Tex. Code of Criminal Procedure § 42.034

(a) If jail time has been awarded to a person sentenced for a misdemeanor or sentenced to confinement in the county jail for a felony, the trial judge at the time of pronouncement of sentence or at any time while the defendant is serving the sentence, when in the judge's discretion the ends of justice would best be served, may require the defendant to serve an alternate term for the same period of time in the county jail work release program of the county in which the offense occurred, if the person is classified by the sheriff as a low-risk offender under the classification system developed by the Commission on Jail Standards under Section 511.009, Government Code.

(b) The sheriff shall provide a classification report for a defendant to a judge as necessary so that the judge can determine whether to require the defendant to participate in the work release program under this article.

(c) A defendant sentenced under this article who would otherwise be sentenced to confinement in jail may earn good conduct credit in the same manner as provided by Article 42.032 of this code, but only while actually confined.