tcgetsid(3) Library Functions Manual tcgetsid(3)

tcgetsidget the process group ID for the session leader for the controlling terminal

#include <termios.h>

pid_t
tcgetsid(int fildes);

The () function obtains the process group ID of the session for which the terminal specified by fildes is the controlling terminal.

Upon successful completion, tcgetsid() returns the process group ID associated with the terminal. Otherwise, a value of (pid_t)-1 is returned and errno is set to indicate the error.

The tcgetsid() function will fail if:

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The fildes argument is not associated with a controlling terminal.
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The fildes argument is not a valid file descriptor.
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The file associated with fildes is not a terminal.

getsid(2), setpgid(2), setsid(2), tcgetpgrp(3), termios(4)

The tcgetsid() function conforms to IEEE Std 1003.1-2001 (“POSIX.1”).

December 20, 2003 macOS 15.2