lock file program
Steve Barber
steveb at shade.UUCP
Sun Dec 10 15:42:17 AEST 1989
Original-posting-by: steveb at shade.UUCP (Steve Barber)
Reposted-by: emv at math.lsa.umich.edu (Edward Vielmetti)
Posting-id: 891210.0443
Posting-number: Volume TEST, Number TEST
Archive-name: HDB-lock-KA9Q
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[Comments on this service to emv at math.lsa.umich.edu (Edward Vielmetti)]
Enclosed in this SHAR file are a variety of things:
lock.c Source for the HDB-format lockfile utilities.
Don't hold your breath, this program is just a
quick hack that I just tacked some documentation
onto.
ka9q A shell script showing how to use lock with KA9Q.
startup.net The startup.net file I use with KA9Q to connect
to Merit with the SLFP protocol, since I've gotten
a few questions about it.
Have fun with them!
Steve Barber
steveb at shade.Ann-Arbor.MI.US
------------------------------------------------------------------------------
#! /bin/sh
# This is a shell archive, meaning:
# 1. Remove everything above the #! /bin/sh line.
# 2. Save the resulting text in a file.
# 3. Execute the file with /bin/sh (not csh) to create:
# README
# lock.c
# ka9q
# startup.net
# This archive created: Sat Dec 9 17:24:40 1989
export PATH; PATH=/bin:/usr/bin:$PATH
echo shar: "extracting 'README'" '(373 characters)'
if test -f 'README'
then
echo shar: "will not over-write existing file 'README'"
else
sed 's\/^XX\/\/' << \SHAR_EOF > 'README'
XXEnclosed in this SHAR file are a variety of things:
XX
XX lock.c Source for the HDB-format lockfile utilities
XX
XX ka9q A shell script showing how to use lock with KA9Q
XX
XX startup.net The startup.net file I use with KA9Q to connect
XX to Merit with the SLFP protocol, since I've gotten
XX a few questions about it.
XX
XXHave fun with them!
XX
XXSteve Barber
XXsteveb at shade.Ann-Arbor.MI.US
SHAR_EOF
if test 373 -ne "`wc -c < 'README'`"
then
echo shar: "error transmitting 'README'" '(should have been 373 characters)'
fi
fi
echo shar: "extracting 'lock.c'" '(4221 characters)'
if test -f 'lock.c'
then
echo shar: "will not over-write existing file 'lock.c'"
else
sed 's\/^XX\/\/' << \SHAR_EOF > 'lock.c'
XX/*
XX * lock.c - establish an exclusive lock file in a directory storing a
XX * binary id number in the lockfile for authentication purposes. (The
XX * format of the contents of the lockfile just happens to correspond to
XX * the format used by the implementation of HDB UUCP on the AT&T 3B1.)
XX *
XX * by Stephen W. Barber (steveb at shade.Ann-Arbor.MI.US)
XX *
XX * This utility is hereby placed in the public domain for all to use
XX * and modify as they see fit. There are no warranties, and I can not
XX * be held liable for any damages caused by this program. If you do
XX * have a problem though feel free to write me and I'll help you if I can.
XX *
XX * I prefer that if you have to make changes, that you document them in
XX * this header comment, and that you implement them using an appropriate
XX * #ifdef statement so that the base version can still be compiled from
XX * your source. You might also send me any patches you make, if you feel
XX * they are important.
XX *
XX * SIMPLIFIED PSEUDOCODE FOR HOW IT WORKS:
XX * =======================================
XX * - set done flag to false
XX * - set count
XX * - loop while not done and count > 0
XX * - open(".../LOCK", O_CREAT, 0644)
XX * - if it fails,
XX * + sleep for a while
XX * + count--
XX * - else
XX * + close the file
XX * + done=TRUE
XX * - endif
XX * - endloop
XX *
XX * INSTALLATION:
XX * =============
XX * Compile lock.c. It requires no special options, so
XX * cc -O lock.c -o lock
XX * should work just fine. Next, install the lock executable in an
XX * appropriate directory (mine's in /usr/local):
XX * cp lock /usr/local
XX * Finally, make a link to lock named "unlock":
XX * cd /usr/local
XX * ln lock unlock
XX *
XX * USAGE:
XX * ======
XX * To establish a lock, issue the command:
XX * lock directory lockname id retries wait
XX * where directory is the name of the directory to create the lockfile in,
XX * lockname is the name of the lockfile to create, id is a numerical id
XX * (intended to be a process id, but could be anything), retries is the
XX * number of times to try again if a lock already exists, and wait is the
XX * number of seconds to wait between attempts. The result code ($? in
XX * sh and ksh, $status in csh) will be 0 if a lock is create successfully,
XX * or any of several various non-zero numbers depending on the nature of
XX * the failure.
XX *
XX * To release the lock:
XX * unlock directory lockname id
XX * The lock will not be removed if the id does not match the one used when
XX * the lockfile was created, and an error code will be returned.
XX *
XX */
XX
XX#include <stdio.h>
XX#include <fcntl.h>
XX#include <errno.h>
XX
XXvoid my_lock(), my_unlock();
XX
XXmain(argc, argv)
XXint argc;
XXchar *argv[];
XX{
XX if (!strcmp("lock", argv[0]))
XX {
XX if (argc != 6)
XX {
XX fprintf(stderr, "lock: invalid arguments\n");
XX fprintf(stderr,
XX "Usage: lock dir name id retries wait\n");
XX exit(2);
XX }
XX my_lock(argv[1], argv[2], argv[3], argv[4], argv[5]);
XX exit(0);
XX }
XX else if (!strcmp("unlock", argv[0]))
XX {
XX if (argc != 4)
XX {
XX fprintf(stderr, "unlock: invalid arguments\n");
XX fprintf(stderr,
XX "Usage: unlock dir name id\n");
XX exit(2);
XX }
XX my_unlock(argv[1], argv[2], argv[3]);
XX exit(0);
XX }
XX else
XX {
XX fprintf(stderr,
XX "Eh? this program should be named lock or unlock!\n");
XX exit(2);
XX }
XX}
XX
XX
XXvoid my_lock(dir, name, id, ret, wait)
XXchar *dir, *name, *id, *ret, *wait;
XX{
XX short retries, idle;
XX int fd, pid;
XX
XX retries = (short) atoi(ret);
XX idle = (short) atoi(wait);
XX pid = atoi(id);
XX if (retries < 1 || retries > 50)
XX retries = 5; /* 5 retries by default */
XX if (idle < 1 || idle > 900)
XX idle = 60; /* 5 minutes by default */
XX if (chdir(dir) == -1)
XX {
XX fprintf(stderr, "Bad directory %s\n", dir);
XX exit(2);
XX }
XX while (retries > 0)
XX {
XX if ((fd = open(name, O_CREAT | O_EXCL | O_WRONLY, 0644)) == -1)
XX {
XX if (errno != EEXIST)
XX {
XX fprintf(stderr, "Bad file %s\n", name);
XX exit(2);
XX }
XX sleep(idle);
XX retries--;
XX }
XX else
XX {
XX write(fd, &pid, sizeof(pid));
XX close(fd);
XX exit(0);
XX }
XX }
XX exit(1);
XX}
XX
XXvoid my_unlock(dir, name, id)
XXchar *dir, *name, *id;
XX{
XX int fd, pid;
XX
XX if (chdir(dir) == -1)
XX exit(2);
XX if ((fd = open(name, O_RDONLY)) == -1)
XX exit(3);
XX read(fd, &pid, sizeof(pid));
XX close(fd);
XX if (pid != atoi(id))
XX exit(1);
XX if (unlink(name) == -1)
XX exit(4);
XX exit(0);
XX}
SHAR_EOF
if test 4221 -ne "`wc -c < 'lock.c'`"
then
echo shar: "error transmitting 'lock.c'" '(should have been 4221 characters)'
fi
fi
echo shar: "extracting 'ka9q'" '(1076 characters)'
if test -f 'ka9q'
then
echo shar: "will not over-write existing file 'ka9q'"
else
sed 's\/^XX\/\/' << \SHAR_EOF > 'ka9q'
XX#!/bin/sh
XX#
XX# Example application script for the lock/unlock utilities using
XX# the KA9Q (net) package, which should create a lock file for the
XX# device but doesn't.
XX
XX# All KA9Q-related files (including the executable) are kept in $NETHOME
XXNETHOME=/usr/local/lib/KA9Q ; export NETHOME
XXNETSPOOL=/usr/local/lib/KA9Q ; export NETSPOOL
XXPATH=/usr/local/lib/KA9Q:/usr/local:/bin:/usr/bin ; export PATH
XX
XX# Attempt to create a lockfile for tty002 (my modem) using this shell script's
XX# PID, with 2 attempts and a 5 second pause between attempts.
XXlock /usr/spool/uucp LCK..tty002 $$ 2 5
XX
XX# If the result code $? does not equal 0, the lock file could not be created.
XXif [ $? -ne 0 ]
XXthen
XX echo "Device tty002 is busy now; please try again later."
XX exit 1
XXfi
XX
XX# Start up KA9Q and wait around for it to exit.
XXnet
XX
XX# Now remove the lockfile.
XXunlock /usr/spool/uucp LCK..tty002 $$
XX
XX# if we got an error removing the lockfile then something nuked our lockfile
XX# (and possibly installed its own...)
XXif [ $? -ne 0 ]
XXthen
XX echo "Uh oh!! Can't remove my lockfile! I'm sick!!"
XX exit 2
XXfi
XXexit 0
SHAR_EOF
if test 1076 -ne "`wc -c < 'ka9q'`"
then
echo shar: "error transmitting 'ka9q'" '(should have been 1076 characters)'
fi
chmod +x 'ka9q'
fi
echo shar: "extracting 'startup.net'" '(4716 characters)'
if test -f 'startup.net'
then
echo shar: "will not over-write existing file 'startup.net'"
else
sed 's\/^XX\/\/' << \SHAR_EOF > 'startup.net'
XX#
XX# The configuration file for the NET.EXE program...
XX#
XX# Note: NET.EXE ignores all lines beginning with a pound sign (#).
XX#
XX# **********************************************************
XX# **** Read USEGUIDE.DOC to help understand this file! *****
XX# **********************************************************
XX#
XX# There are many commands which must be provided to NET.EXE
XX# each time it is started to configure the program. To keep
XX# from having to type them by hand each time, we put them in
XX# this file, which is read each time NET starts up. Commands
XX# in this configuration file are entered exactly as they would
XX# be typed at the keyboard in the program.
XX#
XX#
XX#-----------------------------------------------
XX#
XX# This entry tells NET.EXE the name of your machine.
XX#
XXhostname shade.ann-arbor.mi.us
XX#
XX#-----------------------------------------------
XX#
XX# The attach command tells NET.EXE about the interfaces in your computer
XX# that you will be using for TCP/IP. These can include normal IBM-type
XX# serial "comm ports", Ethernet controllers, or dedicated packet cards.
XX#
XX# The syntax is:
XX# attach <hw type> <I/O address> <vector> <mode> <label> <bufsize>
XX# <mtu> [<speed>]
XX#
XX# NOTE: /dev/tty002nb is a nonblocking device otherwise equivalent to
XX# /dev/tty002. On a 3B1, this can be created by using
XX# "ls -li /dev/tty002" and noting the major and minor device numbers,
XX# then using the mknod command to create /dev/tty002nb with the same
XX# major device number, and a minor device number of 128+the old minor
XX# device number. This is needed since my modem drops CD when no
XX# carrier is present.
XX#
XX# NOTE: (906) 487-1517 is the number for Merit in Houghton. SLFP has been
XX# proven to work fine with this number. 300, 1200, and 2400 baud
XX# connections are supported here, although I've only used SLFP at
XX# 2400 baud. If you have problems with a Merit number in a low-
XX# (computer-)population area, you might try it once with this number
XX# or the Ann Arbor number, (313) 764-4800
XX#
XXattach asy 0 /dev/tty002nb slfp sf0 4096 400 2400 ATDT4871517
XX#
XX# See USEGUIDE.DOC for explanation of the attach command and its options.
XX#
XX# Merit Users Only:
XX# If you think you have everything right, you can try calling the folks
XX# at Merit. Their number is: (313) 764-9430. Be patient. They receive
XX# a large number of calls. Note that they have little knowledge about
XX# KA9Q itself. The type of problem they're best equipped to handle is
XX# determining whether your hard-wired Merit line is functioning properly.
XX# If you don't have a hard-wired Merit line, Merit is just not going to
XX# be able to help you.
XX#
XX#-------------------------------------------------
XX#
XX# Print out the IP address that we were assigned by the SLFP host:
XX#
XX! echo "Assigned IP address is \\c"
XXip addr
XX#
XX#-------------------------------------------------
XX#
XX# The following entry tells the program to route all packets out
XX# the interface labeled sf0 in the attach command.
XX#
XXroute add default sf0
XX#
XX#-------------------------------------------------
XX#
XX# Time To Live is the maximum number of hops a packet can take
XX# before it is thrown away. This command prevents an inadvertent
XX# infinite loop from occuring with packets in the network.
XX#
XXip ttl 127
XX#
XX#-------------------------------------------------
XX#
XX# The Maximum Segment Size is the largest single transmission that
XX# you will send. An mss of 216 corresponds to the mtu of 256 set
XX# up in the attach command above, overhead bytes considered.
XX#
XX# tcp mss 192
XXtcp mss 360
XX#
XX#-------------------------------------------------
XX#
XX# The Window parameter establishes the maximum number of bytes
XX# that may be outstanding before your system expects an ack.
XX# If window is twice as big as mss, for example, there will be two
XX# active packets on the channel at any given time... large values of
XX# window provide improved throughput on full-duplex links, but are a
XX# problem on the air. Keep mss <= window <= 2*mss if you're on the air.
XX#
XX#
XX#tcp window 768
XXtcp window 2160
XX#
XX#-------------------------------------------------
XX#
XX# This entry will open the specified log file and will
XX# record the server activity of your system. If you don't want a log,
XX# comment out this line.
XX#
XXlog /tmp/net.log
XX#
XX#-------------------------------------------------
XX#
XX# Each of the servers (services you will provide) must be turned
XX# on before they will be active. The following entries turn all
XX# of them on. To turn any function off use the command 'stop' after
XX# NET gets fired up, or just comment out the line here.
XX#
XXstart smtp
XXstart ftp
XXstart echo
XXstart discard
XXstart telnet
XX#
XX#---------------------------------------------------
XX# THE END
SHAR_EOF
if test 4716 -ne "`wc -c < 'startup.net'`"
then
echo shar: "error transmitting 'startup.net'" '(should have been 4716 characters)'
fi
fi
exit 0
# End of shell archive
--
--**-Steve Barber----steveb at shade.Ann-Arbor.MI.US----(cmode)-------------------
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