Cygwin's default user interface will be the bash shell working inside the mintty terminal emulator.[25] The DLL also implements pseudo terminal (pty) units, and Cygwin ships with several terminal emulators which might be determined by them, like rxvt/urxvt and xterm. The Model of GCC that includes Cygwin has different extensions https://acgwin29639.bloguetechno.com/getting-my-acgwin-to-work-72572983