Console

object Console extends AnsiColor

Implements functionality for printing Scala values on the terminal. For reading values use StdIn. Also defines constants for marking up text on ANSI terminals.

Console Output

Use the print methods to output text.

scala> Console.printf(
  "Today the outside temperature is a balmy %.1f°C. %<.1f°C beats the previous record of %.1f°C.\n",
  -137.0,
  -135.05)
Today the outside temperature is a balmy -137.0°C. -137.0°C beats the previous record of -135.1°C.

ANSI escape codes

Use the ANSI escape codes for colorizing console output either to STDOUT or STDERR.

import Console.{GREEN, RED, RESET, YELLOW_B, UNDERLINED}

object PrimeTest {

  def isPrime(): Unit = {

    val candidate = io.StdIn.readInt().ensuring(_ > 1)

    val prime = (2 to candidate - 1).forall(candidate % _ != 0)

    if (prime)
      Console.println(s"${RESET}${GREEN}yes${RESET}")
    else
      Console.err.println(s"${RESET}${YELLOW_B}${RED}${UNDERLINED}NO!${RESET}")
  }

  def main(args: Array[String]): Unit = isPrime()

}

$ scala PrimeTest

1234567891

yes

$ scala PrimeTest

56474

NO!

IO redefinition

Use IO redefinition to temporarily swap in a different set of input and/or output streams. In this example the stream based method above is wrapped into a function.

import java.io.{ByteArrayOutputStream, StringReader}

object FunctionalPrimeTest {

  def isPrime(candidate: Int): Boolean = {

    val input = new StringReader(s"$candidate\n")
    val outCapture = new ByteArrayOutputStream
    val errCapture = new ByteArrayOutputStream

    Console.withIn(input) {
      Console.withOut(outCapture) {
        Console.withErr(errCapture) {
          PrimeTest.isPrime()
        }
      }
    }

    if (outCapture.toByteArray.nonEmpty) // "yes"
      true
    else if (errCapture.toByteArray.nonEmpty) // "NO!"
      false
    else throw new IllegalArgumentException(candidate.toString)
  }

  def main(args: Array[String]): Unit = {
    val primes = (2 to 50) filter (isPrime)
    println(s"First primes: $primes")
  }

}

$ scala FunctionalPrimeTest

First primes: Vector(2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47)

Source: Console.scala

Linear Supertypes

AnsiColor, AnyRef, Any

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Console
AnsiColor
AnyRef
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Value Members

final def !=(arg0: Any): Boolean
Test two objects for inequality.
Test two objects for inequality.
returns
true if !(this == that), false otherwise.
Definition Classes
AnyRef → Any
final def ##: Int
Equivalent to x.hashCode except for boxed numeric types and null.
Equivalent to x.hashCode except for boxed numeric types and null. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. For null returns a hashcode where null.hashCode throws a NullPointerException.
returns
a hash value consistent with ==
Definition Classes
AnyRef → Any
final def ==(arg0: Any): Boolean
The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).
The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).
returns
true if the receiver object is equivalent to the argument; false otherwise.
Definition Classes
AnyRef → Any
final val BLACK: String("\u001B[30m")
Foreground color for ANSI black
Foreground color for ANSI black
Definition Classes
AnsiColor
final val BLACK_B: String("\u001B[40m")
Background color for ANSI black
Background color for ANSI black
Definition Classes
AnsiColor
final val BLINK: String("\u001B[5m")
ANSI blink
ANSI blink
Definition Classes
AnsiColor
final val BLUE: String("\u001B[34m")
Foreground color for ANSI blue
Foreground color for ANSI blue
Definition Classes
AnsiColor
final val BLUE_B: String("\u001B[44m")
Background color for ANSI blue
Background color for ANSI blue
Definition Classes
AnsiColor
final val BOLD: String("\u001B[1m")
ANSI bold
ANSI bold
Definition Classes
AnsiColor
final val CYAN: String("\u001B[36m")
Foreground color for ANSI cyan
Foreground color for ANSI cyan
Definition Classes
AnsiColor
final val CYAN_B: String("\u001B[46m")
Background color for ANSI cyan
Background color for ANSI cyan
Definition Classes
AnsiColor
final val GREEN: String("\u001B[32m")
Foreground color for ANSI green
Foreground color for ANSI green
Definition Classes
AnsiColor
final val GREEN_B: String("\u001B[42m")
Background color for ANSI green
Background color for ANSI green
Definition Classes
AnsiColor
final val INVISIBLE: String("\u001B[8m")
ANSI invisible
ANSI invisible
Definition Classes
AnsiColor
final val MAGENTA: String("\u001B[35m")
Foreground color for ANSI magenta
Foreground color for ANSI magenta
Definition Classes
AnsiColor
final val MAGENTA_B: String("\u001B[45m")
Background color for ANSI magenta
Background color for ANSI magenta
Definition Classes
AnsiColor
final val RED: String("\u001B[31m")
Foreground color for ANSI red
Foreground color for ANSI red
Definition Classes
AnsiColor
final val RED_B: String("\u001B[41m")
Background color for ANSI red
Background color for ANSI red
Definition Classes
AnsiColor
final val RESET: String("\u001B[0m")
Reset ANSI styles
Reset ANSI styles
Definition Classes
AnsiColor
final val REVERSED: String("\u001B[7m")
ANSI reversed
ANSI reversed
Definition Classes
AnsiColor
final val UNDERLINED: String("\u001B[4m")
ANSI underlines
ANSI underlines
Definition Classes
AnsiColor
final val WHITE: String("\u001B[37m")
Foreground color for ANSI white
Foreground color for ANSI white
Definition Classes
AnsiColor
final val WHITE_B: String("\u001B[47m")
Background color for ANSI white
Background color for ANSI white
Definition Classes
AnsiColor
final val YELLOW: String("\u001B[33m")
Foreground color for ANSI yellow
Foreground color for ANSI yellow
Definition Classes
AnsiColor
final val YELLOW_B: String("\u001B[43m")
Background color for ANSI yellow
Background color for ANSI yellow
Definition Classes
AnsiColor
final def asInstanceOf[T0]: T0
Cast the receiver object to be of type T0.
Cast the receiver object to be of type T0.
Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression 1.asInstanceOf[String] will throw a ClassCastException at runtime, while the expression List(1).asInstanceOf[List[String]] will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.
returns
the receiver object.
Definition Classes
Any
Exceptions thrown
ClassCastException if the receiver object is not an instance of the erasure of type T0.
def clone(): AnyRef
Create a copy of the receiver object.
Create a copy of the receiver object.
The default implementation of the clone method is platform dependent.
returns
a copy of the receiver object.
Attributes
protected[lang]
Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.CloneNotSupportedException]) @native()
Note
not specified by SLS as a member of AnyRef
final def eq(arg0: AnyRef): Boolean
Tests whether the argument (that) is a reference to the receiver object (this).
Tests whether the argument (that) is a reference to the receiver object (this).
The eq method implements an equivalence relation on non-null instances of AnyRef, and has three additional properties:
- It is consistent: for any non-null instances x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.
- For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false.
- null.eq(null) returns true.
When overriding the equals or hashCode methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).
returns
true if the argument is a reference to the receiver object; false otherwise.
Definition Classes
AnyRef
def equals(arg0: AnyRef): Boolean
The equality method for reference types.
The equality method for reference types. Default implementation delegates to eq.
See also equals in scala.Any.
returns
true if the receiver object is equivalent to the argument; false otherwise.
Definition Classes
AnyRef → Any
def err: PrintStream
The default error, can be overridden by withErr
def finalize(): Unit
Called by the garbage collector on the receiver object when there are no more references to the object.
Called by the garbage collector on the receiver object when there are no more references to the object.
The details of when and if the finalize method is invoked, as well as the interaction between finalize and non-local returns and exceptions, are all platform dependent.
Attributes
protected[lang]
Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.Throwable])
Note
not specified by SLS as a member of AnyRef
def flush(): Unit
Flushes the output stream.
Flushes the output stream. This function is required when partial output (i.e. output not terminated by a newline character) has to be made visible on the terminal.
final def getClass(): Class[_ <: AnyRef]
Returns the runtime class representation of the object.
Returns the runtime class representation of the object.
returns
a class object corresponding to the runtime type of the receiver.
Definition Classes
AnyRef → Any
Annotations
@native()
def hashCode(): Int
The hashCode method for reference types.
The hashCode method for reference types. See hashCode in scala.Any.
returns
the hash code value for this object.
Definition Classes
AnyRef → Any
Annotations
@native()
def in: BufferedReader
The default input, can be overridden by withIn
final def isInstanceOf[T0]: Boolean
Test whether the dynamic type of the receiver object is T0.
Test whether the dynamic type of the receiver object is T0.
Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression 1.isInstanceOf[String] will return false, while the expression List(1).isInstanceOf[List[String]] will return true. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.
returns
true if the receiver object is an instance of erasure of type T0; false otherwise.
Definition Classes
Any
final def ne(arg0: AnyRef): Boolean
Equivalent to !(this eq that).
Equivalent to !(this eq that).
returns
true if the argument is not a reference to the receiver object; false otherwise.
Definition Classes
AnyRef
final def notify(): Unit
Wakes up a single thread that is waiting on the receiver object's monitor.
Wakes up a single thread that is waiting on the receiver object's monitor.
Definition Classes
AnyRef
Annotations
@native()
Note
not specified by SLS as a member of AnyRef
final def notifyAll(): Unit
Wakes up all threads that are waiting on the receiver object's monitor.
Wakes up all threads that are waiting on the receiver object's monitor.
Definition Classes
AnyRef
Annotations
@native()
Note
not specified by SLS as a member of AnyRef
def out: PrintStream
The default output, can be overridden by withOut
def print(obj: Any): Unit
Prints an object to out using its toString method.
Prints an object to out using its toString method.
obj
the object to print; may be null.
def printf(text: String, args: Any*): Unit
Prints its arguments as a formatted string to the default output, based on a string pattern (in a fashion similar to printf in C).
Prints its arguments as a formatted string to the default output, based on a string pattern (in a fashion similar to printf in C).
The interpretation of the formatting patterns is described in java.util.Formatter.
text
the pattern for formatting the arguments.
args
the arguments used to instantiating the pattern.
Exceptions thrown
java.lang.IllegalArgumentException if there was a problem with the format string or arguments
def println(x: Any): Unit
Prints out an object to the default output, followed by a newline character.
Prints out an object to the default output, followed by a newline character.
x
the object to print.
def println(): Unit
Prints a newline character on the default output.
def setErrDirect(err: PrintStream): Unit
Attributes
protected
def setInDirect(in: BufferedReader): Unit
Attributes
protected
def setOutDirect(out: PrintStream): Unit
Attributes
protected
final def synchronized[T0](arg0: => T0): T0
Definition Classes
AnyRef
def toString(): String
Creates a String representation of this object.
Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.
returns
a String representation of the object.
Definition Classes
AnyRef → Any
final def wait(): Unit
Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.InterruptedException])
final def wait(arg0: Long, arg1: Int): Unit
Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.InterruptedException])
final def wait(arg0: Long): Unit
Definition Classes
AnyRef
Annotations
@throws(classOf[java.lang.InterruptedException]) @native()
def withErr[T](err: OutputStream)(thunk: => T): T
Sets the default error stream for the duration of execution of one thunk.
Sets the default error stream for the duration of execution of one thunk.
err
the new error stream.
thunk
the code to execute with the new error stream active
returns
the results of thunk
See also
withErr[T](err:PrintStream)(thunk: => T)
def withErr[T](err: PrintStream)(thunk: => T): T
Set the default error stream for the duration of execution of one thunk.
Set the default error stream for the duration of execution of one thunk.
err
the new error stream.
thunk
the code to execute with the new error stream active
returns
the results of thunk
Example:
1. withErr(Console.out) { err.println("This goes to default _out_") }
See also
withErr[T](err:OutputStream)(thunk: => T)
def withIn[T](in: InputStream)(thunk: => T): T
Sets the default input stream for the duration of execution of one thunk.
Sets the default input stream for the duration of execution of one thunk.
in
the new input stream.
thunk
the code to execute with the new input stream active
returns
the results of thunk
See also
withIn[T](reader:Reader)(thunk: => T)
def withIn[T](reader: Reader)(thunk: => T): T
Sets the default input stream for the duration of execution of one thunk.
Sets the default input stream for the duration of execution of one thunk.
thunk
the code to execute with the new input stream active
returns
the results of thunk
Example:
1. val someFile:Reader = openFile("file.txt") withIn(someFile) { // Reads a line from file.txt instead of default input println(readLine) }
See also
withIn[T](in:InputStream)(thunk: => T)
def withOut[T](out: OutputStream)(thunk: => T): T
Sets the default output stream for the duration of execution of one thunk.
Sets the default output stream for the duration of execution of one thunk.
out
the new output stream.
thunk
the code to execute with the new output stream active
returns
the results of thunk
See also
withOut[T](out:PrintStream)(thunk: => T)
def withOut[T](out: PrintStream)(thunk: => T): T
Sets the default output stream for the duration of execution of one thunk.
Sets the default output stream for the duration of execution of one thunk.
out
the new output stream.
thunk
the code to execute with the new output stream active
returns
the results of thunk
Example:
1. withOut(Console.err) { println("This goes to default _error_") }
See also
withOut[T](out:OutputStream)(thunk: => T)

Inherited from AnsiColor

Inherited from AnyRef

Inherited from Any

Console Output

These methods provide output via the console.

IO Defaults

These values provide direct access to the standard IO channels

IO Redefinition

These methods allow substituting alternative streams for the duration of a body of code. Threadsafe by virtue of scala.util.DynamicVariable.

Packages

Package structure

Automatic imports

Guide

Common Imports

Specifying Durations

Using Futures For Non-blocking Computation

Avoid Blocking

Console

object Console extends AnsiColor

Console Output

ANSI escape codes

IO redefinition

Value Members

Inherited from AnsiColor

Inherited from AnyRef

Inherited from Any

Console Output

IO Defaults

IO Redefinition

ANSI Style and Control Codes

ANSI Black

ANSI Red

ANSI Green

ANSI Yellow

ANSI Blue

ANSI Magenta

ANSI Cyan

ANSI White

Ungrouped

Packages

Package structure

Automatic imports

Guide

Common Imports

Specifying Durations

Using Futures For Non-blocking Computation

Avoid Blocking

Console

object Console extends AnsiColor

Console Output

ANSI escape codes

IO redefinition

Value Members

Inherited from AnsiColor

Inherited from AnyRef

Inherited from Any

Console Output

IO Defaults

IO Redefinition

ANSI Style and Control Codes

ANSI Black

ANSI Red

ANSI Green

ANSI Yellow

ANSI Blue

ANSI Magenta

ANSI Cyan

ANSI White

Ungrouped

Console