grantptfd

Grantptfd is a nonstandard term appearing in some Unix-like environments to describe an interface that grants access to the slave pseudoterminal (PTY) associated with a master PTY, using a file descriptor rather than a path to the master device. It is related to the standard PTY workflow that includes posix_openpt, grantpt, unlockpt, and ptsname, but grantptfd is not part of the POSIX specification and is not widely documented across major systems.

Concept and purpose

- The function is intended to prepare the slave PTY so that the calling process can open and use it, typically by adjusting permissions and ownership on the slave device.

- It is positioned as an alternative or wrapper around the traditional grantpt(), which performs similar setup for the master PTY’s slave side. The exact behavior and requirements can vary by implementation.

Usage pattern

- A typical PTY workflow begins with obtaining a master file descriptor via posix_openpt() or an equivalent call.

- After acquiring the master FD, grantptfd (if provided by the system) would be invoked to grant access to the corresponding slave PTY.

- The process may then use unlockpt() to unlock the slave name for opening and ptsname() to retrieve the slave’s path, followed by opening the slave device for I/O.

Portability and availability

- grantptfd is not standardized and is not guaranteed to exist on all systems. In most environments, the standard grantpt() function is used, often alongside unlockpt() and ptsname().

- When encountered in code, grantptfd should be treated as platform-specific; consult the local system’s man pages and documentation to confirm its existence and exact behavior.

See also

- grantpt, unlockpt, posix_openpt, ptsname.