Scenario 3: Monitor Single/Multiple strings in Multiple log files. logsearch.sh localhost /var/tmp/logXray autonda /var/log/messages 60m 'can.*t.*open_P_ntpd.*stat' '.' 1 2 multi_errCheck -ndshow Scenario 2: Monitor MULTIPLE strings in just ONE log file. logsearch.sh localhost /var/tmp/logXray autonda /var/log/messages 60m 'can.*t.*open' '.' 1 2 single_errCheck -ndshow Scenario 1: Monitor ONE string in just ONE log file. Nevertheless, it is done and ready and can be downloaded from the following link: But I recently had to do this and it was quite painful. And yes, it certainly needed to be scripted if you're going to search for multiple strings in multiple different logs at the same time. $ grep -w ‘fatal|error|critical’ /var/log/nginx/error.This was a very time consuming task. To return only those lines where the specified string is a whole word (between non-word characters), use the -w (or –word-regexp) option: So if you were looking for “error”, grep will also print the lines where “error” is embedded in larger words, like “no errors” or “anti-terror”. When searching for a string, grep will display all lines where the string is embedded in larger strings. $ grep -i ‘fatal|error|critical’ /var/log/nginx/error.log To ignore case when searching, call grep with the -i (or –ignore-case) option: This means that uppercase and lowercase characters are treated as different. $ grep ‘fatal|error|critical’ /var/log/nginx/error.logīy default, grep is case sensitive. In the following example, we search for all occurrences of the words fatal, error, and Critical in the Nginx error log file:
String literals are the most basic patterns.
GREP MULTIPLE STRINGS IN A FILE HOW TO
When using extended regular expressions, do not escape the | operator:įor more information on how to build regular expressions, see our Grep regex article. To interpret the pattern as an extended regular expression, call the -E (or –extended-regexp) option to grep. That’s why we’re escaping the OR operator (|) with a forward slash. To keep the special meanings of metacharacters, they must be escaped with a backslash (). When using basic regular expressions, metacharacters are interpreted as literal characters.
The syntax for searching for multiple patterns using the basic grep regular expressions is as follows:Īlways enclose the regular expression in single quotes to prevent shell interpretation and expansion of metacharacters. This operator has the lowest precedence of all regular expression operators. The alternation operator | (pipe) allows you to specify different possible matches which can be literal strings or sets of expressions. To search for multiple patterns, use the OR (alternating) operator. When no regular expression type is specified, grep interprets search patterns as basic regular expressions. GNU grep supports three regular expression syntaxes, basic, extended, and Perl-compatible. Learn how to use grep most efficiently by following the examples in this tutorial. In this guide, we will show you how to use grep to find multiple words or string patterns. This tool prints all the lines that contain the words that you specify as the search pattern.
You can grep multiple strings in different files and directories. Using the grep command, you can customize how the tool looks for patterns or multiple patterns in this case. This name stands for global regular expression printing. Grep is a powerful utility available by default on UNIX-based systems. Check How to Grep for Multiple Strings and Patterns
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