Linux System Administration Recipes A Problem-Solution Approach

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CHAPTER 9 ■ WORKING WITH TEXT IN FILES■ Note If you find digraphs annoying (if you regularly have to backspace to correct single characters, you mayend up inserting them by accident), type :unset digraphs in command mode (or add unset digraphs to your~/.vimrc file), and use the following:Ctrl-K char1 char2instead of the following to enter digraphs:char1 backspace char2This method is always available, even when digraphs aren’t set.9-6. Getting Readable Text from BinariesSometimes it can be necessary to see whether you can extract useful string (text) data from binary files. Agood sign that you have a binary file is when you try to cat it and you get a warning that it may be abinary file, although not all systems give you this warning. (Debian lenny doesn’t, but current Ubuntudoes.) If you go ahead with the cat, you’ll get a screenful of gibberish.■ Note If your terminal does get scrambled, type one of these, even if you can’t see what you’re typing:setterm –resetecho [Ctrl-V] [Ctrl-O]This sort of terminal scrambling does seem to be less common than it used to be. You can also use cat -v to getbetter output from binary files.One case may be if you want to get text information out of a proprietary file format. In some cases,your best bet may be to open it in open source software that reads the file format (such asOpenOffice.org for Word documents). However, this can be slow if all you need is text data.For Word documents, the utility antiword (Debian/Ubuntu package antiword, installed with sudoapt-get install antiword) is good:antiword file.doc | less200Download at WoweBook.Com
CHAPTER 9 ■ WORKING WITH TEXT IN FILESIf you want to save it to a file, use this:antiword file.doc > file.txtThat’s no good if you’re looking at something like information from a crash file or a core dump.You may just be able to eyeball it, using cat or a text editor, but this is tough on the eyes.od -c filenameThis will convert bytes to ASCII characters wherever possible, but this is rarely terribly useful,unfortunately. strings is more likely to be helpful. It grabs any ASCII strings it can out of the file it’spointed at.strings filename | lessFor example, you may also be in the position of encountering a random binary file and trying towork out where it came from and what it is or does. Getting any readable text information out of thebinary can be helpful here. If you’re very lucky, you might get help information out of it (try strings/bin/ls | less, and note the help information near the end of the output). To simplify this a bit, youcan pipe the output of strings through grep to look for something specific:> strings /bin/ls | grep -A 5 -n Usage522: Usage: %s [OPTION]... [FILE]...523: List information about the FILEs (the current directory by default).524: Sort entries alphabetically if none of -cftuvSUX nor --sort.525: Mandatory arguments to long options are mandatory for short options too.526: -a, --all do not ignore entries starting with .527: -A, --almost-all do not list implied . and ..The -A 5 option to grep gives five lines of context after the match is found; -n prints the line number.For example, it’s very useful to quickly find out which libraries a particular binary needs:$ strings /usr/bin/latex | grep lib | grep '\.so'The grep '\.so' part is there to restrict the grep lib returns to only those lines that refer toparticular binaries (lib*.so.*) rather than also getting lines such as the error lines from libpng that arereturned on my system! The \ is needed to treat the . as a literal rather than as meaning “any character.”201Download at WoweBook.Com
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Contents■About the Author .......
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■ CONTENTS3-7. Writing a Nagios P
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■ CONTENTS■Chapter 8: Using the
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■ CONTENTSAbout the Author■Juli
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■ CONTENTSAcknowledgmentsMany tha
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■ CONTENTSIntroductionThis book i
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■ INTRODUCTIONDownloading the Cod
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C H A P T E R 1■ ■ ■Saving Yo
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CHAPTER 1 ■ SAVING YOURSELF EFFOR
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C H A P T E R 2■ ■ ■Centraliz
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CHAPTER 2 ■ CENTRALIZING YOUR NET
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C H A P T E R 3■ ■ ■Monitorin
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CHAPTER 3 ■ MONITORING AND UPDATI
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C H A P T E R 4■ ■ ■Taking Ba
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CHAPTER 4 ■ TAKING BACKUPS AND MA
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C H A P T E R 5■ ■ ■Working w
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CHAPTER 5 ■ WORKING WITH FILESYST
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C H A P T E R 6■ ■ ■Securing
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CHAPTER 6 ■ SECURING YOUR SYSTEMS
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Page 191 and 192: C H A P T E R 8■ ■ ■Making Be
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Page 223 and 224: C H A P T E R 10■ ■ ■Things G
Page 225 and 226: CHAPTER 10 ■ THINGS GO IN, THINGS
Page 233 and 234: C H A P T E R 11■ ■ ■Tracking
Page 235 and 236: CHAPTER 11 ■ TRACKING DOWN BUGSTh
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Page 251 and 252: C H A P T E R 12■ ■ ■Managing
Page 253 and 254: CHAPTER 12 ■ MANAGING TIME AND PE
Page 267 and 268: APPENDIX■ ■ ■Perl TipsSee rec
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APPENDIX ■ PERL TIPSPerl Syntax N
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■ ■ ■Index■Symbols$CDPATH,
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■ INDEXenscript option (printing)
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■ INDEX■NNagiosadding hosts to,
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■ INDEXsyslogcentralized logging
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