![]() ![]() ![]() You can also run the man command to check the grep command manual page for finding more options. The words that you searched are highlighted in red. You can see the output of this command in the given image. ![]() grep 'warning\|error\|critical' /var/log/syslogīy default search is case sensitive you can make it insensitive by using the option -i we also recommend using option -color to highlight these words. Use option -w with the above command to display only lines that contains these words. Now execute the given command to find these words – grep 'warning\|error\|critical' /var/log/syslog In our example, we will find the warning, error, and critical words in /var/log/syslog which is a log file that stores global system activity data. The strings are the most basic patterns that we use with the grep command. grep -E 'pattern1|pattern2|pattern3' file How to grep multiple strings in a Single Command When using this syntax do not use the escape sequence i.e. You can use option E with the grep command to interpret the pattern as the extended regular expression. grep 'pattern1 \|pattern2\|pattern3' file To search for multiple patterns with the basic regular expression syntax you can use the command as it is given below. egrep 'pattern1|pattern2' *.txtĪnother one is Perl compatible syntax you can try this on older Unix shells. Next is the extended regular expression which is given below. Grep is a command-line option used to find a specific string from inside a file or multiple files or from an output of a command but it can be used only in. The grep command supports three types of the regular expression. The pattern or sequence of character that you want to search using grep in one or more files is known as a regular expression. How to grep multiple Strings on a Linux or Unix system Here are the following examples mention below Example #1 i => it will ignores case for matching Examples of GREP Command in Linux o => Print only the matched parts of a matching line with each such part on a separate output line.Ĭ => it prints only a count of the lines that match a pattern E => Treats pattern as an extended regular expression.For basic usage of this command, you can read the grep command in Linux. Output: It will show a file or directory of the name hello.Įxplanation: in this case, look for a world with file name, hello, and then it will return every line where there’s a match every line where it finds this pattern or this word in this file. So, in this case, it found one line where there was a match and it returned hello world that’s the line. Example #2Įxplanation: We can search multiple files we can do let’s say grip, in this case, our string is just a number eight and we’ll search in two files file1 and file2 so we can just add as many filenames on here as we want and it’ll search for this string inside of each of these files. Example #3Įxplanation: Now if we want to search every file in this current folder let’s see what we have here is five different files if we want to grep “is”. We can search every file in this folder and it returns each line in the word file it found this matches in a zip file it found. Example #4Įxplanation: we can also ignore the case so let’s say we do grep line which will search for the word line in every file in our current folder it only found matches in the word file and it found these three matches those three lines so if we do a grep – it will ignore case so it runs the same search except now it’s going to ignore case so it finds a couple more matches look here we found an all upper case line and here it found a couple of lines where the line is capitalized so the – I is one of the most useful operators to add on to the grep function going to ignore case in your search. ![]()
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