How to Efficiently Delete a Specific Line from a File in PHP?

Deleting Lines from a File Using PHP

Removing specific lines from a text file can be a common task in PHP development. Suppose you have a file named $dir and a $line variable representing a complete line in the file. However, you don't know its line number. To delete this line, you can use the following steps:

1. Read the Contents of the File:

$contents = file_get_contents($dir);

2. Perform String Manipulation to Remove the Line:

str_replace can substitute occurrences of $line with an empty string:

$contents = str_replace($line, '', $contents);

3. Update the File with the Modified Contents:

file_put_contents($dir, $contents);

This code replaces the $line with an empty string, effectively erasing the line from the file. Note that file_put_contents will overwrite the existing file contents, so make sure you have any necessary backups in place.

awk Method:

While the above method is simple and straightforward, you can also use awk to delete the line:

awk -F'\r' '!/^$line$/' $dir > /tmp/file.txt

• -F'r': Specifies line termination as carriage return (r).
• !/^$line$/: Inverts grep logic to print all lines except the specified one.
• /tmp/file.txt: Write the output to a temporary file.

Once you have the updated file, you can replace the original with the temporary one:

mv /tmp/file.txt $dir

This method is particularly useful when dealing with large files where line numbers are unknown.

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