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110 Chapter 3 Exploring Linux Filesystems Keep in mind that the text being searched is case sensitive; to perform a search that is not case sensitive, use the –i option to the grep command: [root@server1 ~]# grep "algonquin park" project4 [root@server1 ~]#_ [root@server1 ~]# grep –i "algonquin park" project4 room this year while vacationing in Algonquin Park - I I have been reading on the history of Algonquin Park but [root@server1 ~]#_ Another important note to keep in mind regarding text tools such as grep is that they match only patterns of text; they are unable to discern words or phrases unless they are specified. For example, if you want to search for the lines that contain the word “we,” you can use the following grep command: [root@server1 ~]# grep "we" project4 Hi there, I hope this day finds you well. Unfortunately we were not able to make it to your dining [root@server1 ~]#_ However, notice from the preceding output that the first line displayed does not contain the word “we”; the word “well” contains the text pattern “we” and is displayed as a result. To display only lines that contain the word “we,” you can type the following to match the letters “we” surrounded by space characters: [root@server1 ~]# grep " we " project4 Unfortunately we were not able to make it to your dining [root@server1 ~]#_ All of the previous grep examples did not use regular expression metacharacters to search for text in the project4 file. Some examples of using regular expressions (see Table 3-4) when searching this file are shown throughout the remainder of this section. To view lines that contain the word “toe” or “the” or “tie,” you can enter the following command: [root@server1 ~]# grep " t.e " project4 especially wished to see the model of the Highland Inn and the train station in the dining room. I have been reading on the history of Algonquin Park but no where could I find a description of where the Highland [root@server1 ~]#_ To view lines that start with the word “I,” you can enter the following command: [root@server1 ~]# grep "^I " project4 I have been reading on the history of Algonquin Park but I need not wait until next year when I visit your lodge? [root@server1 ~]#_ © Cengage Learning. All rights reserved. No distribution allowed without express authorization.
© Cengage Learning. All rights reserved. No distribution allowed without express authorization. To view lines that contain the text “lodge” or “lake,” you need to use an extended regular expression and the egrep command, as follows: [root@server1 ~]# egrep "(lodge|lake)" project4 Inn was originally located on Cache lake. I need not wait until next year when I visit your lodge? [root@server1 ~]#_ Editing Text Files Recall that text files are the most common type of file modified by Linux users and administrators. Most system configuration is stored in text files, as is commonly accessed information such as e-mail and program source code. Consequently, most Linux distributions come with an assortment of text editors, and many more are available for Linux systems via the Internet. Text editors come in two varieties: editors that can be used on the command line, including vi (vim), nano, and Emacs, and editors that must be used in a GUI environment, including Emacs-x and gedit. The vi Editor The vi editor (pronounced “vee eye”) is one of the oldest and most popular visual text editors available for UNIX operating systems. Its Linux equivalent (known as vim, which is short for “vi improved”) is, therefore, standard on almost every Linux distribution. Although the vi editor is not the easiest of the editors to use when editing text files, it has the advantage of portability. A Fedora Linux user who is proficient in using the vi editor will find editing files on all other UNIX and Linux systems easy because the interface and features of the vi editor are nearly identical across Linux and UNIX systems. In addition, the vi editor supports regular expressions and can perform over 1,000 different functions for the user. To open an existing text file for editing, you can type vi filename (or vim filename) where filename specifies the file to be edited. To open a new file for editing, simply type vi or vim at the command line: [root@server1 ~]# vi The vi editor then runs interactively and replaces the command-line interface with the following output: ~ ~ ~ ~ ~ ~ VIM - Vi IMproved ~ ~ version 7.2.411 ~ by Bram Moolenaar et al. ~ Modified by ~ Vim is open source and freely distributable Editing Text Files 111 3
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