Shell Scripting: Expert Recipes for Linux, Bash and more

Shell Scripting: Expert Recipes for Linux, Bash and more

Steve Parker

Language: English

Pages: 600

ISBN: 1118024486

Format: PDF / Kindle (mobi) / ePub


A compendium of shell scripting recipes that can immediately be used, adjusted, and applied

The shell is the primary way of communicating with the Unix and Linux systems, providing a direct way to program by automating simple-to-intermediate tasks. With this book, Linux expert Steve Parker shares a collection of shell scripting recipes that can be used as is or easily modified for a variety of environments or situations. The book covers shell programming, with a focus on Linux and the Bash shell; it provides credible, real-world relevance, as well as providing the flexible tools to get started immediately.

  • Shares a collection of helpful shell scripting recipes that can immediately be used for various of real-world challenges
  • Features recipes for system tools, shell features, and systems administration
  • Provides a host of plug and play recipes for to immediately apply and easily modify so the wheel doesn't have to be reinvented with each challenge faced

Come out of your shell and dive into this collection of tried and tested shell scripting recipes that you can start using right away!

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simpler model suffices. The shell is somewhat unique in the syntax for using variables. Many (such as Perl, PHP, and others) use a dollar sign prefi x whenever the variable is referred to; others (such as Java or C) use no specific markup to identify a variable; the context is enough to make it clear that the code is referring to a variable. 34 ❘ chapter 3 VariabLes Sometimes you need a dollar sign to reference a variable (echo $variable) and sometimes you need to not have a dollar sign

characters. This is expressed as +(a-z). You can also use [:alpha:] in place of (a-z) so this example uses both. The extglob patterns look a lot like normal shell filename expansion patterns, but the ( and ) would be illegal in normal filename expansion. shopt -s extglob ls /dev/sd+([a-z]) for disk in /dev/sd+([[:alpha:]]) do fdisk -l $disk done You could also use the GLOBIGNORE variable to fi nd just the disks without the partitions. You can set GLOBIGNORE to a pattern that will be cut from

out of this loop, In the number loop - 3 Press b to break out of this loop: 2 to break out totally: z 2 to break out totally: z 2 to break out totally: 1 z 2 to break out totally: z 2 to break out totally: z 2 to break out totally: 1 z Now in the letter loop... 3 a Press 1 to break out of this loop, 2 to break out totally: z Now in the letter loop... 3 b Press 1 to break out of this loop, 2 to break out totally: z Now in the letter loop... 3 c Press 1 to break out of this loop, 2 to break out

redhat-nics.sh 164 ❘ chapter 8 fUncTions and Libraries Because different Linux distributions use different mechanisms for configuring networks, this script does not work on a system that doesn’t use the Red Hat style of network configuration. A good technique is to check for the existence of /etc/redhat-release, which should exist on any Red Hat or derivative system, such as CentOS or Oracle Linux. debian$ ./redhat-nics.sh cd: 29: can’t cd to /etc/sysconfig/network-scripts This does not seem

or even more, the flexibility of the system is increased with every added tool. In the case of more, this is actually more tricky than it seems; first it has to find out how many columns and rows are available. Again, there is a set of tools that combine to provide this information. In this way, every tool in the chain can be used by the other tools. Unix  ❘  5 Also this system means that you do not have to learn how each individual utility implements its “word count” feature. There are a

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