ttyname, ttyname_r - return name of a terminal
char *ttyname(int fd);
int ttyname_r(int fd, char *buf, size_t buflen);
The function ttyname() returns a pointer to the null-terminated pathname
of the terminal device that is open on the file descriptor fd, or NULL
on error (for example, if fd is not connected to a terminal). The
return value may point to static data, possibly overwritten by the next call.
The function ttyname_r() stores this pathname in the buffer buf
of length buflen.
The function ttyname() returns a pointer to a pathname on success. On
error, NULL is returned, and errno is set appropriately. The function
ttyname_r() returns 0 on success, and an error number upon error.
- Bad file descriptor.
- File descriptor does not refer to a terminal device.
- (ttyname_r()) buflen was too small to allow storing the
- File descriptor refers to a slave pseudoterminal device but the
corresponding pathname could not be found (see NOTES).
For an explanation of the terms used in this section, see attributes(7).
POSIX.1-2001, POSIX.1-2008, 4.2BSD.
A process that keeps a file descriptor that refers to a pts(4) device
open when switching to another mount namespace that uses a different
/dev/ptmx instance may still accidentally find that a device path of
the same name for that file descriptor exists. However, this device path
refers to a different device and thus can't be used to access the device that
the file descriptor refers to. Calling ttyname() or ttyname_r()
on the file descriptor in the new mount namespace will cause these functions
to return NULL and set errno to ENODEV.
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