EXIST Test for Existence

Section: Inspection Functions

Usage

Tests for the existence of a variable, function, directory or file. The general syntax for its use is
  y = exist(item,kind)

where item is a string containing the name of the item to look for, and kind is a string indicating the type of the search. The kind must be one of

You can also leave the kind specification out, in which case the calling syntax is
  y = exist(item)

The return code is one of the following:

Note: previous to version 1.10, exist used a different notion of existence for variables: a variable was said to exist if it was defined and non-empty. This test is now performed by isset.

Example

Some examples of the exist function. Note that generally exist is used in functions to test for keywords. For example,
  function y = testfunc(a, b, c)
  if (~exist('c'))
    % c was not defined, so establish a default
    c = 13;
  end
  y = a + b + c;

An example of exist in action.

--> a = randn(3,5,2)

a = 

(:,:,1) = 

    0.8887   -0.2749   -0.1202    0.2347    0.2815 
   -0.9052    0.2688    1.9047   -0.0533   -1.6196 
   -1.6519    0.1689    0.5134   -0.5795    0.7863 

(:,:,2) = 

    0.8246   -0.5823   -0.6986    0.3591   -2.5987 
   -0.5022    2.4368    1.2679   -1.4748   -0.4239 
   -0.9966   -0.5530   -0.3325    2.2984    0.5024 

--> b = []

b = 
  []
--> who
  Variable Name      Type   Flags             Size
              a    double                    [3 5 2]
              b    double                    [0 0]
--> exist('a')

ans = 

 1 

--> exist('b')

ans = 

 1 

--> exist('c')

ans = 

 0 

--> 
quit