Introducing findstr

Chapter 13

Figure 13-1

You cannot use the following command on its own from the command line, or you will receive a bad command error, as shown in Figure 13-2:

findstr

Figure 13-2

It is essential that you use one or more of the command-line switches and parameters that specify what findstr is to do.

Finding Literal Text

One of the simplest tasks that findstr can be used for is to match literal text. The general form of a findstr command to perform simple literal matching in a single file is as follows:

findstr “Text of interest” Filename.suffix

Strictly speaking, you supply a regular expression pattern that consists only of literal characters to be matched.

The test file, Hello.txt, is shown here:

Hello world!

Hello with initial upper-case.

hello with initial lower case.

Goodbye!

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Regular Expressions Using findstr

Notice that two lines have Hello with an initial uppercase H, and one line has hello with an initial lowercase h.

1.Open a command window, and navigate to the directory into which you downloaded the test file Hello.txt.

2.Type the following command at the command line:

findstr “Hello” Hello.txt

3.Press Return, and inspect the results returned by findstr. Figure 13-3 shows the result. The two lines containing Hello (initial uppercase H) are displayed, while the line containing hello (initial lowercase h) is not. This is because the default behavior of findstr is to match case sensitively.

Notice that the content of two lines is displayed, but no indication of the file they come from or the line number is given. When you use findstr to examine multiple files, that additional information is useful.

Figure 13-3

4.The sample file, Hello.txt, has everything neatly on separate lines, but not all documents are so simply structured. Therefore, it is often useful to have line numbers displayed along with the text on a particular line, because that allows you to scan to roughly the right point in a long document to see what the context is. To display line numbers from findstr, use the /n switch.

Type the following command on the command line, and press Return:

findstr /n “Hello” Hello.txt

5.Inspect the results returned when the /n switch was added to the command. Figure 13-4 shows the result. Notice that the line number is now displayed for each line of the test file that contains matching text.

Particularly when the command line has been repeated using F3 and then edited, the findstr utility can sometimes fail to find any matches even though matches exist. If you find an unexpected failure to match any results, I suggest that you type the desired command afresh. This, in my experience, fixes the problem.

Chapter 13

6.If you wish matching to be carried out case insensitively, you can use the /i switch. Type the following command at the command line, and press Return:

findstr /i /n “Hello” Hello.txt

Figure 13-5 shows the results. Notice that all three lines containing Hello or hello are now displayed.

Figure 13-5

There are some findstr command-line switches that substitute functionally for regular expressions’ metacharacters. They will be discussed in the relevant place when the supported metacharacters are covered in the next section.

Metacharacters Suppor ted by findstr

The findstr utility supports many regular expression patterns, but perhaps because it is used on the command line, the utility has many nonstandard pieces of regular expression syntax (refer to the following table).

As noted in the preceding table, some metacharacters are not supported. The following table lists findstr command-line switches that perform functions similar to regular expression metacharacters in many other

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Regular Expressions Using findstr

settings, as well as command-line switches with other meanings. Command-line switches that take arguments are described in a separate table.

The following command-line switches each take an argument that affects their behavior:

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