What command allows you to execute a command with a modified environment?

The command that allows you to execute a command with a modified environment is 'env'. This command is particularly useful because it lets you specify a temporary set of environment variables for the execution of a command. When you use 'env', you can override the existing environment variables or add new ones that will only be in effect for the duration of that specific command execution.

For example, you might want to run a program with a different PATH or other environment variables without altering your current shell environment. Running env VAR=value command runs 'command' with 'VAR' set to 'value', leaving your original environment intact afterward.

The other options provide related but different functionality. The 'set' command is used to set shell options and positional parameters in a shell session but does not modify the environment of a specific command execution. The 'source' command is used to execute commands from a file in the current shell context, which affects the current environment but does not specifically allow for temporary changes during a command execution. The 'export' command is used to set environment variables in the current shell but does not execute a command with an altered environment.