GETTTYENT(3) Linux Programmer's Manual GETTTYENT(3)

getttyent, getttynam, setttyent, endttyent - get ttys file entry

#include <ttyent.h>
struct ttyent *getttyent(void);
struct ttyent *getttynam(const char *name);
int setttyent(void);
int endttyent(void);

These functions provide an interface to the file _PATH_TTYS (e.g., /etc/ttys).
The function setttyent() opens the file or rewinds it if already open.
The function endttyent() closes the file.
The function getttynam() searches for a given terminal name in the file. It returns a pointer to a ttyent structure (description below).
The function getttyent() opens the file _PATH_TTYS (if necessary) and returns the first entry. If the file is already open, the next entry. The ttyent structure has the form:

struct ttyent {
    char *ty_name;     /* terminal device name */
    char *ty_getty;    /* command to execute, usually getty */
    char *ty_type;     /* terminal type for termcap */
    int   ty_status;   /* status flags */
    char *ty_window;   /* command to start up window manager */
    char *ty_comment;  /* comment field */

ty_status can be:

#define TTY_ON     0x01  /* enable logins (start ty_getty program) */
#define TTY_SECURE 0x02  /* allow UID 0 to login */

For an explanation of the terms used in this section, see attributes(7).
Interface Attribute Value
getttyent (), setttyent (), endttyent (), getttynam () Thread safety MT-Unsafe race:ttyent

Not in POSIX.1. Present on the BSDs, and perhaps other systems.

Under Linux, the file /etc/ttys, and the functions described above, are not used.

ttyname(3), ttyslot(3)
2017-09-15 GNU