setgetty

[John B. Milton]

In article <143 at zebra.UUCP> vern at zebra.UUCP (Vernon C. Hoxie) writes:
>
>	I was looking through the code for 'pcomm2' and saw that they
>had a system('setgetty tty mode') call.  Looking through my manuals, I
>cannot find any reference to this command.  Upon listing the /usr/bin, I
>find that such a command is indeed part of the set.  It has but one link,
>so I infer that it is not an optional entry to some other command.
This is a very simple program that toggles the space/colon at the beginning
of the /etc/inittab file. Unfortunately, it sometimes gets stuck in a loop
looking at the /etc/utmp file and block your port until you kill it. Below
is my simpler version that doesn't lock up

>	Where can I get documentation on this command and how many other
>goodies are present in the system which are not documented?
If you can't find it in the User's Manual Vol I, you're SOL

>	BTW when I was reading about linking 'zcat' to 'compress' to get
>an optional usage, I remembered reading in "UNIX System Administration"
>by David Fiedler and Bruce H. Hunter, Hayden Books, about optional
>commands to 'ls'.  They said that linking 'll' to 'ls' would produce a
>long listing without having to add options.  I tried it and I like it.
>The book lists other links to 'ls' to simulate the '-m', '-r', '-F' and '-x'
>options.  The links are 'l', 'lr', 'lf' and 'lx'.  They are listed on
>page 22 if you have that book.
You should get the full compress distribution, as it comes with some other
programs: atob, btoa, compressdir, tarmail, uncompressdir, untarmail, zcmp,
zdiff, zmore. These are programs, not just links.

Here's the rest of the story:

ls looks at the last two characters of argv[0]:
*[!l]l == ls -m
*ll    == ls -l
*lr    == ls -R
*lf    == ls -F
*lx    == ls -x
*      == ls

There is also a -n switch, which is not documented. It turns on long (-l) mode
and displays the uid/gid as a number instead of text (doesn't open /etc/passwd)
This is also a -A switch, which is on by default if ls is run by root. This
switch shows all .[!.]* files, but not . and ..

I have seen the -n and -A switches properly documented on other UNIX systems.

John (the whole story) Milton
--
John Bly Milton IV, jbm at uncle.UUCP, n8emr!uncle!jbm at osu-cis.cis.ohio-state.edu
(614) h:294-4823, w:764-2933;  Got any good 74LS503 circuits?
---
#! /bin/sh
# This is a shell archive.  Remove anything before this line, then unpack
# it by saving it into a file and typing "sh file".  To overwrite existing
# files, type "sh file -c".  You can also feed this as standard input via
# unshar, or by typing "sh <file", e.g..  If this archive is complete, you
# will see the following message at the end:
#		"End of shell archive."
# Contents:  setgetty.c
# Wrapped by jbm at uncle on Fri Jan 20 04:01:34 1989
PATH=/bin:/usr/bin:/usr/ucb ; export PATH
if test -f 'setgetty.c' -a "${1}" != "-c" ; then 
  echo shar: Will not clobber existing file \"'setgetty.c'\"
else
echo shar: Extracting \"'setgetty.c'\" \(3071 characters\)
sed "s/^X//" >'setgetty.c' <<'END_OF_FILE'
X/* vi:set ts=2 sw=2:
XThis is a replacement for the UNIXpc program "setgetty". This program is run
Xby the files /usr/bin/geto{n|ff}.sh, which are run by the dial(3) library call
Xto get the getty off a tty line when dialing out, and to put it back when done.
XThat's all well and good, except it screws up sometimes and just sits there
Xwith the getty offm chewing up CPU and NOT turning the getty back on. I'm not
Xentirely sure why it gets stuck. I think it has something to do with the fact
Xthat it's looking at the /etc/utmp file to decide if there is currectly a user
Xor login process on the line. This program does not check the utmp file. This
Xis what it DOES do:
X
X1. Open /etc/inittab r/w
X2. Read the whole thing into a buffer in one call
X3. Finds the first occurance of the right label
X3. Sets the first character to a space or colon
X4. If a change was done, it writes the inittab back out in one call.
X
XYou may ask "What, documentation, what is this?". Well, this program, like
Xsetgetty has to have the executable owned by and setuid root:
X-rwsr-xr-x  1 root    bin        2156 Jan  1  1970 /usr/bin/setgetty
X
XInstalltion:
X1. cc -cO -o sg.o sg.c
X2. ld -s -o sg /lib/crt0s.o /lib/shlib.ifile sg.o
X3. chown root sg
X4. chmod 4755 sg
X5. mv /usr/bin/setgetty /usr/bin/osetgetty
X6. mv sg /usr/bin/setgetty
X
XFor some reason, cu and uucico through dial(3) don't run getoff.sh when the
Xprogram running on the line is not a LOGIN process. Hmm, beats me. As always,
Xlet me know if you have any problems: John B. Milton, jbm at uncle
X*/
X
X#include <fcntl.h>
X#include <stdio.h>
X#include <string.h>
X
X#define BUFSIZE 4096
X
Xextern int errno;
X
Xvoid qperrorf(format,a1,a2,a3,a4,a5,a6,a7,a8,a9,a10)
Xchar *format,*a1,*a2,*a3,*a4,*a5,*a6,*a7,*a8,*a9;
X{
X	char line[200];
X	int curerrno=errno;
X	sprintf(line,format,a1,a2,a3,a4,a5,a6,a7,a8,a9);
X	errno=curerrno;
X	perror(line);
X	exit(curerrno);
X}
X
Xstatic char *usage="Usage: %s xxx 0|1\n";
Xstatic char *it="/etc/inittab";
X
Xint main(argc,argv)
Xint argc;
Xchar *argv[];
X{
X	int f,len;
X	char look,new,*s,buf[BUFSIZE];
X
X	if (argc!=3 || strlen(argv[1])!=3 || (argv[2][0]!='0' && argv[2][0]!='1')) {
X		fprintf(stderr,usage,argv[0]);
X		exit(0);
X	}
X	if ((f=open(it,O_RDWR))==-1)
X		qperrorf("%s: open r/w %s",argv[0],it);
X	if ((len=read(f,buf,BUFSIZE))==-1)
X		qperrorf("%s: read %s",argv[0],it);
X	if (len==BUFSIZE) {
X		fprintf(stderr,"%s: error, BUFSIZE too small\n",argv[0]);
X		exit(3); /* new status, setgetty didn't have this one */
X	}
X	if (argv[2][0]-'0') { look=':'; new=' '; } else { look=' '; new=':'; }
X	for (s=buf; s<buf+BUFSIZE-20; s++)
X		if (*s=='\n' && (*(s+1)==' ' || *(s+1)==':') && strncmp(s+2,argv[1],3)==0) {
X			if (*(s+1)!=new) {
X				*(s+1)=new;
X				lseek(f,0,0);
X				if ((len=write(f,buf,len))==-1)
X					qperrorf("%s: re-write %s",argv[0],it);
X				if (close(f)==-1)
X					qperrorf("%s: close %s",argv[0],it);
X				kill(1,1); /* very quick telinit Q */
X			}
X			if (new==' ')
X				exit(0); /* dial(3) doesn't care about turning the getty on */
X			else
X				exit(2); /* this is success, believe it or not */
X		}
X	exit(1); /* line not found */
X}
END_OF_FILE
if test 3071 -ne `wc -c <'setgetty.c'`; then
    echo shar: \"'setgetty.c'\" unpacked with wrong size!
fi
# end of 'setgetty.c'
fi
echo shar: End of shell archive.
exit 0