Convenience macro for libssh2_channel_write_ex(3)
#include <libssh2.h> ssize_t libssh2_channel_write_stderr(LIBSSH2_CHANNEL *channel, const char *buf, size_t buflen);
This is a macro defined in a public libssh2 header file that is using the underlying function libssh2_channel_write_ex(3).