How to use the Linux read command and read file contents

[How to use the Linux read command to read the contents of a file]

In the Linux system, read is a command used to read data from standard input or files. . Using the read command can help users quickly obtain the file content and perform subsequent processing. The following will introduce in detail how to use the Linux read command to read the file contents, including specific code examples.

1. Read the file content

To read the file content, you first need to open the terminal and use the following command format to read the file content:

read [-options] [variable]

Among them, -options represents various options, variable represents the variable name, used to store the read data.

2. Code Example

Suppose we have a text file named example.txt with the following content:

Hello, this is an example file.
Welcome to the world of Linux.

Now We will use the read command to read the contents of this file and store it in a variable. Enter the following command in the terminal:

while IFS= read -r line; do
    echo "$line"
done < example.txt

After executing the above command, the terminal will output the contents of the file example.txt:

Hello, this is an example file.
Welcome to the world of Linux.

In the above code example, while loop is used to read the file content line by line, IFS= is used to prevent the read command from removing spaces in the line, -r option is used to retain the backslash character original form.

3. Read specified lines

Sometimes we just want to read specific lines in the file, you can use the following command:

read -r line_num < example.txt
sed -n "${line_num}p" example.txt

The above code will First read the contents of the specified line in the file, and then use the sed command to output the contents of the line.

4. Other options

In addition to the methods mentioned in the example, the read command also has some other commonly used options, such as -t for Set the timeout, -s is used for confidential input, -n is used to limit the number of characters read, etc.

5. Conclusion

Through the above method, we can flexibly use the Linux read command to read the file content, which is very useful when performing tasks such as text processing and data analysis. I hope this article can help you better understand and apply the read command.

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