Write stralloc to buffer and flush
#include <stralloc.h> #include <buffer.h> int buffer_putsaflush(buffer* b,const char* x);
buffer_putsaflush is equivalent to buffer_putflush(b,x.sa,x.len).
0 if everything is fine, -1 on error (setting errno).
buffer_puts(3), buffer_flush(3), buffer(3)