isenv

Determine if environment variable exists

Since R2022b

Syntax

tf = isenv(varname)

Description

tf = isenv(varname) returns a logical array containing 1 (true) where the elements of the varname array are operating system environment variables, and 0 (false) where they are not. The logical array tf has the same dimensions as the input array.

On most UNIX^® platforms, an environment variable can exist with an empty value (""). On the Microsoft^® Windows^® platform, setting the value of an environment variable to "" is equivalent to removing the variable.

Examples

Create and Test Environment Variable

Create environment variable myVar, and then check that it exists.

setenv("myVar","myValue");
isenv("myVar")

ans = logical
   1

Remove myVar, and then check that it no longer exists.

unsetenv("myVar");
isenv("myVar")

ans = logical
   0

Create and Test Multiple Environment Variables

Create multiple environment variables, and then check that they exist.

setenv(["Var1" "Var2" "Var3" "Var4"],["Val1" "Val2" "Val3" "Val4"]);
isenv(["Var1" "Var2"; "Var3" "Var4"])

ans = 2x2 logical array

   1   1
   1   1

Remove two of the environment variables using unsetenv, and then check that they no longer exist.

unsetenv(["Var1" "Var4"]);
isenv(["Var1" "Var2"; "Var3" "Var4"])

ans = 2x2 logical array

   0   1
   1   0

You can also remove environment variables using setenv with missing. Change the value of one environment variable and remove another.

setenv(["Var2" "Var3"],["ValB" missing]);
isenv(["Var1" "Var2"; "Var3" "Var4"])

ans = 2x2 logical array

   0   1
   0   0

Input Arguments

varname — Environment variable names

string scalar | character vector | string array | cell array of character vectors

Environment variable names, specified as a string scalar, character vector, string array, or cell array of character vectors. If specified as a character array, a scalar logical array is returned.

Example: "PATH"

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• Code generation does not support the use of isenv inside parfor loops.

Version History

Introduced in R2022b

R2023a: Test multiple environment variables

Test multiple environment variables by using isenv with a string array or cell array of character vectors as input.