WP_CLI\Utils

isPiped() │ WP-CLI 1.0

Checks whether the output of the current script is a TTY or a pipe / redirect

Returns true if STDOUT output is being redirected to a pipe or a file; false is output is being sent directly to the terminal.

If an env variable SHELL_PIPE exists, returned result depends on its value. Strings like 1, 0, yes, no, that validate to booleans are accepted.

To enable ASCII formatting even when the shell is piped, use the ENV variable SHELL_PIPE=0.

No Hooks.

Return

true|false.

Usage

isPiped();

isPiped() code WP-CLI 2.8.0-alpha

wp-cli/php/utils.php 
function isPiped() { // phpcs:ignore WordPress.NamingConventions.ValidFunctionName.FunctionNameInvalid -- Renaming would break BC.
	$shell_pipe = getenv( 'SHELL_PIPE' );

	if ( false !== $shell_pipe ) {
		return filter_var( $shell_pipe, FILTER_VALIDATE_BOOLEAN );
	}

	return function_exists( 'posix_isatty' ) && ! posix_isatty( STDOUT );
}