Searches for information about an Internet host by name or IP address, using DNS.
bash$ host surfacemail.com surfacemail.com. has address 202.92.42.236
Displays IP information for a host. With the -h option,
ipcalc does a reverse DNS lookup, finding the name of the
host (server) from the IP address.
bash$ ipcalc -h 202.92.42.236 HOSTNAME=surfacemail.com
Do an Internet "name server lookup" on a host by IP address. This is
essentially equivalent to ipcalc -h or dig -x. The
command may be run either interactively or noninteractively, i.e.,
from within a script.
bash$ nslookup -sil 66.97.104.180 nslookup kuhleersparnis.ch Server: 135.116.137.2 Address: 135.116.137.2#53
Non-authoritative answer: Name: kuhleersparnis.ch
Domain Information Groper. Similar to nslookup,
dig does an Internet name server lookup on a host. May be
run from the command-line or from within a script.
Some interesting options to dig are +time=N for setting a query
timeout to N seconds, +nofail for continuing to query servers
until a reply is received, and -x for doing a reverse address
lookup.
Compare the output of dig -x with ipcalc -h and
nslookup.
bash$ dig -x 81.9.6.2 ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 11649 ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
;; QUESTION SECTION: ;2.6.9.81.in-addr.arpa. IN PTR
;; AUTHORITY SECTION: 6.9.81.in-addr.arpa. 3600 IN SOA ns.eltel.net. noc.eltel.net. 2002031705 900 600 86400 3600
;; Query time: 537 msec ;; SERVER: 135.116.137.2#53(135.116.137.2) ;; WHEN: Wed Jun 26 08:35:24 2002 ;; MSG SIZE rcvd: 91
Finding out where to report a spammer
#!/bin/bash # spam-lookup.sh: Look up abuse contact to report a spammer. # Thanks, Michael Zick.
# Check for command-line arg. ARGCOUNT=1 E_WRONGARGS=85 if [ $# -ne "$ARGCOUNT" ] then echo "Usage: `basename $0` domain-name" exit $E_WRONGARGS fi
dig +short $1.contacts.abuse.net -c in -t txt # Also try: # dig +nssearch $1 # Tries to find "authoritative name servers" and display SOA records.
# The following also works: # whois -h whois.abuse.net $1 # ^^ ^^^^^^^^^^^^^^^ Specify host. # Can even lookup multiple spammers with this, i.e." # whois -h whois.abuse.net $spamdomain1 $spamdomain2 . . .
# Exercise: # -------- # Expand the functionality of this script #+ so that it automatically e-mails a notification #+ to the responsible ISP's contact address(es). # Hint: use the "mail" command.
exit $?
# spam-lookup.sh chinatietong.com # A known spam domain.
# "crnet_mgr@chinatietong.com" # "crnet_tec@chinatietong.com" # "postmaster@chinatietong.com"
# For a more elaborate version of this script, #+ see the SpamViz home page, http://www.spamviz.net/index.html.
Analyzing a spam domain
#! /bin/bash # is-spammer.sh: Identifying spam domains
# $Id: is-spammer, v 1.4 2004/09/01 19:37:52 mszick Exp $ # Above line is RCS ID info. # # This is a simplified version of the "is_spammer.bash #+ script in the Contributed Scripts appendix.
# is-spammer <domain.name>
# Uses an external program: 'dig' # Tested with version: 9.2.4rc5
# Uses functions. # Uses IFS to parse strings by assignment into arrays. # And even does something useful: checks e-mail blacklists.
# Use the domain.name(s) from the text body: # http://www.good_stuff.spammer.biz/just_ignore_everything_else # ^^^^^^^^^^^ # Or the domain.name(s) from any e-mail address: # Really_Good_Offer@spammer.biz # # as the only argument to this script. #(PS: have your Inet connection running) # # So, to invoke this script in the above two instances: # is-spammer.sh spammer.biz
# Whitespace == :Space:Tab:Line Feed:Carriage Return: WSP_IFS=$'\x20'$'\x09'$'\x0A'$'\x0D'
# No Whitespace == Line Feed:Carriage Return No_WSP=$'\x0A'$'\x0D'
# Field separator for dotted decimal ip addresses ADR_IFS=${No_WSP}'.'
# Get the dns text resource record. # get_txt <error_code> <list_query> get_txt() {
# Parse $1 by assignment at the dots. local -a dns IFS=$ADR_IFS dns=( $1 ) IFS=$WSP_IFS if [ "${dns[0]}" == '127' ] then # See if there is a reason. echo $(dig +short $2 -t txt) fi }
# Get the dns address resource record. # chk_adr <rev_dns> <list_server> chk_adr() { local reply local server local reason
server=${1}${2} reply=$( dig +short ${server} )
# If reply might be an error code . . . if [ ${#reply} -gt 6 ] then reason=$(get_txt ${reply} ${server} ) reason=${reason:-${reply}} fi echo ${reason:-' not blacklisted.'} }
# Need to get the IP address from the name. echo 'Get address of: '$1 ip_adr=$(dig +short $1) dns_reply=${ip_adr:-' no answer '} echo ' Found address: '${dns_reply}
# A valid reply is at least 4 digits plus 3 dots. if [ ${#ip_adr} -gt 6 ] then echo declare query
# Parse by assignment at the dots. declare -a dns IFS=$ADR_IFS dns=( ${ip_adr} ) IFS=$WSP_IFS
# Reorder octets into dns query order. rev_dns="${dns[3]}"'.'"${dns[2]}"'.'"${dns[1]}"'.'"${dns[0]}"'.'
# See: http://www.spamhaus.org (Conservative, well maintained) echo -n 'spamhaus.org says: ' echo $(chk_adr ${rev_dns} 'sbl-xbl.spamhaus.org')
# See: http://ordb.org (Open mail relays) echo -n ' ordb.org says: ' echo $(chk_adr ${rev_dns} 'relays.ordb.org')
# See: http://www.spamcop.net/ (You can report spammers here) echo -n ' spamcop.net says: ' echo $(chk_adr ${rev_dns} 'bl.spamcop.net')
# # # other blacklist operations # # #
# See: http://cbl.abuseat.org. echo -n ' abuseat.org says: ' echo $(chk_adr ${rev_dns} 'cbl.abuseat.org')
# See: http://dsbl.org/usage (Various mail relays) echo echo 'Distributed Server Listings' echo -n ' list.dsbl.org says: ' echo $(chk_adr ${rev_dns} 'list.dsbl.org')
echo -n ' multihop.dsbl.org says: ' echo $(chk_adr ${rev_dns} 'multihop.dsbl.org')
echo -n 'unconfirmed.dsbl.org says: ' echo $(chk_adr ${rev_dns} 'unconfirmed.dsbl.org')
else echo echo 'Could not use that address.' fi
exit 0
# Exercises: # --------
# 1) Check arguments to script, # and exit with appropriate error message if necessary.
# 2) Check if on-line at invocation of script, # and exit with appropriate error message if necessary.
# 3) Substitute generic variables for "hard-coded" BHL domains.
# 4) Set a time-out for the script using the "+time=" option to the 'dig' command.
For a much more elaborate version of the above script, see Example TODO A-28.
Trace the route taken by packets sent to a remote host. This command
works within a LAN, WAN, or over the Internet. The remote host may be
specified by an IP address. The output of this command may be filtered
by grep or sed in a pipe.
bash$ traceroute 81.9.6.2 traceroute to 81.9.6.2 (81.9.6.2), 30 hops max, 38 byte packets 1 tc43.xjbnnbrb.com (136.30.178.8) 191.303 ms 179.400 ms 179.767 ms 2 or0.xjbnnbrb.com (136.30.178.1) 179.536 ms 179.534 ms 169.685 ms 3 192.168.11.101 (192.168.11.101) 189.471 ms 189.556 ms * ...
Broadcast an ICMP ECHO_REQUEST packet to another machine, either on a local or remote network.
bash$ ping localhost PING localhost.localdomain (127.0.0.1) from 127.0.0.1 : 56(84) bytes of data. 64 bytes from localhost.localdomain (127.0.0.1): icmp_seq=0 ttl=255 time=709 usec 64 bytes from localhost.localdomain (127.0.0.1): icmp_seq=1 ttl=255 time=286 usec
--- localhost.localdomain ping statistics --- 2 packets transmitted, 2 packets received, 0% packet loss round-trip min/avg/max/mdev = 0.286/0.497/0.709/0.212 ms
A successful ping returns an exit status of 0. This can be
tested for in a script.
HNAME=news-15.net # Notorious spammer. # HNAME=$HOST # Debug: test for localhost. count=2 # Send only two pings.
if [[ `ping -c $count "$HNAME"` ]] then echo ""$HNAME" still up and broadcasting spam your way." else echo ""$HNAME" seems to be down. Pity." fi
-h option permits
specifying which particular whois server to query. See TODO Example 4-6 and
Example 16-40.Retrieve information about users on a network. Optionally, this
command can display a user's ~/.plan, ~/.project, and
~/.forward files, if present.
bash$ finger Login Name Tty Idle Login Time Office Office Phone bozo Bozo Bozeman tty1 8 Jun 25 16:59 (:0) bozo Bozo Bozeman ttyp0 Jun 25 16:59 (:0.0) bozo Bozo Bozeman ttyp1 Jun 25 17:07 (:0.0)
bash$ finger bozo Login: bozo Name: Bozo Bozeman Directory: /home/bozo Shell: /bin/bash Office: 2355 Clown St., 543-1234 On since Fri Aug 31 20:13 (MST) on tty1 1 hour 38 minutes idle On since Fri Aug 31 20:13 (MST) on pts/0 12 seconds idle On since Fri Aug 31 20:13 (MST) on pts/1 On since Fri Aug 31 20:31 (MST) on pts/2 1 hour 16 minutes idle Mail last read Tue Jul 3 10:08 2007 (MST) No Plan.
Out of security considerations, many networks disable finger and its associated daemon. [1]
finger command.Verify an Internet e-mail address.
This command seems to be missing from newer Linux distros.
sx and rx command set serves to transfer files
to and from a remote host using the xmodem protocol. These are
generally part of a communications package, such as minicom.sz and rz command set serves to transfer files
to and from a remote host using the zmodem protocol. Zmodem has
certain advantages over xmodem, such as faster transmission rate and
resumption of interrupted file transfers. Like sx and
rx, these are generally part of a communications package.ftp session can be automated in a script
(see Example TODO 19-6 and Example A-4).uucp: UNIX to UNIX copy. This is a communications package
for transferring files between UNIX servers. A shell script is an
effective way to handle a uucp command sequence.
Since the advent of the Internet and e-mail, uucp seems to
have faded into obscurity, but it still exists and remains perfectly
workable in situations where an Internet connection is not available
or appropriate. The advantage of uucp is that it is
fault-tolerant, so even if there is a service interruption the copy
operation will resume where it left off when the connection is
restored.
uux: UNIX to UNIX execute. Execute a command on a remote
system. This command is part of the uucp package.
cu: Call Up a remote system and connect as a simple
terminal. It is a sort of dumbed-down version of
telnet. This command is part of the uucp package.
Utility and protocol for connecting to a remote host.
Caution: The telnet protocol contains security holes and
should therefore probably be avoided. Its use within a shell script is
not recommended.
The wget utility noninteractively retrieves or downloads
files from a Web or ftp site. It works well in a script.
wget -p http://www.xyz23.com/file01.html # The -p or --page-requisite option causes wget to fetch all files #+ required to display the specified page.
wget -r ftp://ftp.xyz24.net/~bozo/project_files/ -O $SAVEFILE # The -r option recursively follows and retrieves all links #+ on the specified site.
wget -c ftp://ftp.xyz25.net/bozofiles/filename.tar.bz2 # The -c option lets wget resume an interrupted download. # This works with ftp servers and many HTTP sites.
Getting a stock quote
#!/bin/bash # quote-fetch.sh: Download a stock quote.
E_NOPARAMS=86
if [ -z "$1" ] # Must specify a stock (symbol) to fetch. then echo "Usage: `basename $0` stock-symbol" exit $E_NOPARAMS fi
stock_symbol=$1
file_suffix=.html # Fetches an HTML file, so name it appropriately. URL='http://finance.yahoo.com/q?s=' # Yahoo finance board, with stock query suffix.
# ----------------------------------------------------------- wget -O ${stock_symbol}${file_suffix} "${URL}${stock_symbol}" # -----------------------------------------------------------
# To look up stuff on http://search.yahoo.com: # ----------------------------------------------------------- # URL="http://search.yahoo.com/search?fr=ush-news&p=${query}" # wget -O "$savefilename" "${URL}" # ----------------------------------------------------------- # Saves a list of relevant URLs.
exit $?
# Exercises: # --------- # # 1) Add a test to ensure the user running the script is on-line. # (Hint: parse the output of 'ps -ax' for "ppp" or "connect." # # 2) Modify this script to fetch the local weather report, #+ taking the user's zip code as an argument.
See also Example TODO A-30 and Example A-31.
The lynx Web and file browser can be used inside a script
(with the -dump option) to retrieve a file from a Web or ftp
site noninteractively.
lynx -dump http://www.xyz23.com/file01.html >$SAVEFILE
With the -traversal option, lynx starts at the HTTP
URL specified as an argument, then "crawls" through all links located
on that particular server. Used together with the -crawl
option, outputs page text to a log file.
ssh instead.ssh instead.scp instead.Remote synchronize, updates (synchronizes) files between two different networked machines.
bash$ rsync -a ~/sourcedir/*txt /node1/subdirectory/
Updating FC4
#!/bin/bash # fc4upd.sh
# Script author: Frank Wang. # Slight stylistic modifications by ABS Guide author. # Used in ABS Guide with permission.
# Download Fedora Core 4 update from mirror site using rsync. # Should also work for newer Fedora Cores -- 5, 6, . . . # Only download latest package if multiple versions exist, #+ to save space.
URL=rsync://distro.ibiblio.org/fedora-linux-core/updates/ # URL=rsync://ftp.kddilabs.jp/fedora/core/updates/ # URL=rsync://rsync.planetmirror.com/fedora-linux-core/updates/
DEST=${1:-/var/www/html/fedora/updates/} LOG=/tmp/repo-update-$(/bin/date +%Y-%m-%d).txt PID_FILE=/var/run/${0##*/}.pid
E_RETURN=85 # Something unexpected happened.
# General rsync options # -r: recursive download # -t: reserve time # -v: verbose
OPTS="-rtv --delete-excluded --delete-after --partial"
# rsync include pattern # Leading slash causes absolute path name match. INCLUDE=( "/4/i386/kde-i18n-Chinese*" # ^ ^ # Quoting is necessary to prevent globbing. )
# rsync exclude pattern # Temporarily comment out unwanted pkgs using "#" . . . EXCLUDE=( /1 /2 /3 /testing /4/SRPMS /4/ppc /4/x86_64 /4/i386/debug "/4/i386/kde-i18n-*" "/4/i386/openoffice.org-langpack-*" "/4/i386/*i586.rpm" "/4/i386/GFS-*" "/4/i386/cman-*" "/4/i386/dlm-*" "/4/i386/gnbd-*" "/4/i386/kernel-smp*" # "/4/i386/kernel-xen*" # "/4/i386/xen-*" )
init () { # Let pipe command return possible rsync error, e.g., stalled network. set -o pipefail # Newly introduced in Bash, version 3.
TMP=${TMPDIR:-/tmp}/${0##*/}.$$ # Store refined download list. trap "{ rm -f $TMP 2>/dev/null }" EXIT # Clear temporary file on exit. }
check_pid () { # Check if process exists. if [ -s "$PID_FILE" ]; then echo "PID file exists. Checking ..." PID=$(/bin/egrep -o "^[[:digit:]]+" $PID_FILE) if /bin/ps --pid $PID &>/dev/null; then echo "Process $PID found. ${0##*/} seems to be running!" /usr/bin/logger -t ${0##*/} \ "Process $PID found. ${0##*/} seems to be running!" exit $E_RETURN fi echo "Process $PID not found. Start new process . . ." fi }
# Set overall file update range starting from root or $URL, #+ according to above patterns. set_range () { include= exclude= for p in "${INCLUDE[@]}"; do include="$include --include \"$p\"" done
for p in "${EXCLUDE[@]}"; do exclude="$exclude --exclude \"$p\"" done }
# Retrieve and refine rsync update list. get_list () { echo $$ > $PID_FILE || { echo "Can't write to pid file $PID_FILE" exit $E_RETURN }
echo -n "Retrieving and refining update list . . ."
# Retrieve list -- 'eval' is needed to run rsync as a single command. # $3 and $4 is the date and time of file creation. # $5 is the full package name. previous= pre_file= pre_date=0 eval /bin/nice /usr/bin/rsync \ -r $include $exclude $URL | \ egrep '^dr.x|^-r' | \ awk '{print $3, $4, $5}' | \ sort -k3 | \ { while read line; do # Get seconds since epoch, to filter out obsolete pkgs. cur_date=$(date -d "$(echo $line | awk '{print $1, $2}')" +%s) # echo $cur_date
# Get file name. cur_file=$(echo $line | awk '{print $3}') # echo $cur_file
# Get rpm pkg name from file name, if possible. if [[ $cur_file == *rpm ]]; then pkg_name=$(echo $cur_file | sed -r -e \ 's/(^([^_-]+[_-])+)[[:digit:]]+\..*[_-].*$/\1/') else pkg_name= fi # echo $pkg_name
if [ -z "$pkg_name" ]; then # If not a rpm file, echo $cur_file >> $TMP #+ then append to download list. elif [ "$pkg_name" != "$previous" ]; then # A new pkg found. echo $pre_file >> $TMP # Output latest file. previous=$pkg_name # Save current. pre_date=$cur_date pre_file=$cur_file elif [ "$cur_date" -gt "$pre_date" ]; then # If same pkg, but newer, pre_date=$cur_date #+ then update latest pointer. pre_file=$cur_file fi done echo $pre_file >> $TMP # TMP contains ALL #+ of refined list now. # echo "subshell=$BASH_SUBSHELL"
} # Bracket required here to let final "echo $pre_file >> $TMP" # Remained in the same subshell ( 1 ) with the entire loop.
RET=$? # Get return code of the pipe command.
[ "$RET" -ne 0 ] && { echo "List retrieving failed with code $RET" exit $E_RETURN }
echo "done"; echo }
# Real rsync download part. get_file () {
echo "Downloading..." /bin/nice /usr/bin/rsync \ $OPTS \ --filter "merge,+/ $TMP" \ --exclude '*' \ $URL $DEST \ | /usr/bin/tee $LOG
RET=$?
# --filter merge,+/ is crucial for the intention. # + modifier means include and / means absolute path. # Then sorted list in $TMP will contain ascending dir name and #+ prevent the following --exclude '*' from "shortcutting the circuit."
echo "Done"
rm -f $PID_FILE 2>/dev/null
return $RET }
# ------- # Main init check_pid set_range get_list get_file RET=$? # -------
if [ "$RET" -eq 0 ]; then /usr/bin/logger -t ${0##*/} "Fedora update mirrored successfully." else /usr/bin/logger -t ${0##*/} \ "Fedora update mirrored with failure code: $RET" fi
exit $RET
See also TODO Example A-32.
Note: Using rcp, rsync, and similar utilities with
security implications in a shell script may not be
advisable. Consider, instead, using ssh, scp, or
an expect script.
Secure shell, logs onto a remote host and executes commands
there. This secure replacement for telnet,
rlogin, rcp, and rsh uses identity
authentication and encryption. See its manpage for details.
#!/bin/bash # remote.bash: Using ssh.
# This example by Michael Zick. # Used with permission.
# Presumptions: # ------------ # fd-2 isn't being captured ( '2>/dev/null' ). # ssh/sshd presumes stderr ('2') will display to user. # # sshd is running on your machine. # For any 'standard' distribution, it probably is, #+ and without any funky ssh-keygen having been done.
# Try ssh to your machine from the command-line: # # $ ssh $HOSTNAME # Without extra set-up you'll be asked for your password. # enter password # when done, $ exit # # Did that work? If so, you're ready for more fun.
# Try ssh to your machine as 'root': # # $ ssh -l root $HOSTNAME # When asked for password, enter root's, not yours. # Last login: Tue Aug 10 20:25:49 2004 from localhost.localdomain # Enter 'exit' when done.
# The above gives you an interactive shell. # It is possible for sshd to be set up in a 'single command' mode, #+ but that is beyond the scope of this example. # The only thing to note is that the following will work in #+ 'single command' mode.
# A basic, write stdout (local) command.
ls -l
# Now the same basic command on a remote machine. # Pass a different 'USERNAME' 'HOSTNAME' if desired: USER=${USERNAME:-$(whoami)} HOST=${HOSTNAME:-$(hostname)}
# Now excute the above command-line on the remote host, #+ with all transmissions encrypted.
ssh -l ${USER} ${HOST} " ls -l "
# The expected result is a listing of your username's home #+ directory on the remote machine. # To see any difference, run this script from somewhere #+ other than your home directory.
# In other words, the Bash command is passed as a quoted line #+ to the remote shell, which executes it on the remote machine. # In this case, sshd does ' bash -c "ls -l" ' on your behalf.
# For information on topics such as not having to enter a #+ password/passphrase for every command-line, see #+ man ssh #+ man ssh-keygen #+ man sshd_config.
exit 0
Caution: Within a loop, ssh may cause unexpected
behavior. According to a Usenet post in the comp.unix shell archives,
ssh inherits the loop's stdin. To remedy this, pass
ssh either the -n or -f option.
rcp, copies files
between two different networked machines, but does so using
authentication, and with a security level similar to ssh.This is a utility for terminal-to-terminal communication. It allows
sending lines from your terminal (console or xterm) to that of another
user. The mesg command may, of course, be used to disable write access
to a terminal
Since write is interactive, it would not normally find use in a script.
Send or read e-mail messages.
This stripped-down command-line mail client works fine as a command embedded in a script.
A script that mails itself
#!/bin/sh # self-mailer.sh: Self-mailing script
adr=${1:-`whoami`} # Default to current user, if not specified. # Typing 'self-mailer.sh wiseguy@superdupergenius.com' #+ sends this script to that addressee. # Just 'self-mailer.sh' (no argument) sends the script #+ to the person invoking it, for example, bozo@localhost.localdomain. # # For more on the ${parameter:-default} construct, #+ see the "Parameter Substitution" section #+ of the "Variables Revisited" chapter.
# ============================================================================ cat $0 | mail -s "Script \"`basename $0`\" has mailed itself to you." "$adr" # ============================================================================
# -------------------------------------------- # Greetings from the self-mailing script. # A mischievous person has run this script, #+ which has caused it to mail itself to you. # Apparently, some people have nothing better #+ to do with their time. # --------------------------------------------
echo "At `date`, script \"`basename $0`\" mailed to "$adr"."
exit 0
# Note that the "mailx" command (in "send" mode) may be substituted #+ for "mail" ... but with somewhat different options.
Show mail statistics. This command may be invoked only by root.
root# mailstats Statistics from Tue Jan 1 20:32:08 2008 M msgsfr bytes_from msgsto bytes_to msgsrej msgsdis msgsqur Mailer 4 1682 24118K 0 0K 0 0 0 esmtp 9 212 640K 1894 25131K 0 0 0 local ===================================================================== T 1894 24758K 1894 25131K 0 0 0 C 414 0
sendmail, and is not applicable
to a dial-up POPmail account.