![]() The backslash retains its special meaning only when followed by one of the following characters: $, `, ", \, or newline. If you double quote your regex, the shell treats backslashes specially (emphasis mine): I suspect grep itself does something special with the literal string \\|. So all double-quotes are removed and the backslashes and pipes are not altered by the shell. I investigated what my shell does with the command lines above : Using this simple argument-printing program, void main(int argc, char** argv) Escaping with three backslashes fails, echo abcdef | grep -e"def\\\|zzz"ĭoes anyone have an explanation, especially for the 2-backslash case ? More surprisingly, escaping with 2 backslashes also works, echo abcdef | grep -e"def\\|zzz" Escaping with one backslash works, echo abcdef | grep -e"def\|zzz" Outputs nothing, because grep is not in extended regex mode. We hope that this article has helped you to better understand Grep Regex and its usage.I'm a little confused about how many backslashes are needed to escape the alternation operator | in regular expressions for grep. In this article, we provided a comprehensive guide to Grep Regex, including a detailed description, usage with code examples, and related concepts. It is used to search for patterns in files using regular expressions. Grep Regex is a powerful tool that is widely used in Linux and Unix systems. Sed supports regular expressions and can be used to perform various operations on text, such as search and replace. It is often used in conjunction with Grep. Sed is another command-line utility that is used to manipulate text. Grep supports various options and regular expressions. It is a powerful tool that is widely used in Linux and Unix systems. Grep is a command-line utility that is used to search for patterns in files. Regular Expressions are used in various programming languages and tools, including Grep. They are used to match and manipulate text. Regular Expressions are a sequence of characters that define a search pattern. In this section, we will discuss some related concepts that can help you to better understand Grep Regex. -c – Displays the count of the number of lines that match the pattern.įor example, to search for the word “hello” in a case-insensitive manner and display the line number of each matching line, you would use the following command: grep -in hello file.txt Related Concepts.-n – Displays the line number of each matching line.-v – Inverts the search, i.e., displays all lines that do not match the pattern.Grep also supports various options that can be used to customize the search. The backslash ( ) is used to escape the | symbol. Here, the | symbol is used to specify the “or” condition. () – Groups a set of regular expressions.įor example, to search for any line that contains the word “hello” or “world”, you would use the following command: grep 'hello|world' file.txt.– Matches any character that is not enclosed in the square brackets. ![]()
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