1/21/2024 0 Comments Grep pattern with spaceThis is one of the most useful examples, in my opinion, as I often find myself in a situation where I have to look for a string followed by the other. Here, I've used the -n flag which will print the number of the line from where the keyword was found. So lets I want to look for "apple" or "pear" or "mango" from the fruits.txt, then, I will be using the following command: grep -E -n"apple|mango|pear" fruits.txt Similarly, you can use the -E flag to avoid using \ to separate different patterns: grep -E "String1|String2|String3" File.txt In the above snapshot, in the left window, I have used the cat command to print the file contents and in the right window, I have used the command that gave me the output with the specific requirement. ![]() So let's say you have to look for one or the other (either this or that situation) and in that case, you can use the grep command in the following manner: grep "String1\|String2" File.txtįor example, here, I want to look for the lines containing apple or orange in the fruits.txt file, then I will be using the following: grep "apple\|orange" fruits.txt Now, let's have a look at some practical examples. NOT ( -v): It is used when you want everything but not the output from the given pattern.OR ( | in regular expressions): It is used when you want to get results from at least one of the multiple patterns and will give you output if any of the given patterns match. ![]() * in regular expressions): It is used to search multiple patterns in a specific order and it will ensure that the given multiple patterns are in the same line. When you consider using multiple patterns with grep, you are given three operators: AND, OR, and NOT and each has a different meaning. How to use multiple patterns with the grep command Well, it is pretty easy to use multiple patterns, and in this tutorial, I will share several examples of how you can use various patterns with the grep command. And there's nothing wrong with it.īut how would you use the grep command when you have to specify multiple patterns to get the desired output? Turn takes precedence over alternation.Most Linux users use the grep command daily to sort specific keywords in a file. Repetition takes precedence over concatenation, which in Two regular expressions can be joined by the infix operator | the resulting regular expression matches any string Nating two substrings that respectively match the concatenated subexpressions. Regular expression matches any string formed by concate. Two regular expressions can be concatenated the resulting : ? ^ _ ` The preceding item is matched at least n times, but not more than m times. Any char from the `' class, and any char not in the '' class. octal codes 000 through 037, or 'DEL' (octal 177) A range of characters can be specified by giving the first and last charac. List is the caret ^ then it matches any character not in Meaning can be quoted by preceding it with a backslash.Ī list of characters enclosed by matches any single character in that list if the first character of the Including all letters and digits, are regular expressions The fundamental building blocks are the regular expressions that match a single character. The following descriptionĪpplies to extended regular expressions differences forīasic regular expressions are summarized afterwards. In other implementations, basic regular expres. Is no difference in available functionality using either ![]() Grep understands two different versions of regular expression syntax: "basic" and "extended." In GNU grep, there To arithmetic expressions, by using various operators to Regular expressions are constructed analogously Regular ExpressionsĪ regular expression is a pattern that describes a set of Egrep is the same as grep -E.įgrep is the same as grep -F. Variant programs egrep and fgrep are available. By default, grep prints the matching lines. Grep searches the named input FILEs (or standard input if no filesĪre named, or the file name - is given) for lines containing a match to the Search input files for lines that match a given pattern.
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