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Table of contents

  1. echo, the smart print()
    1. Converting to string
  2. Print to standard error and standard output

echo, the smart print()

In our Hello world example we had to print a text, and we used the echo identifier, that is automatically imported (and it’s part of the system module).

echo will automatically convert the arguments to string, and will add a new line at the end. In the following example we print strings (surrounded by double quotes), a string variable, an integer (returned from the len() function) and even a sequence (list):

  package = "samtools"
  versions = @[0.19, 1.0, 1.4]

echo "We have ", len(versions), " versions of ", package, ": ", versions

The output would be:

We have 3 versions of samtools: @[0.19, 1.0, 1.4]

Converting to string

The $ operator will convert to string it’s operand. echo effectively uses this operator when receiving its typed arguments (in other words, trying to print a type that does not have an overloaded $ will fail).

In the following example we use the concatenation operator (&, see strings) and the conversion to string to produce to produce a string, called packageString, having as content “samtools 0.19”:

  package = "samtools"
  versions = @[0.19, 1.0, 1.4]
  packageString = package & " " & $versions[0]

echo packageString

stdout.writeLine and stderr.writeLine will print, respectively, to the standard output and to the standard error. They will not add a newline.