How to efficiently delete the content at the end of a file in Linux

Linux is an open source operating system widely used in server environments and development work. In the daily use of Linux, we often encounter situations where we need to delete the content at the end of a file, such as clearing log files, removing redundant data, etc. This article will introduce how to efficiently delete the content at the end of a file in Linux and provide specific code examples.

In Linux, we can use some commands and techniques to delete the content at the end of the file. Two common methods will be introduced below.

Method 1: Use the truncate command

truncate command can be used to truncate the file, and can be passed --size Parameter to specify the truncation size. We can use this feature to delete the content at the end of the file. The specific operations are as follows:

1. First, use the cat command to view the contents of the original file:

cat file.txt

2. Then, use wc Command to get the total number of lines in the file:

total_lines=$(wc -l < file.txt)

3. Next, calculate the number of lines that need to be retained. For example, we want to delete the 100 lines at the end of the file:

keep_lines=$((total_lines - 100))

4. Finally, use the truncate command to perform the file truncation operation:

truncate -s $((keep_lines * 1)) file.txt

Through the above steps, we have successfully deleted the specified number of lines at the end of the file.

Method 2: Use the sed command

sed is a flow text editor that can perform various operations on text, including Delete rows etc. We can use the sed command to delete the content at the end of the file. The specific operations are as follows:

1. First, use the cat command to view the contents of the original file:

cat file.txt

2. Then, use wc Command to get the total number of lines in the file:

total_lines=$(wc -l < file.txt)

3. Next, calculate the number of lines that need to be retained. For example, we want to delete the 100 lines at the end of the file:

keep_lines=$((total_lines - 100))

4. Finally, use the sed command to delete the content at the end of the file:

sed -i "${keep_lines},$ d" file.txt

Through the above steps, we also successfully deleted the content of the specified number of lines at the end of the file. .

To sum up, this article introduces how to efficiently delete the tail content of files in Linux and provides specific code examples. Readers can choose the appropriate method to delete the content at the end of the file according to actual needs. Hope this article is helpful to everyone.

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