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?: Elvis Operator

Laurence MorganAbout 1 min

?: Elvis Operator

Returns the right operand if the left operand is falsy (expression)


The Elvis Operator is a little like a conditional where the result of the operation is the first non-falsy value from left to right.

A falsy value is any of the following:

  • an unset / undefined variable
  • any value with a null data type
  • a str or generic with the value false, null, 0, no, off, fail, failed, or disabled
  • a number (num, float or int) with the value 0
  • an empty object or zero length array
  • and, of course, a boolean with the value false


Assign a variable with a default value:

» $foo = $bar ?: "baz"

If $bar is falsy, then the value of $foo will be "baz".

Multiple elvis operators:

» $unset_variable ?: null ?: false ?: "foobar"


Whats in a name?

Wikipediaopen in new window explains this best where it says:

The name "Elvis operator" refers to the fact that when its common notation, ?:, is viewed sideways, it resembles an emoticon of Elvis Presley with his signature hairstyle.

See Also

  • Pipeline: Overview of what a "pipeline" is
  • Schedulers: Overview of the different schedulers (or 'run modes') in Murex
  • && And Logical Operator: Continues next operation if previous operation passes
  • ?? Null Coalescing Operator: Returns the right operand if the left operand is empty / undefined (expression)
  • ? STDERR Pipe: Pipes STDERR from the left hand command to STDIN of the right hand command (DEPRECATED)
  • err: Print a line to the STDERR
  • expr: Expressions: mathematical, string comparisons, logical operators
  • out: Print a string to the STDOUT with a trailing new line character
  • try: Handles non-zero exits inside a block of code
  • trypipe: Checks for non-zero exits of each function in a pipeline
  • || Or Logical Operator: Continues next operation only if previous operation fails
  • null: null function. Similar to /dev/null

This document was generated from gen/expr/elvis_op_doc.yamlopen in new window.

Last update:
Contributors: Laurence Morgan