UNIX is an extremely popular platform for deploying server software partly because of its security and stability, but also because it has a rich set of command line and scripting tools. Programmers use these tools for manipulating the file system, processing log files, and generally automating as much as possible.
If you want to be a serious server developer, you will need to have a certain facility with a number of UNIX tools; about 15. You will start to see similarities among them, particularly regular expressions, and soon you will feel very comfortable. Combining the simple commands, you can build very powerful tools very quickly--much faster than you could build the equivalent functionality in C or Java, for example.
This lecture takes you through the basic commands and then shows you how to combine them in simple patterns or idioms to provide sophisticated functionality like histogramming. This lecture assumes you know what a shell is and that you have some basic familiarity with UNIX.
[By the way, this page gets a lot of attention on the net and unfortunately I get mail from lots of people that have better solutions or stuff I should add. I'm only showing what I've learned from watching good UNIX people so I am not saying these tips are the optimal solutions. I'd make a pretty ignorant sys admin.]
Everything is a stream
The first thing you need to know is that UNIX is based upon the idea of a stream. Everything is a stream, or appears to be. Device drivers look like streams, terminals look like streams, processes communicate via streams, etc... The input and output of a program are streams that you can redirect into a device, a file, or another program.
Here is an example device, the null device, that lets you throw output away. For example, you might want to run a program but ignore the output.
$ ls > /dev/null # ignore output of ls
where "# ignore output of ls" is a comment.
Most of the commands covered in this lecture process stdin and send results to stdout. In this manner, you can incrementally process a data stream by hooking the output of one tool to the input of another via a pipe. For example, the following piped sequence prints the number of files in the current directory modified in August.
$ ls -l | grep Aug | wc -l
Imagine how long it would take you to write the equivalent C or Java program. You can become an extremely productive UNIX programmer if you learn to combine the simple command-line tools. Even when programming on a PC, I use MKS's UNIX shell and command library to make it look like a UNIX box. Worth the cash.
Getting help
If you need to know about a command, ask for the "man" page. For example, to find out about the ls command, type
$ man ls
LS(1) System General Commands Manual LS(1)
NAME
ls - list directory contents
SYNOPSIS
ls [-ACFLRSTWacdfgiklnoqrstux1] [file ...]
DESCRIPTION
For each operand that names a file of a type other than directory, ls
...
You will get a summary of the command and any arguments.
If you cannot remember the command's name, try using apropos which finds commands and library routines related to that word. For example, to find out how to do checksums, type
$ apropos checksum
cksum(1), sum(1) - display file checksums and block counts
md5(1) - calculate a message-digest fingerprint (checksum) for a file
Special Directories and files
A shortcut for you home directory, /home/username, is ~username. For example, ~parrt is my home directory,/home/parrt.
When you are using the shell, there is the notion of current directory. The dot '.' character is a shorthand for the current directory and '..' is a shorthand for the directory above the current. So to access file test in the current directory, ./test is the same as plain test. If test is a directory above, use ../test.
/ is the root directory; there is no drive specification in UNIX.
The .bash_profile file is very important as it is how your shell session is initialized including your ever-importantCLASSPATH environment variable. Your bash shell initialization file is ~username/.bash_profile and has set up code like the following:
Typically, you will go in and set your CLASSPATH so that you don't have to set it all the time.
export CLASSPATH=".:/home/public/cs601/junit.jar"
The export means that the assignment to CLASSPATH is visible to all child processes (that is, visible to all programs you run from the shell).
The basics
cd
Changing a directory is done with cd dir where dir can be "." or ".." to move to current directory (do nothing) or go up a directory.
ls
Display files in a directory with ls. The -l option is used to display details of the files:
total 9592
-rw-r--r-- 1 parrt staff 5600 Aug 19 2005 C-Java-relationship.html
...
drwxr-xr-x 13 parrt staff 442 Oct 19 2005 sessions
-rw-r--r-- 1 parrt staff 2488 Oct 19 2005 sessions.html
...
"staff" is parrt's group.
If you want to see hidden files (those starting with "."), use "-a".
Combinations are possible: use "ls -la" to see details of all files including hidden ones.
displaying files
There are 4 useful ways to display the contents or portions of a file. The first is the very commonly used commandcat. For example, to display my list of object-oriented keywords used in this course, type:
$ cat /home/public/cs601/oo.keywords.txt
If a file is really big, you will probably want to use more, which spits the file out in screen-size chunks.
If you only want to see the first few lines of a file or the last few lines use head and tail.
$ head /var/log/mail.log
$ tail /var/log/mail.log
You can specify a number as an argument to get a specific number of lines:
$ head -30 /var/log/mail.log
The most useful incantation of tail prints the last few lines of a file and then waits, printing new lines as they are appended to the file. This is great for watching a log file:
$ tail -f /var/log/mail.log
If you need to know how many characters, words, or lines are in a file, use wc:
$ wc /var/log/mail.log
164 2916 37896 /var/log/mail.log
Where the numbers are, in order, lines, words, then characters. For clarity, you can use wc -l to print just the number of lines.
pushd, popd
Instead of cd you can use pushd to save the current dir and then automatically cd to the specified directory. For example,
$ pwd
/Users/parrt
$ pushd /tmp
/tmp ~
$ pwd
/tmp
$ popd
~
$ pwd
/Users/parrt
top
To watch a dynamic display of the processes on your box in action, use top.
ps
To print out (wide display) all processes running on a box, use ps auxwww.
chmod
To change the privileges of a file or directory, use chmod. The privileges are 3 digit octal words with 3 bits per digit: rwxrwxrwx where the first digit is for the file owner, the 2nd for the group, and 3rd for anybody. 644 is a common word value file which means 110100100 or rw-r--r--. When you do ls -l you will see these bits. 755 is a common word value for directories: rwxr-xr-x where directories need to be executable for cd to be able to enter that dir. 755 is a shorthand for the more readable argument u=rwx,go=rx. u is user, g is group, o is other.
Use chmod -R for recursively applying to all the dirs below the argument as well.
Searching streams
One of the most useful tools available on UNIX and the one you may use the most is grep. This tool matches regular expressions (which includes simple words) and prints matching lines to stdout.
The simplest incantation looks for a particular character sequence in a set of files. Here is an example that looks for any reference to System in the java files in the current directory.
You may find the dot '.' regular expression useful. It matches any single character but is typically combined with the star, which matches zero or more of the preceding item. Be careful to enclose the expression in single quotes so the command-line expansion doesn't modify the argument. The following example, looks for references to any a forum page in a server log file:
$ grep '/forum/.*' /home/public/cs601/unix/access.log
or equivalently:
$ cat /home/public/cs601/unix/access.log | grep '/forum/.*'
The second form is useful when you want to process a collection of files as a single stream as in:
cat /home/public/cs601/unix/access*.log | grep '/forum/.*'
If you need to look for a string at the beginning of a line, use caret '^':
$ grep '^195.77.105.200' /home/public/cs601/unix/access*.log
This finds all lines in all access logs that begin with IP address 195.77.105.200.
If you would like to invert the pattern matching to find lines that do not match a pattern, use -v. Here is an example that finds references to non image GETs in a log file:
$ cat /home/public/cs601/unix/access.log | grep -v '/images'
Now imagine that you have an http log file and you would like to filter out page requests made by nonhuman spiders. If you have a file called spider.IPs, you can find all nonspider page views via:
$ cat /home/public/cs601/unix/access.log | grep -v -f /tmp/spider.IPs
Finally, to ignore the case of the input stream, use -i.
Translating streams
Morphing a text stream is a fundamental UNIX operation. PERL is a good tool for this, but since I don't like PERL I stick with three tools: tr, sed, and awk. PERL and these tools are line-by-line tools in that they operate well only on patterns fully contained within a single line. If you need to process more complicated patterns like XML or you need to parse a programming language, use a context-free grammar tool like ANTLR.
tr
For manipulating whitespace, you will find tr very useful.
If you have columns of data separated by spaces and you would like the columns to collapse so there is a single column of data, tell tr to replace space with newline tr ' ' '\n'. Consider input file /home/public/cs601/unix/names:
jim scott mike
bill randy tom
To get all those names in a column, use
$ cat /home/public/cs601/unix/names | tr ' ' '\n'
If you would like to collapse all sequences of spaces into one single space, use tr -s ' '.
To convert a PC file to UNIX, you have to get rid of the '\r' characters. Use tr -d '\r'.
sed
If dropping or translating single characters is not enough, you can use sed (stream editor) to replace or delete text chunks matched by regular expressions. For example, to delete all references to word scott in the names file from above, use
$ cat /home/public/cs601/unix/names | sed 's/scott//'
which substitutes scott for nothing. If there are multiple references to scott on a single line, use the g suffix to indicate "global" on that line otherwise only the first occurrence will be removed:
If you would like to replace references to view.jsp with index.jsp, use
$ ... | sed 's/view.jsp/index.jsp/'
If you want any .asp file converted to .jsp, you must match the file name with a regular expression and refer to it via \1:
$ ... | sed 's/\(.*\).asp/\1.jsp/'
The \(...\) grouping collects text that you can refer to with \1.
If you want to kill everything from the ',' character to end of line, use the end-of-line marker $:
$ ... | sed 's/,.*$//' # kill from comma to end of line
awk
When you need to work with columns of data or execute a little bit of code for each line matching a pattern, useawk. awk programs are pattern-action pairs. While some awk programs are complicated enough to require a separate file containing the program, you can do some amazing things using an argument on the command-line.
awk thinks input lines are broken up into fields (i.e., columns) separate by whitespace. Fields are referenced in an action via $1, $2, ... while $0 refers to the entire input line.
A pattern-action pair looks like:
If you omit the pattern, the action is executed for each input line. Omitting the action means print the line. You can separate the pairs by newline or semicolon.
Consider input
aasghar Asghar, Ali
wchen Chen, Wei
zchen Chen, Zhen-Jian
If you want a list of login names, ask awk to print the first column:
$ cat /home/public/cs601/unix/emails.txt | awk '{print $1;}'
If you want to convert the login names to email addresses, use the printf C-lookalike function:
$ cat /home/public/cs601/unix/emails.txt | awk '{printf("%s@cs.usfca.edu,",$1);}'
Because of the missing \n in the printf string, you'll see the output all on one line ready for pasting into a mail program:
aasghar@cs.usfca.edu,wchen@cs.usfca.edu,zchen@cs.usfca.edu
You might also want to reorder columns of data. To print firstname, lastname, you might try:
$ cat /home/public/cs601/unix/emails.txt | awk '{printf("%s %s\n", $3, $2);}'
but you'll notice that the comma is still there as it is part of the column:
Ali Asghar,
Wei Chen,
Zhen-Jian Chen,
You need to pipe the output thru tr (or sed) to strip the comma:
$ cat /home/public/cs601/unix/emails.txt | \
awk '{printf("%s %s\n", $3, $2);}' | \
tr -d ','
Then you will see:
Ali Asghar
Wei Chen
Zhen-Jian Chen
You can also use awk to examine the value of content. To sum up the first column of the following data (in file/home/public/cs601/unix/coffee):
use the following simple command:
$ awk '{n+=$1;} ; END {print n;}' < /home/public/cs601/unix/coffee
where END is a special pattern that means "after processing the stream."
If you want to filter or sum all values less than or equal to, say 3, use an if statement:
$ awk '{if ($1<=3) n+=$1;} END {print n;}' < /home/public/cs601/unix/coffee
In this case, you will see output 5 (3+2);
Using awk to grab a particular column is very common when processing log files. Consider a http://www.jguru.compage view log file, /home/public/cs601/unix/pageview-20021022.log, that are of the form:
date-stamp(thread-name): userID-or-IPaddr URL site-section
So, the data looks like this:
20021022_00.00.04(tcpConnection-80-3019): 203.6.152.30 /faq/subtopic.jsp?topicID=472&page=2 FAQs
20021022_00.00.07(tcpConnection-80-2981): 995134 /index.jsp Home
20021022_00.00.08(tcpConnection-80-2901): 66.67.34.44 /faq/subtopic.jsp?topicID=364 FAQs
20021022_00.00.12(tcpConnection-80-3003): 217.65.96.13 /faq/view.jsp?EID=736437 FAQs
20021022_00.00.13(tcpConnection-80-3019): 203.124.210.98 /faq/topicindex.jsp?topic=JSP FAQs/JSP
20021022_00.00.15(tcpConnection-80-2988): 202.56.231.154 /faq/index.jsp FAQs
20021022_00.00.19(tcpConnection-80-2976): 66.67.34.44 /faq/view.jsp?EID=225150 FAQs
220021022_00.00.21(tcpConnection-80-2974): 143.89.192.5 /forums/most_active.jsp?topic=EJB Forums/EJB
20021022_00.00.21(tcpConnection-80-2996): 193.108.239.34 /guru/edit_account.jsp Guru
20021022_00.00.21(tcpConnection-80-2996): 193.108.239.34 /misc/login.jsp Misc
...
When a user is logged in, the log file has their user ID rather than their IP address.
Here is how you get a list of URLs that people view on say October 22, 2002:
$ awk '{print $3;}' < /home/public/cs601/unix/pageview-20021022.log
/faq/subtopic.jsp?topicID=472&page=2
/index.jsp
/faq/subtopic.jsp?topicID=364
/faq/view.jsp?EID=736437
/faq/topicindex.jsp?topic=JSP
/faq/index.jsp
/faq/view.jsp?EID=225150
/forums/most_active.jsp?topic=EJB
/guru/edit_account.jsp
/misc/login.jsp
...
If you want to count how many page views there were that day that were not processing pages (my processing pages are all of the form process_xxx), pipe the results through grep and wc:
$ awk '{print $3;}' < /home/public/cs601/unix/pageview-20021022.log | \
grep -v process | \
wc -l
67850
If you want a unique list of URLs, you can sort the output and then use uniq:
$ awk '{print $3;}' < /home/public/cs601/unix/pageview-20021022.log | \
sort | \
uniq
uniq just collapses all repeated lines into a single line--that is why you must sort the output first. You'll get output like:
/article/index.jsp
/article/index.jsp?page=1
/article/index.jsp?page=10
/article/index.jsp?page=2
...
Tarballs
Note: The name comes from a similar word, hairball (stuff that cats throw up), I'm pretty sure.
To collect a bunch of files and directories together, use tar. For example, to tar up your entire home directory and put the tarball into /tmp, do this
$ cd ~parrt
$ cd .. # go one dir above dir you want to tar
$ tar cvf /tmp/parrt.backup.tar parrt
By convention, use .tar as the extension. To untar this file use
$ cd /tmp
$ tar xvf parrt.backup.tar
tar untars things in the current directory!
After running the untar, you will find a new directory, /tmp/parrt, that is a copy of your home directory. Note that the way you tar things up dictates the directory structure when untarred. The fact that I mentioned parrt in the tar creation means that I'll have that dir when untarred. In contrast, the following will also make a copy of my home directory, but without having a parrt root dir:
$ cd ~parrt
$ tar cvf /tmp/parrt.backup.tar *
It is a good idea to tar things up with a root directory so that when you untar you don't generate a million files in the current directly. To see what's in a tarball, use
$ tar tvf /tmp/parrt.backup.tar
Most of the time you can save space by using the z argument. The tarball will then be gzip'd and you should use file extension .tar.gz:
$ cd ~parrt
$ cd .. # go one dir above dir you want to tar
$ tar cvfz /tmp/parrt.backup.tar.gz parrt
Unzipping requires the z argument also:
$ cd /tmp
$ tar xvfz parrt.backup.tar.gz
If you have a big file to compress, use gzip:
After execution, your file will have been renamed bigfile.gz. To uncompress, use
To display a text file that is currently gzip'd, use zcat:
Moving files between machines
rsync
When you need to have a directory on one machine mirrored on another machine, use rsync. It compares all the files in a directory subtree and copies over any that have changed to the mirrored directory on the other machine. For example, here is how you could "pull" all logs files from livebox.jguru.com to the box from which you execute thersync command:
$ hostname
jazz.jguru.com
$ rsync -rabz -e ssh -v 'parrt@livebox.jguru.com:/var/log/jguru/*' \
/backup/web/logs
rsync will delete or truncate files to ensure the files stay the same. This is bad if you erase a file by mistake--it will wipe out your backup file. Add an argument called --suffix to tell rsync to make a copy of any existing file before it overwrites it:
$ hostname
jazz.jguru.com
$ rsync -rabz -e ssh -v --suffix .rsync_`date '+%Y%m%d'` \
'parrt@livebox.jguru.com:/var/log/jguru/*' /backup/web/logs
where `date '+%Y%m%d'` (in reverse single quotes) means "execute this date command".
To exclude certain patterns from the sync, use --exclude:
$ rsync -rabz --exclude=entitymanager/ --suffix .rsync_`date '+%Y%m%d'` \
-e ssh -v 'parrt@livebox.jguru.com:/var/log/jguru/*' /backup/web/logs
scp
To copy a file or directory manually, use scp:
$ scp lecture.html parrt@nexus.cs.usfca.edu:~parrt/lectures
Just like cp, use -r to copy a directory recursively.
Miscellaneous
find
Most GUIs for Linux or PCs have a search facility, but from the command-line you can use find. To find all files named .p4 starting in directory ~/antlr/depot/projects, use:
$ find ~/antlr/depot/projects -name '.p4'
The default "action" is to -print.
You can specify a regular expression to match. For example, to look under your home directory for any xml files, use:
$ find ~ -name '*.xml' -print
Note the use of the single quotes to prevent command-line expansion--you want the '*' to go to the findcommand.
You can execute a command for every file or directory found that matches a name. For example, do delete all xml files, do this:
$ find ~ -name '*.xml' -exec rm {} \;
where "{}" stands for "current file that matches". The end of the command must be terminated with ';' but because of the command-line expansion, you'll need to escape the ';'.
You can also specify time information in your query. Here is a shell script that uses find to delete all files older than 14 days.
#!/bin/sh
BACKUP_DIR=/var/data/backup
# number of days to keep backups
AGE=14 # days
AGE_MINS=$[ $AGE * 60 * 24 ]
# delete dirs/files
find $BACKUP_DIR/* -cmin +$AGE_MINS -type d -exec rm -rf {} \;
fuser
If you want to know who is using a port such as HTTP (80), use fuser. You must be root to use this:
$ sudo /sbin/fuser -n tcp 80
80/tcp: 13476 13477 13478 13479 13480
13481 13482 13483 13484 13486 13487 13489 13490 13491
13492 13493 13495 13496 13497 13498 13499 13500 13501 13608
The output indicates the list of processes associated with that port.
whereis
Sometimes you want to use a command but it's not in your PATH and you can't remember where it is. Use whereis to look in standard unix locations for the command.
$ whereis fuser
fuser: /sbin/fuser /usr/man/man1/fuser.1 /usr/man/man1/fuser.1.gz
$ whereis ls
ls: /bin/ls /usr/man/man1/ls.1 /usr/man/man1/ls.1.gz
whereis also shows man pages.
which
Sometimes you might be executing the wrong version of a command and you want to know which version of the command your PATH indicates should be run. Use which to ask:
$ which ls
alias ls='ls --color=tty'
/bin/ls
$ which java
/usr/local/java/bin/java
If nothing is found in your path, you'll see:
$ which fuser
/usr/bin/which: no fuser in (/usr/local/bin:/usr/local/java/bin:/usr/local/bin:/bin:/usr/bin:/usr/X11R6/bin:/usr/X11R6/bin:/home/parrt/bin)
kill
To send a signal to a process, use kill. Typically you'll want to just say kill pid where pid can be found from psor top (see below).
Use kill -9 pid when you can't get the process to die; this means kill it with "extreme prejudice".
traceroute
If you are having trouble getting to a site, use traceroute to watch the sequence of hops used to get to a site:
$ /usr/sbin/traceroute www.cnn.com
1 65.219.20.145 (65.219.20.145) 2.348 ms 1.87 ms 1.814 ms
2 loopback0.gw5.sfo4.alter.net (137.39.11.23) 3.667 ms 3.741 ms 3.695 ms
3 160.atm3-0.xr1.sfo4.alter.net (152.63.51.190) 3.855 ms 3.825 ms 3.993 ms
...
What is my IP address?
Under the eth0 interface, you'll see the inet addr:
eth0 Link encap:Ethernet HWaddr 00:10:DC:58:B1:F0
inet addr:138.202.170.4 Bcast:138.202.170.255 Mask:255.255.255.0
...
Useful combinations
How to kill a set of processes
If you want to kill all java processes running for parrt, you can either run killall java if you are parrt or generate a "kill" script via:
$ ps auxwww|grep java|grep parrt|awk '{print "kill -9 ",$2;}' > /tmp/killparrt
$ bash /tmp/killparrt # run resulting script
The /tmp/killparrt file would look something like:
kill -9 1021
kill -9 1023
kill -9 1024
Note: you can also do this common task with:
Please be aware that this is linux specific; i'm told that it will kill all processing on UNIXen like Solaris!
How to make a histogram
A histogram is set of count, value pairs indicating how often the value occurs. The basic operation will be to sort, then count how many values occur in a row and then reverse sort so that the value with the highest count is at the top of the report.
$ ... | sort |uniq -c|sort -r -n
Note that sort sorts on the whole line, but the first column is obviously significant just as the first letter in someone's last name significantly positions their name in a sorted list.
uniq -c collapses all repeated sequences of values but prints the number of occurrences in front of the value. Recall the previous sorting:
$ awk '{print $3;}' < /home/public/cs601/unix/pageview-20021022.log | \
sort | \
uniq
/article/index.jsp
/article/index.jsp?page=1
/article/index.jsp?page=10
/article/index.jsp?page=2
...
Now add -c to uniq:
$ awk '{print $3;}' < /home/public/cs601/unix/pageview-20021022.log | \
sort | \
uniq -c
623 /article/index.jsp
6 /article/index.jsp?page=1
10 /article/index.jsp?page=10
109 /article/index.jsp?page=2
...
Now all you have to do is reverse sort the lines according to the first column numerically.
$ awk '{print $3;}' < /home/public/cs601/unix/pageview-20021022.log | \
sort | \
uniq -c | \
sort -r -n
6170 /index.jsp
2916 /search/results.jsp
1397 /faq/index.jsp
1018 /forums/index.jsp
884 /faq/home.jsp?topic=Tomcat
...
In practice, you might want to get a histogram that has been "despidered" and only has faq related views. You can filter out all page view lines associated with spider IPs and filter in only faq lines:
$ grep -v -f /tmp/spider.IPs /home/public/cs601/unix/pageview-20021022.log | \
awk '{print $3;}'| \
grep '/faq' | \
sort | \
uniq -c | \
sort -r -n
1397 /faq/index.jsp
884 /faq/home.jsp?topic=Tomcat
525 /faq/home.jsp?topic=Struts
501 /faq/home.jsp?topic=JSP
423 /faq/home.jsp?topic=EJB
...
If you want to only see despidered faq pages that were referenced more than 500 times, add an awk command to the end.
$ grep -v -f /tmp/spider.IPs /home/public/cs601/unix/pageview-20021022.log | \
awk '{print $3;}'| \
grep '/faq' | \
sort | \
uniq -c | \
sort -r -n | \
awk '{if ($1>500) print $0;}'
1397 /faq/index.jsp
884 /faq/home.jsp?topic=Tomcat
525 /faq/home.jsp?topic=Struts
501 /faq/home.jsp?topic=JSP
Generating Java class hierarchy diagrams
A student asked if I knew of a program that generated class hierarchy diagrams. I said "no", but then realized we don't need one. Here's the one liner to do it:
# pulls out superclass and class as $5 and $3:
# public class A extends B ...
# only works for public classes and usual formatting
cat *.java | grep 'public class' $1 | \
awk 'BEGIN {print "digraph foo {";} {print $5 "->" $3;} END {print "}"}'
It generates DOT format graph files. Try it. It's amazing. Works for most cases. Output looks like:
digraph foo {
antlr.CharScanner->JavaLexer
antlr.LLkParser->Mantra
->TestLexer
}
Generating scripts and programs
I like to automate as much as possible. Sometimes that means writing a program that generates another program or script.
Processing mail files
I wanted to get a sequence of SQL commands that would update our database whenever someone's email bounced. Processing the mail file is pretty easy since you can look for the error code followed by the email address. A bounced email looks like:
From MAILER-DAEMON@localhost.localdomain Wed Jan 9 17:32:33 2002
Return-Path: <>
Received: from web.jguru.com (web.jguru.com [64.49.216.133])
by localhost.localdomain (8.9.3/8.9.3) with ESMTP id RAA18767
for ; Wed, 9 Jan 2002 17:32:32 -0800
Received: from localhost (localhost)
by web.jguru.com (8.11.6/8.11.6) id g0A1W2o02285;
Wed, 9 Jan 2002 17:32:02 -0800
Date: Wed, 9 Jan 2002 17:32:02 -0800
From: Mail Delivery Subsystem
Message-Id: <200201100132.g0a1w2o02285@web.jguru.com>
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Subject: Returned mail: see transcript for details
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The original message was received at Wed, 9 Jan 2002 17:32:02 -0800
from localhost [127.0.0.1]
----- The following addresses had permanent fatal errors -----
(reason: 550 Host unknown)
----- Transcript of session follows -----
550 5.1.2 ... Host unknown (Name server: intheneck.com: host not found)
...
Notice the SMTP 550 error message. Look for that at the start of a line then kill the angle brackets, remove the ...and use awk to print out the SQL:
# This script works on one email or a file full of other emails
# since it just looks for the SMTP 550 or 554 results and then
# converts them to SQL commands.
grep -E '^(550|554)' | \
sed 's/[<>]//g' | \
sed 's/\.\.\.//' | \
awk "{printf(\"UPDATE PERSON SET bounce=1 WHERE email='%s';\n\",\$3);}" >> bounces.sql
I have to escape the $3 because it means something to the surround bash shell script and I want awk to see the dollar sign.
Generating getter/setters
#!/bin/bash
# From a type and name (plus firstlettercap version),
# generate a Java getter and setter
#
# Example: getter.setter String name Name
#
TYPE=$1
NAME=$2
UPPER_NAME=$3
echo "public $TYPE get$UPPER_NAME() {"
echo " return $NAME;"
echo "}"
echo
echo "void set$UPPER_NAME($TYPE $NAME) {"
echo " this.$NAME = $NAME;"
echo "}"
echo
Have I been hacked?
Failed logins: /var/log/messages
last, w, uptime
/etc/passwd changed?
fuser for ports
portscans in server report
weird processing hogging CPU?
Now that there is a java browser plugin and a working wine for 64-bit on the Ubuntu repositories, there is not much holding back 64-bit Linux on the desktop. Maybe the only thing missing is the Adobe Flash player. Most of the time Flash is just annoying, nevertheless sometimes needed. Luckily, there is now a Flash Player release for 64-bit Linux (however, still 
. (NB: The screenshot is from a previous release, however the actual binary *is* the latest. You should consider using 
Post-install configuration in brief
Disposable razor blades represents every business person's dream business model: The razor itself sells for cheap, but the blades—which you need to regularly refill—cost an arm and a leg. Turns out, however, that you can do a whole lot to make those blades last longer. Next time your blade's getting dull, try 