1. stdin,
stdout
pup, Go & life at the command-line

3. stdin,
stdout
pup, Go & life at the command-line

5. $ cd ~/talks/codementor
$ cat hello.txt
Hello, Code Mentor!
$

8. CLI life: Data

20. data

21. [LOG] some data
[LOG] more data
[LOG] even more

22. col1,col2,col3
some,data,and
even,more,data

23. {
“some”: “data”,
“more”: “data”
}

24. <div>
<h1>Some</h1>
<p>data</p>
</div>

26. grep & nl

36. cat grep

37. cat grep

42. pipes!

43. $ cat Shakespeare.txt |
sed -e 's/s+/n/g' |
tr -d ' ' |
grep -e '^$' -v |
tr '[:upper:]' '[:lower:]' |
sort | uniq -c | sort -nr |
head -n 50

44. $ cat Shakespeare.txt |
sed -e 's/s+/n/g' |
tr -d ' ' |
grep -e '^$' -v |
tr '[:upper:]' '[:lower:]' |
sort | uniq -c | sort -nr |
head -n 50

45. $ cat Shakespeare.txt |
sed -e 's/s+/n/g' |
tr -d ' ' |
grep -e '^$' -v |
tr '[:upper:]' '[:lower:]' |
sort | uniq -c | sort -nr |
head -n 50

46. $ cat Shakespeare.txt |
sed -e 's/s+/n/g' |
tr -d ' ' |
grep -e '^$' -v |
tr '[:upper:]' '[:lower:]' |
sort | uniq -c | sort -nr |
head -n 50

47. $ cat Shakespeare.txt |
sed -e 's/s+/n/g' |
tr -d ' ' |
grep -e '^$' -v |
tr '[:upper:]' '[:lower:]' |
sort | uniq -c | sort -nr |
head -n 50

48. $ cat Shakespeare.txt |
sed -e 's/s+/n/g' |
tr -d ' ' |
grep -e '^$' -v |
tr '[:upper:]' '[:lower:]' |
sort | uniq -c | sort -nr |
head -n 50

49. $ cat Shakespeare.txt |
sed -e 's/s+/n/g' |
tr -d ' ' |
grep -e '^$' -v |
tr '[:upper:]' '[:lower:]' |
sort | uniq -c | sort -nr |
head -n 50

50. $ cat Shakespeare.txt |
sed -e 's/s+/n/g' |
tr -d ' ' |
grep -e '^$' -v |
tr '[:upper:]' '[:lower:]' |
sort | uniq -c | sort -nr |
head -n 50

51. $ cat Shakespeare.txt |
sed -e 's/s+/n/g' |
tr -d ' ' |
grep -e '^$' -v |
tr '[:upper:]' '[:lower:]' |
sort | uniq -c | sort -nr |
head -n 50

53. $ cat Shakespeare.txt |
sed -e 's/s+/n/g' |
tr -d ' ' |
grep -e '^$' -v |
tr '[:upper:]' '[:lower:]' |
sort | uniq -c | sort -nr |
head -n 50

54. curl & wget

55. $ wget -O Shakespeare.txt
http://gutenberg.org/cache/epub/100/pg100.txt

56. $ wget -O Shakespeare.txt
http://gutenberg.org/cache/epub/100/pg100.txt

57. $ wget -O Shakespeare.txt
http://gutenberg.org/cache/epub/100/pg100.txt

58. wget =

59. $ wget --load-cookies cookies.txt

63. $ wget -O Shakespeare.txt
http://gutenberg.org/cache/epub/100/pg100.txt

64. $ curl -o Shakespeare.txt
http://gutenberg.org/cache/epub/100/pg100.txt

65. $ cat Shakespeare.txt |
sed -e 's/s+/n/g' |
tr -d ' ' |
grep -e '^$' -v |
tr '[:upper:]' '[:lower:]' |
sort | uniq -c | sort -nr |
head -n 50

66. $ curl http://gutenberg.org... |
sed -e 's/s+/n/g' |
tr -d ' ' |
grep -e '^$' -v |
tr '[:upper:]' '[:lower:]' |
sort | uniq -c | sort -nr |
head -n 50

67. curl &
wget

68. curl &
wget

70. I hate HTML

71. HTML is
really hard

73. “Every time you attempt to
parse HTML with regular
expressions, the unholy child
weeps the blood of virgins,
and Russian hackers pwn
your webapp.”

74. “Have you tried using an
XML parser instead?”

75. But it gets
worse

76. <tbody>
<tr><img src="foo"></tr>
<tr><img/><br>
</tbody>
</table>

77. Yes, this is valid HTML:
<tbody>
<tr><img src="foo"></tr>
<tr><img/><br>
</tbody>
</table>

78. Yes, this is valid HTML:
<tbody>
<tr><img src="foo"></tr>
<tr><img/><br>
</tbody>
</table>

79. Yes, this is valid HTML:
<tbody>
<tr><img src="foo"></tr>
<tr><img/><br>
</tbody>
</table>

80. Yes, this is valid HTML:
<tbody>
<tr><img src="foo"></tr>
<tr><img/><br>
</tbody>
</table>

83. NEVER TRY
TO WRITE AN
HTML PARSER

84. Nokogiri 鋸

87. pup

107. Still HTML

111. $ curl -L -s reddit.com/r/programming/ |
pup p.title a[href^=http] attr{href}
$ curl -s https://news.ycombinator.com/ |
pup td.title a[href^=http] attr{href}

112. $ curl -L -s reddit.com/r/programming/ |
pup p.title a[href^=http] attr{href}
$ curl -s https://news.ycombinator.com/ |
pup td.title a[href^=http] attr{href}

113. $ curl -L -s reddit.com/r/programming/ |
pup p.title a[href^=http] attr{href}
$ curl -s https://news.ycombinator.com/ |
pup td.title a[href^=http] attr{href}

114. $ curl -L -s reddit.com/r/programming/ |
pup p.title a[href^=http] attr{href}
$ curl -s https://news.ycombinator.com/ |
pup td.title a[href^=http] attr{href}

115. $ curl -s https://news.ycombinator.com/ |
pup td.title a[href^=http] json{}
[
{
"attrs": {
"href": "https://hacks.mozilla.org/2014/10/passwordless-authentication-
secure-simple-and-fast-to-deploy/"
},
...
]

116. $ curl -s https://news.ycombinator.com/ |
pup td.title a[href^=http] json{}
[
{
"attrs": {
"href": "https://hacks.mozilla.org/2014/10/passwordless-authentication-
secure-simple-and-fast-to-deploy/"
},
...
]

117. $ curl -s https://news.ycombinator.com/ |
pup td.title a[href^=http] json{}
[
{
"attrs": {
"href": "https:.../"
},
"tag": "a",
"text": "SHOW HN: pup"
},
...
]

118. github.com/EricChiang/pup

119. Part II:
Building CLI
tools in Go

120. import java.util.Scanner;
class Hello {
public static void main(String[] args) {
Scanner reader = new Scanner(System.in);
System.out.print("Enter your name: ");
String name = reader.nextLine();
System.out.printf("Hello, "+name+"!");
}
}

122. import java.util.Scanner;
class Hello {
public static void main(String[] args) {
Scanner reader = new Scanner(System.in);
System.out.print("Enter your name: ");
String name = reader.nextLine();
System.out.printf("Hello, "+name+"!");
}
}

123. import java.util.Scanner;
class Hello {
public static void main(String[] args) {
Scanner reader = new Scanner(System.in);
System.out.print("Enter your name: ");
String name = reader.nextLine();
System.out.printf("Hello, "+name+"!");
}
}

125. import java.util.Scanner;
class Hello {
public static void main(String[] args) {
Scanner reader = new Scanner(System.in);
System.out.print("Enter your name: ");
String name = reader.nextLine();
System.out.printf("Hello, "+name+"!");
}
}

128. Why
Go?

129. Why
not?

130. Taken from Rob Pike’s talk public static void main (2012)

131. “dear god make it stop”
Taken from Rob Pike’s talk public static void main (2012)

132. Why
not?

133. Why
not?

134. I suck at
this -->

136. Go

137. package main
import "fmt"
func main() {
fmt.Println("Hello, world!")
}

138. line

139. package main
import "io"
import "os"
func main() {
io.Copy(os.Stdout, os.Stdin)
io.WriteString(os.Stdout, "n")
}

140. package main
import "io"
import "os"
func main() {
io.Copy(os.Stdout, os.Stdin)
io.WriteString(os.Stdout, "n")
}

141. package main
import "io"
import "os"
func main() {
io.Copy(os.Stdout, os.Stdin)
io.WriteString(os.Stdout, "n")
}

142. package main
import "io"
import "os"
func main() {
io.Copy(os.Stdout, os.Stdin)
io.WriteString(os.Stdout, "n")
}

143. package main
import "io"
import "os"
func main() {
io.Copy(os.Stdout, os.Stdin)
io.WriteString(os.Stdout, "n")
}

144. $ echo "Hello, World"
Hello, World

145. $ echo "Hello, World"
Hello, World
$ go get github.com/ericchiang/line

146. $ echo "Hello, World"
Hello, World
$ go get github.com/ericchiang/line
$ echo "Hello, World" | line
Hello, World
$

147. url-encode

148. Live demo!

149. gox

151. Messing
with zip

158. Thanks!