The functions described in this chapter only work on files that
correspond to terminal devices. You can find out whether a file
descriptor is associated with a terminal by using the
Prototypes for the functions in this section are declared in the header file unistd.h.
This function returns
1if filedes is a file descriptor associated with an open terminal device, and 0 otherwise.
If a file descriptor is associated with a terminal, you can get its
associated file name using the
ttyname function. See also the
ctermid function, described in Identifying the Terminal.
If the file descriptor filedes is associated with a terminal device, the
ttynamefunction returns a pointer to a statically-allocated, null-terminated string containing the file name of the terminal file. The value is a null pointer if the file descriptor isn't associated with a terminal, or the file name cannot be determined.
ttyname_rfunction is similar to the
ttynamefunction except that it places its result into the user-specified buffer starting at buf with length len.
The normal return value from
ttyname_ris 0. Otherwise an error number is returned to indicate the error. The following
errnoerror conditions are defined for this function:
- The filedes argument is not a valid file descriptor.
- The filedes is not associated with a terminal.
- The buffer length len is too small to store the string to be returned.