What is the function of the grep -e command on Linux?

The purpose of the grep -e command in Linux is to specify one or more matching patterns to search for in files or standard input, and output the matching results.

The syntax of the command is as follows:
grep -e pattern file

The pattern is a regular expression used to specify the pattern to search for, which can be a simple string or a complex regular expression. The file is the name of the file to search in; if no file name is specified, it will default to searching data from standard input.

The grep -e command searches through each line in a file or standard input, and if a line matches the specified pattern, it will output that line to the standard output.常用的选项包括 can include:

-i: Match ignoring case.
-v: Reverse match, only output lines that do not match.
-r: Recursive search in folders.
-l: Only output matching file names.
-n: Output line numbers of matching lines.

For example, to search for lines containing the string “hello” in the file file.txt, you can use the following command:
grep -e “hello” file.txt