That egrep command searches for those three strings (regular expressions, really) in all files in the current directory. An easier egrep commandīefore I go away, here's an easier egrep command to look at: Also, specify the name of the file that contains the text. While my original locate -i calendar command shows nearly 3,000 files, the locate command combined with grep and egrep in this manner shows only 15 files. Find Text in Files To search for text pattern in a file, simply run grep followed by the pattern name. I used the -v argument to perform the "opposite" meaning of a normal egrep command, so strings with these patterns were not shown and also used the -i argument to perform a case insensitive egrep search here. Used the egrep command with multiple regex patterns to reduce the output much more.Used the grep command so the output would only display files and directories with the string "Users" in them.Used to locate command with the case-insensitive option to find all files with the string "calendar" in them. Locate -i calendar | grep Users | egrep -vi 'twiki|gif|shtml|drupal-7|java|PNG'Īs you can see from that command, I did this: In figure 5.1, the grep command is used to capture the line containing the authors of a text, which is then redirected it to a text file.Summary: How to use the Linux egrep command with multiple regular expressions (regex patterns).Īs a quick note here today, I just used the Linux egrep command to perform a case-insensitive search on multiple regular expressions (regex patterns). Really, what I did was a little more complicated: The grep command uses regular expressions as search patterns to capture patterns in files and outputs it to stdout. So for sed, tr and sort you have to use \.ĭatafile 1: Pseudomonas Aeruginosa 16S rRNA Genebank file However, only grep has the -E command line argument and an extended version. The second and third solution similar, as they both use extended grep, so that BASH interprets the commands as extended regex. In the first solution, we use '\' to designate that '|' is to be interpreted as a special character. There would be no results, as BASH doesn't interpret '|' as a special character. You will get an output like below: root:x:0:0:root:/root:/bin/bash vega:x:1000:1000:vega:/home/vega:/bin/bash. For example, if you wanted to search for instances of 'AUTHORS' or 'authors' Translates characters from the standard input and writes to the standard output.īefore you start using these commands you should know that BASH (recall that this is shell that you're working in) uses basic regex and not extended regex by default. Option examples -E grep -E ja(scks)on filename, Extended regex (lines containing jason or jackson) -c, grep -c error /var/log/syslog, Count the number. Uses regular expressions to search for patterns in a file.Īllows user to edit files without actually opening the files using regular expressions. Now that you've been initiated in regular expressions, we'll take a look at some Unix commands that use regular expressions
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