There are options to better format results, list files and line numbers containing matches, provide context for results by printing the lines surrounding a match, and much more. The grep command has far more options than I demonstrated in this article. These numbers are returned because they include 1, which is among the list of digits to match.Īs you can see, regex is something of a puzzle, but through experimentation and practice, you can get comfortable with it and use it to improve the way you grep through your data. So instead, you can use + to match a single character at least once and then again as many times as necessary until the end of the word:Īre you surprised to see 11 in a search for digits 1 to 9? There are definitely no three-letter country names in this list. Because you know the list you're dealing with, you know that zero times is useless in this instance. Using the * character, you can tell grep to match a single character zero or as many times as necessary until it reaches the end of the word. character can only ever match a single character unless you level it up. The important thing is to analyze the results, so you understand why.Īdvanced regex requires the -extended-regexp or -E option.įor instance, this fails to return any country: $ grep -E A.a example.txt matches the preceding item four (or any number you enter in the braces) timesĪrmed with this knowledge, you can practice regex on example.txt all afternoon, seeing what interesting combinations you come up with.+ matches the preceding item one or more times.
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