7/5/2023 0 Comments Unix grep usage![]() This will print a wall of console output to the terminal, something that we can search using grep. * as previously mentioned - the dot is a wildcard character, and the star, when modifying the dot, means find one or more dot ie. Open a terminal and run the dmesg command as sudo. If you want * in regular expressions to act as a wildcard, you need to use. ![]() However, in regular expressions, * is a modifier, meaning that it only applies to the character or group preceding it. In the console, * is part of a glob construct, and just acts as a wildcard (for instance ls *.log will list all files that end in. Whether the patterns come from the command line or from a file doesnt matter. Example: grep -e pattern1 -e pattern2 filename In extended regular expressions ( grep -E ), you can use to combine multiple patterns with the OR operation. Using multiple -e options matches anything that matches any of the patterns, giving the OR operation. * in a regular expression is not exactly the same as * in the console. With no argument, grep expects basic regular expressions with -E, grep expects extended regular expressions with -P (if supported), grep expects Perl regular expressions and with -F, grep expects literal strings. 6 Answers Sorted by: 62 There are lot of ways to use grep with logical operators. * - grep 'abc.*def' myFile will match a string that contains abc followed by def with something optionally in between. The Options The main options we will use in this tutorial are -P, -v, -i, -c, -color, -L, and -l. Grep will by default display any lines in a file that contain the expression. The basic usage of the command is grep options expression filename. For your more complex match, you need to use. Grep stands for Globally search a Regular Expression and Print. If you want to just match abc, you could just say grep 'abc' myFile. ![]() * - the dot means any character ( within certain guidelines). If you want to match anything, you need to say. sh script that just echos all the arguments. One way to try out how Bash passes arguments to a script/program is to create a. *abc*/ matches a string containing ab and zero or more c's (because the second * is on the c the first is meaningless because there's nothing for it to repeat). So you really need to escape it twice (if you prefer not to use the other mentioned answers). The asterisk is just a repetition operator, but you need to tell it what you repeat. ![]()
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