So you're looking for: if grep -wq "329," myfile then *), and you don't need -e at all, that would be needed if you wanted to give more than one pattern. You also don't need the -F here, that is only useful if your pattern contains characters with special meanings in regular expressions which you want to find literally (e.g. That will match if you find your target string as a standalone "word", as a string surrounded by "non-word" characters. This option has no effect if -x is also specified. Word-constituent characters are letters, digits, and the Of the line or followed by a non-word constituent character. The test is that the matching substring must either beĪt the beginning of the line, or preceded by a non-wordĬonstituent character. Select only those lines containing matches that form whole The option you want is -w: -w, -word-regexp So it is only useful if you want to find lines that contain nothing other than the exact string you are looking for. The pattern and then surrounding it with ^ and $. Select only those matches that exactly match the whole line.įor a regular expression pattern, this is like parenthesizing That means (from man grep): -x, -line-regexp This is because /l*/ means ‘ match letter l zero or more times‘, so /l*c/ means ‘ match letter c preceded by zero or more occurrences of letter l‘, but any line that contains the letter c in it also contain zero or more letters l in front of it - the key to understanding this is “ ZERO or more times“.ĬONCLUSION: In REGEXP the asterisk symbol (*) does not mean the same thing as in Microsoft Windows and DOS/CMD file-name matching, it does not match any character (as this tutorial erroneously suggests), it matches the preceding character ZERO or more times.The -x isn't relevant here. The above will match all lines that contain the letter ‘c’ regardless whether they contain the letter ‘l’ or not. The example below prints all the lines in the file /etc/hosts since no pattern is given. In the following examples, we shall focus on the meta characters that we discussed above under the features of awk. The 'script' is in the form '/pattern/ action' where pattern is a regular expression and the action is what awk will do when it finds the given pattern in a line. This is repeated on all the lines in the file. It works by reading a given line in the file, makes a copy of the line and then executes the script on the line. Where 'script' is a set of commands that are understood by awk and are execute on file, filename. The general syntax of awk is: # awk 'script' filename But for the scope of this guide to using awk, we shall cover it as a simple command line filtering tool. You can think of awk as a programming language of its own. In order to filter text, one has to use a text filtering tool such as awk.
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