  We prove the Harnack inequality and boundary Harnack principle for the
absolute value of a one-dimensional recurrent subordinate Brownian motion
killed upon hitting $0$, when $0$ is regular for itself and the Laplace
exponent of the subordinator satisfies certain global scaling conditions. Using
the conditional gauge theorem for symmetric Hunt processes we prove that the
Green function of this process killed outside of some interval $(a,b)$ is
comparable to the Green function of the corresponding killed subordinate
Brownian motion. We also consider several properties of the compensated
resolvent kernel $h$, which is harmonic for our process on $(0,1)$.
