FORGET YOU:Zara Larsson & MNEK
45:NO:Meghan Trainor
44:LET IT GO:James Bay
43:ONE CALL AWAY:Charlie Puth
42:LIKE I'M GONNA LOSE YOU:Meghan Trainor Featuring John Legend
41:CONTROLLA:Drake
40:SAME OLD LOVE:Selena Gomez
39:HERE:Alessia Cara
38:I HATE U I LOVE U:gnash Featuring Olivia O'Brien
37:JUMPMAN:Drake & Future
36:DANGEROUS WOMAN:Ariana Grande
35:DON'T:Bryson Tiller
34:BROCCOLI:D.R.A.M. Featuring Lil Yachty
33:JUST LIKE FIRE:P!nk
32:THE HILLS:The Weeknd
31:WHAT DO YOU MEAN?:Justin Bieber
30:LOW LIFE:Future Featuring The Weeknd
29:TOO GOOD:Drake Featuring Rihanna
28:TREAT YOU BETTER:Shawn Mendes
27:ROSES:The Chainsmokers Featuring Rozes
26:SEND MY LOVE (TO YOUR NEW LOVER):Adele
25:COLD WATER:Major Lazer Featuring Justin Bieber & MO
24:HOTLINE BLING:Drake
23:STITCHES:Shawn Mendes
22:PILLOWTALK:Zayn
21:HEATHENS:twenty one pilots
20:RIDE:twenty one pilots
19:ME, MYSELF & I:G-Eazy x Bebe Rexha
18:CAKE BY THE OCEAN:DNCE
17:THIS IS WHAT YOU CAME FOR:Calvin Harris Featuring Rihanna
16:WORK FROM HOME:Fifth Harmony Featuring Ty Dolla $ign
15:I TOOK A PILL IN IBIZA:Mike Posner
14:MY HOUSE:Flo Rida
13:NEEDED ME:Rihanna
12:7 YEARS:Lukas Graham
11:CHEAP THRILLS:Sia Featuring Sean Paul
10:CLOSER:The Chainsmokers Featuring Halsey
9:CAN'T STOP THE FEELING!:Justin Timberlake
8:DON'T LET ME DOWN:The Chainsmokers Featuring Daya
7:HELLO:Adele
6:PANDA:Desiigner
5:STRESSED OUT:twenty one pilots
4:WORK:Rihanna Featuring Drake
3:ONE DANCE:Drake Featuring WizKid & Kyla
2:SORRY:Justin Bieber
1:LOVE YOURSELF:Justin Bieber
[cs50@flume ~/demo]$ sort -nr $BB | less
[cs50@flume ~/demo]$ cut -d : -f 2 $BB | grep love
[cs50@flume ~/demo]$ cut -d : -f 2 $BB | head 
LOVE YOURSELF
SORRY
ONE DANCE
WORK
STRESSED OUT
PANDA
HELLO
DON'T LET ME DOWN
CAN'T STOP THE FEELING!
CLOSER
[cs50@flume ~/demo]$ cut -d : -f 2 $BB | grep LOVE
LOVE YOURSELF
SEND MY LOVE (TO YOUR NEW LOVER)
I HATE U I LOVE U
SAME OLD LOVE
LET ME LOVE YOU
[cs50@flume ~/demo]$ cut -d : -f 2 $BB | grep -i love
LOVE YOURSELF
SEND MY LOVE (TO YOUR NEW LOVER)
I HATE U I LOVE U
SAME OLD LOVE
LET ME LOVE YOU
[cs50@flume ~/demo]$ cut -d : -f 3 $BB | sort  |uniq 
Adele
Alessia Cara
Ariana Grande
Ariana Grande Featuring Nicki Minaj
Beyonce
Bryson Tiller
Calvin Harris Featuring Rihanna
Charlie Puth
Charlie Puth Featuring Selena Gomez
Chris Brown
Coldplay
Daya
Desiigner
DJ Khaled Featuring Drake
DJ Snake Featuring Bipolar Sunshine
DJ Snake Featuring Justin Bieber
DNCE
Drake
Drake Featuring Rihanna
Drake Featuring The Throne
Drake Featuring WizKid & Kyla
Drake & Future
D.R.A.M. Featuring Lil Yachty
Elle King
Ellie Goulding
Fat Joe, Rem
Fetty Wap Featuring Remy Boyz
Fifth Harmony Featuring Fetty Wap
Fifth Harmony Featuring Ty Dolla $ign
Flo Rida
Florida Georgia Line
Flume Featuring Kai
Future
Future Featuring The Weeknd
G-Eazy x Bebe Rexha
gnash Featuring Olivia O'Brien
Hailee Steinfeld & Grey Featuring Zedd
James Bay
Jeremih
Justin Bieber
Justin Timberlake
Kent Jones
Kevin Gates
Kiiara
Lil Wayne, Wi
Lukas Graham
Major Lazer & DJ Snake Featuring MO
Major Lazer Featuring Justin Bieber & MO
Meghan Trainor
Meghan Trainor Featuring John Legend
Mike Posner
Nick Jonas Featuring Tove Lo
One Direction
O.T. Genasis Featuring Young Dolph
P!nk
Post Malone
Rihanna
Rihanna Featuring Drake
Ruth B
Selena Gomez
Shawn Mendes
Shawn Mendes & Camila Cabello
Sia Featuring Sean Paul
Silento
Taylor Swift
The Chainsmokers Featuring Daya
The Chainsmokers Featuring Halsey
The Chainsmokers Featuring Rozes
The Weeknd
The Weeknd Featuring Daft Punk
Thomas Rhett
Tim McGraw
Tory Lanez
Travis Scott
twenty one pilots
Usher Featuring Young Thug
Wiz Khalifa Featuring Charlie Puth
X Ambassadors
Yo Gotti Featuring Nicki Minaj
Zara Larsson & MNEK
Zayn
[cs50@flume ~/demo]$ cut -d : -f 3 $BB | sort  |uniq  | wc -l
81
[cs50@flume ~/demo]$ cut -d : -f 3 $BB | sort  |uniq -c | sort -nr
      3 twenty one pilots
      3 The Weeknd
      3 Justin Bieber
      3 Adele
      2 Tory Lanez
      2 Shawn Mendes
      2 Selena Gomez
      2 Meghan Trainor
      2 Kevin Gates
      2 Drake
      2 Desiigner
      2 Daya
      2 Coldplay
      2 Bryson Tiller
      2 Ariana Grande
      1 Zayn
      1 Zara Larsson & MNEK
      1 Yo Gotti Featuring Nicki Minaj
      1 X Ambassadors
      1 Wiz Khalifa Featuring Charlie Puth
      1 Usher Featuring Young Thug
      1 Travis Scott
      1 Tim McGraw
      1 Thomas Rhett
      1 The Weeknd Featuring Daft Punk
      1 The Chainsmokers Featuring Rozes
      1 The Chainsmokers Featuring Halsey
      1 The Chainsmokers Featuring Daya
      1 Taylor Swift
      1 Silento
      1 Sia Featuring Sean Paul
      1 Shawn Mendes & Camila Cabello
      1 Ruth B
      1 Rihanna Featuring Drake
      1 Rihanna
      1 Post Malone
      1 P!nk
      1 O.T. Genasis Featuring Young Dolph
      1 One Direction
      1 Nick Jonas Featuring Tove Lo
      1 Mike Posner
      1 Meghan Trainor Featuring John Legend
      1 Major Lazer Featuring Justin Bieber & MO
      1 Major Lazer & DJ Snake Featuring MO
      1 Lukas Graham
      1 Lil Wayne, Wi
      1 Kiiara
      1 Kent Jones
      1 Justin Timberlake
      1 Jeremih
      1 James Bay
      1 Hailee Steinfeld & Grey Featuring Zedd
      1 gnash Featuring Olivia O'Brien
      1 G-Eazy x Bebe Rexha
      1 Future Featuring The Weeknd
      1 Future
      1 Flume Featuring Kai
      1 Florida Georgia Line
      1 Flo Rida
      1 Fifth Harmony Featuring Ty Dolla $ign
      1 Fifth Harmony Featuring Fetty Wap
      1 Fetty Wap Featuring Remy Boyz
      1 Fat Joe, Rem
      1 Ellie Goulding
      1 Elle King
      1 D.R.A.M. Featuring Lil Yachty
      1 Drake & Future
      1 Drake Featuring WizKid & Kyla
      1 Drake Featuring The Throne
      1 Drake Featuring Rihanna
      1 DNCE
      1 DJ Snake Featuring Justin Bieber
      1 DJ Snake Featuring Bipolar Sunshine
      1 DJ Khaled Featuring Drake
      1 Chris Brown
      1 Charlie Puth Featuring Selena Gomez
      1 Charlie Puth
      1 Calvin Harris Featuring Rihanna
      1 Beyonce
      1 Ariana Grande Featuring Nicki Minaj
      1 Alessia Cara
[cs50@flume ~/demo]$ cut -d : -f 3 $BB | sort  |uniq -c | sort -nr | head
      3 twenty one pilots
      3 The Weeknd
      3 Justin Bieber
      3 Adele
      2 Tory Lanez
      2 Shawn Mendes
      2 Selena Gomez
      2 Meghan Trainor
      2 Kevin Gates
      2 Drake
[cs50@flume ~/demo]$ 
[cs50@flume ~/demo]$ 
[cs50@flume ~/demo]$ 
[cs50@flume ~/demo]$ find ~dfk -name paper.pdf > papers
find: ‘/net/nusers/dfk’: Permission denied
[cs50@flume ~/demo]$ head papers
[cs50@flume ~/demo]$ find ~dfk -name paper.pdf > papers 2> errors
[cs50@flume ~/demo]$ find ~dfk -name paper.pdf 1> papers 2> errors
[cs50@flume ~/demo]$ find ~dfk -name paper.pdf 1> papers 2> /dev/null
[cs50@flume ~/demo]$ ls
errors	harvard.txt  listing  papers  primes  students.txt
[cs50@flume ~/demo]$ ls students.txt 
students.txt
[cs50@flume ~/demo]$ more students.txt 
Michael.T.Aaberg.18@Dartmouth.edu;
Alexander.G.W.Bailey.18@Dartmouth.edu;
Anders.Bando-Hess.19@Dartmouth.edu;
James.W.Beane.III.19@Dartmouth.edu;
Alex.Y.Chan.19@Dartmouth.edu;
Shaket.Chaudhary.19@Dartmouth.edu;
Trevor.J.Colby.19@Dartmouth.edu;
Robert.C.Crawford.19@Dartmouth.edu;
Alexander.J.Danilowicz.19@Dartmouth.edu;
Christopher.O.Davis.18@Dartmouth.edu;
Anthony.F.DiPadova.III.19@Dartmouth.edu;
Anna.E.Dodson.20@Dartmouth.edu;
Jack.W.Elder.18@Dartmouth.edu;
Afnan.Enayet.19@Dartmouth.edu;
Kathryn.E.Flattum.18@Dartmouth.edu;
Shoshana.M.Geller.20@Dartmouth.edu;
Isaac.Gluck.19@Dartmouth.edu;
Alexander.E.Goss.18@Dartmouth.edu;
Joshua.B.Gutow.20@Dartmouth.edu;
Ryan.B.Hall.19@Dartmouth.edu;
Danah.K.Han.20@Dartmouth.edu;
Kazuma.Honjo.UG@Dartmouth.edu;
Kevin.Hu.20@Dartmouth.edu;
Gregory.E.Hunter.18@Dartmouth.edu;
Laya.Indukuri.19@Dartmouth.edu;
Jennifer.Jain.18@Dartmouth.edu;
Clifton.T.Jeffery.19@Dartmouth.edu;
Steven.Jiang.19@Dartmouth.edu;
Liam.S.Jolley.20@Dartmouth.edu;
Wendy.W.Kangethe.19@Dartmouth.edu;
Emma.F.Kennelly.19@Dartmouth.edu;
Chaeyoon.Kim.18@Dartmouth.edu;
Caitlyn.I.Lee.19@Dartmouth.edu;
Qirong.Li.20@Dartmouth.edu;
Stephen.K.Liao.19@Dartmouth.edu;
Tsz.Ki.Lit.19@Dartmouth.edu;
Savannah.M.Liu.18@Dartmouth.edu;
Robert.H.Livaudais.19@Dartmouth.edu;
[cs50@flume ~/demo]$