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	getty.c - ubase - suckless linux base utils
	git clone git://git.suckless.org/ubase
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	---
	getty.c (2823B)
	---
	1 /* See LICENSE file for copyright and license details. */
	2 #include <sys/ioctl.h>
	3 #include <sys/stat.h>
	4 #include <sys/types.h>
	5
	6 #include <fcntl.h>
	7 #include <limits.h>
	8 #include <signal.h>
	9 #include <stdio.h>
	10 #include <stdlib.h>
	11 #include <string.h>
	12 #include <unistd.h>
	13 #include <utmp.h>
	14
	15 #include "config.h"
	16 #include "util.h"
	17
	18 static char *tty = "/dev/tty1";
	19 static char *defaultterm = "linux";
	20
	21 static void
	22 usage(void)
	23 {
	24 eprintf("usage: %s [tty] [term] [cmd] [args...]\n", argv0);
	25 }
	26
	27 int
	28 main(int argc, char *argv[])
	29 {
	30 char term[128], logname[LOGIN_NAME_MAX], c;
	31 char hostname[HOST_NAME_MAX + 1];
	32 struct utmp usr;
	33 struct sigaction sa;
	34 FILE *fp;
	35 int fd;
	36 unsigned int i = 0;
	37 ssize_t n;
	38 long pos;
	39
	40 ARGBEGIN {
	41 default:
	42 usage();
	43 } ARGEND;
	44
	45 strlcpy(term, defaultterm, sizeof(term));
	46 if (argc > 0) {
	47 tty = argv[0];
	48 if (argc > 1)
	49 strlcpy(term, argv[1], sizeof(term));
	50 }
	51
	52 sa.sa_handler = SIG_IGN;
	53 sa.sa_flags = 0;
	54 sigemptyset(&sa.sa_mask);
	55 sigaction(SIGHUP, &sa, NULL);
	56
	57 setenv("TERM", term, 1);
	58
	59 setsid();
	60
	61 fd = open(tty, O_RDWR);
	62 if (fd < 0)
	63 eprintf("open %s:", tty);
	64 if (isatty(fd) == 0)
	65 eprintf("%s is not a tty\n", tty);
	66
	67 /* steal the controlling terminal if necessary */
	68 if (ioctl(fd, TIOCSCTTY, (void *)1) != 0)
	69 weprintf("TIOCSCTTY: could not set controlling tty\n");
	70 vhangup();
	71 close(fd);
	72
	73 fd = open(tty, O_RDWR);
	74 if (fd < 0)
	75 eprintf("open %s:", tty);
	76 dup2(fd, 0);
	77 dup2(fd, 1);
	78 dup2(fd, 2);
	79 if (fchown(fd, 0, 0) < 0)
	80 weprintf("fchown %s:", tty);
	81 if (fchmod(fd, 0600) < 0)
	82 weprintf("fchmod %s:", tty);
	83 if (fd > 2)
	84 close(fd);
	85
	86 sa.sa_handler = SIG_DFL;
	87 sa.sa_flags = 0;
	88 sigemptyset(&sa.sa_mask);
	89 sigaction(SIGHUP, &sa, NULL);
	90
	91 /* Clear all utmp entries for this tty */
	92 fp = fopen(UTMP_PATH, "r+");
	93 if (fp) {
	94 do {
	95 pos = ftell(fp);
	96 if (fread(&usr, sizeof(usr), 1, fp) != 1)
	97 break;
	98 if (usr.ut_line[0] == '\0')
	99 continue;
	100 if (strcmp(usr.ut_line, tty) != 0)
	101 continue;
	102 memset(&usr, 0, sizeof(usr));
	103 fseek(fp, pos, SEEK_SET);
	104 if (fwrite(&usr, sizeof(usr), 1, fp) != 1)
	105 break;
	106 } while (1);
	107 if (ferror(fp))
	108 weprintf("%s: I/O error:", UTMP_PATH);
	109 fclose(fp);
	110 }
	111
	112 if (argc > 2)
	113 return execvp(argv[2], argv + 2);
	114
	115 if (gethostname(hostname, sizeof(hostname)) == 0)
	116 printf("%s ", hostname);
	117 printf("login: ");
	118 fflush(stdout);
	119
	120 /* Flush pending input */
	121 ioctl(0, TCFLSH, (void *)0);
	122 memset(logname, 0, sizeof(logname));
	123 while (1) {
	124 n = read(0, &c, 1);
	125 if (n < 0)
	126 eprintf("read:");
	127 if (n == 0)
	128 return 1;
	129 if (i >= sizeof(logname) - 1)
	130 eprintf("login name too long\n");
	131 if (c == '\n' \|\| c == '\r')
	132 break;
	133 logname[i++] = c;
	134 }
	135 if (logname[0] == '-')
	136 eprintf("login name cannot start with '-'\n");
	137 if (logname[0] == '\0')
	138 return 1;
	139 return execlp("/bin/login", "login", "-p", logname, NULL);
	140 }