3 - Weber State University

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106 Chapter 3 Exploring Linux Filesystems you typically use the program that was used to create the file. However, some commands can be used to safely display the contents of most binary files. The strings command searches for text characters in a binary file and outputs them to the screen. In many cases, these text characters might indicate what the binary file is used for. For example, to find the text characters inside the /bin/echo binary executable program page-by-page, you could use the following command: [root@server1 ~]# strings /bin/echo | more /lib/ld-linux.so.2 PTRh|
© Cengage Learning. All rights reserved. No distribution allowed without express authorization. Searching for Text Within Files Recall that Linux was modeled after the UNIX operating system. The UNIX operating system is often referred to as the “grandfather” of all operating systems because it is over 40 years old and has formed the basis for most advances in computing technology. The major use of the UNIX operating system in the past 40 years involved simplifying business and scientific management through database applications. As a result, many commands (referred to as text tools) were developed for the UNIX operating system that could search for and manipulate text, such as database information, in many different and advantageous ways. A set of text wildcards was also developed to ease the searching of specific text information. These text wildcards are called regular expressions (regexp) and are recognized by several text tools and programming languages, including, but not limited to, the following: ● grep ● awk ● sed ● vi ● Emacs ● ex ● ed ● C++ ● PERL Searching for Text Within Files 107 ● Tcl Because Linux is a close relative of the UNIX operating system, these text tools and regular expressions are available to Linux as well. By combining text tools (as you will see later), a typical Linux system can search for and manipulate data in almost every way possible. As a result, regular expressions and the text tools that use them are commonly used in business today. Regular Expressions As mentioned earlier, regular expressions allow you to specify a certain pattern of text within a text document. They work similarly to wildcard metacharacters in that they are used to match characters, yet there are many differences: ● Wildcard metacharacters are interpreted by the shell, whereas regular expressions are interpreted by a text tool program. ● Wildcard metacharacters match characters in filenames (or directory names) on a Linux filesystem, whereas regular expressions match characters within text files on a Linux filesystem. ● Wildcard metacharacters typically have different definitions than regular expression metacharacters. ● More regular expression metacharacters are available than wildcard metacharacters. 3
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3 - Weber State University

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