Bash Shell Scripting/How To Read

~ $ echo "Hello World!" Hello World! ~ $

(1) It's ideal to practice Bash while reading

You will probably find this book most useful if you have a Bash command-line open in another window while you are going through it. You may want to try out some of the examples; but more important is to try things out that aren't just copied from the book. If you think something probably works a certain way, test out your expectations! Except where noted otherwise, the examples in this book do not require any special privileges or permissions, and do not require any software aside from Bash itself and very common utilities that are generally found on any system where Bash is.

(2) Try consulting documentation for unknown commands

When you are experimenting, you will likely find it helpful to consult the documentation for various commands. For commands that are built into Bash, you can use the built-in help command; for example, help echo will "print" (that is, display) information about the built-in echo command. Try typing echo "Hello World!" and the output will be Hello World!. Therefore your echo is used for an output statement ( same as character cout>>"Hello World!" in c++). For external programs, it is likely that their manual pages are installed on your system, in which case you can view them via the man ("manual") command; for example, for information about the cp ("copy") command, you can type man cp. Additionally, most programs, when run with the argument --help, will print some help information; for example, cp --help gives almost as much information as man cp. (With many programs, however, the --help approach does not give anywhere near as much information as the man approach.)

(3) Warning against blindly entering commands

A word of caution: this book is part of a wiki, which means that anyone may have edited it. It is possible — unlikely, but possible — that someone has added an "example" that is actually malicious code, or inserted malicious code into an existing example. Trust your instincts; if an example seems suspicious to you, if the surrounding text doesn't adequately explain what it does, if it doesn't seem to match the description in the surrounding text, then don't run it. And even if it's clear that an example is non-malicious, it's a good idea to run all of your experiments using an account that has no special privileges or permissions on the system, so you don't (say) accidentally delete something important. Bash is a very powerful systems administration tool, which sometimes means it's a powerful way to accidentally cripple your system! You can crash your smart phone if you're skimming and experimenting on Termux for Android. Rather do your experiments or create labs on an external environment. Virtual machine and sandboxes are good place to do that.

If you are completely new to Bash, or if you have some experience with the Bash command-line but are completely new to programming, you will probably find this book most useful if you begin at the beginning, and work your way through in linear order. If the topic of any section is completely familiar to you, you might want to skim it quickly for possible surprises, rather than skipping it completely; after all, you may not know what you may not know.

If you already have some Bash experience and some programming experience, you can probably skim the entire first half of the book, focusing only on examples that show Bash syntax you aren't already familiar with. That done, you should be in a good position to get the most out of the second half of the book.

If you already have a lot of Bash shell-scripting experience, this may not be the book for you; you will probably learn some things, but not as much as you would learn from the Bash Reference Manual on the Free Software Foundation's web-site, or simply from reading the entirety of man bash. (But this being a wiki, you are invited to share the fruits of your experience!) This book is not a comprehensive reference manual; it focuses on techniques that are either widely used or widely useful, and mostly assumes a typical setup rather than exhaustively documenting all the unusual features that can affect the behavior of a command.