Taking Input from Users in Julia

Reading user input is a way of interaction between the program and the user. User inputs are necessary in case of testing a piece of code with varying and legitimate inputs.

Reading user inputs from console in Julia can be done through inbuilt I/O methods like :

• readline()
• readlines()

Using readline() Function

readline() method reads a line of text from the input stream (STDIN) until a ‘\n’ (newline) character is encountered. The input is read as String data.

Syntax:

s = readline()

Example 1:
In the below example, user input is obtained using the readline() method. We can prompt the user with the help of a print statement prior. It is to be noted that readline method reads the input into a string data type.

# Julia program to take input from user

# prompt to input
print("What's your name ? \n\n")

# Calling rdeadline() function
name = readline()

println("The name is ", name)
print("\n\n")

# typeof() determines the datatype.
println("Type of the input is: ", typeof(name))

Output :

Example 2: Reading numerical data types from console

The below example demonstrates how to read inputs as numbers and make use of them in further computations. This is done using the parse() method, using which we can convert a numeric string(Float or Int) into a numerical value.

# Julia program to calculate sum of
# 5 integers obtained from console/user input

result = 0

# Prompt to enter
println("Enter 5 numbers line by line")

# Taking Input from user
for number in 1:5

   num = readline()
   num = parse(Int64, num)
   global result+= num

end

println("The sum is :", result)

Output:

Using readlines() Function

readlines() method is used to read N lines of text input from the console. N lines are stored as the entries of a one-dimensional String array. Here lines must be delimited with newline character or by pressing the “ENTER” key. To stop taking Input press Ctrl-D.

Syntax:

lines = readlines()

Example 1: Reading N lines of input from STDIN
In the below example N-lines of input are obtained and stored within a 1-D String Array. We can access the desired line using it’s index.

# Julia program to take
# multi-lined input from user

line_count = 0

println("Enter multi-lined text, press Ctrl-D when done")

# Calling readlines() function
lines = readlines()

# Loop to count lines
for line in lines

   global line_count += 1

end

println("total no.of.lines : ", line_count)

println(lines)

# Getting type of Input values
println("type of input: ", typeof(lines))

Output:

Example 2

In the below example we input N lines and display the entries by prefixing with their entry numbers.

line_number = 1

println("Enter few paragraphs")

print("\n")

lines = readlines()

println()

for line in lines

   println(line_number, ". ", line)
   global line_number += 1

end

Output: