Install Scala2017/10/31 |
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Install Scala who runs on Java VM and also provides support for functional programming and a static type system.
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| [1] | It's possible to install from CentOS SCLo Software Collections. |
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# install from SCLo [root@dlp ~]# yum --enablerepo=centos-sclo-rh -y install rh-scala210
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| [2] | Packages from Software Collections are installed uder the /opt directory. To use it, Load environment variables like follows. |
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# load environment variables [root@dlp ~]# scl enable rh-scala210 bash
[root@dlp ~]#
[root@dlp ~]# scala -version Scala code runner version 2.10.6 -- Copyright 2002-2013, LAMP/EPFL which scala /opt/rh/rh-scala210/root/usr/bin/scala |
| [3] | If you'd like to enable 3.5 automatically at login time, configure like follows. |
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[root@dlp ~]#
vi /etc/profile.d/rh-scala210.sh # create new #!/bin/bash source /opt/rh/rh-scala210/enable export X_SCLS="`scl enable rh-scala210 'echo $X_SCLS'`" |
| [4] | Run Scala REPL (Read Eval Print Loop) which is the interactive shell to Test Scala. |
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[root@dlp ~]# scala Welcome to Scala version 2.10.6 (OpenJDK 64-Bit Server VM, Java 1.8.0_151). Type in expressions to have them evaluated. Type :help for more information. # print words scala> println("Hello Scala World") Hello Scala World # set constants scala> val msg:String = "Hello Scala World" msg: String = Hello Scala World scala> println(msg) Hello Scala World # exit scala> sys.exit |
| [5] | Create a sample program to Test Scala. |
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[root@dlp ~]#
vi readfile.scala
import java.io.File
import java.io.FileReader
import java.io.BufferedReader
object readfile {
def main(args: Array[String]) {
val reader = new BufferedReader(new FileReader(new File("/etc/passwd")))
try {
var line : String = null
while ({ line = reader.readLine; line != null }) {
println(line)
}
} finally {
reader.close
}
}
}
# run as a script [root@dlp ~]# scala readfile.scala root:x:0:0:root:/root:/bin/bash bin:x:1:1:bin:/bin:/sbin/nologin daemon:x:2:2:daemon:/sbin:/sbin/nologin ..... ..... # compile and run [root@dlp ~]# scalac readfile.scala [root@dlp ~]# total 16 -rw-------. 1 root root 1441 Dec 19 2016 anaconda-ks.cfg -rw-r--r--. 1 root root 574 Nov 1 19:44 readfile.class -rw-r--r--. 1 root root 1104 Nov 1 19:44 readfile$.class -rw-r--r--. 1 root root 387 Nov 1 19:42 readfile.scala[root@dlp ~]# scala readfile root:x:0:0:root:/root:/bin/bash bin:x:1:1:bin:/bin:/sbin/nologin daemon:x:2:2:daemon:/sbin:/sbin/nologin ..... ..... |