Description<\/strong><\/p>\n\n\n\n grep<\/strong> is a powerful file pattern searcher that comes equipped on every distribution of Linux<\/strong>. <\/p>\n\n\n\n If, for whatever reason, it is not installed on your system, you can easily install it via your package manager (apt-get<\/strong> on Debian<\/strong>\/Ubuntu<\/strong> and yum<\/strong> on RHEL<\/strong>\/CentOS<\/strong>\/Fedora<\/strong>). <\/p>\n\n\n\n Let\u2019s say that you have just installed a fresh copy of the new Ubuntu<\/strong> on your machine, and that you are going to give Python<\/strong> scripting a shot. <\/p>\n\n\n\n You have been scouring the web looking for tutorials, but you see that there are two different versions of Python<\/strong> in use, and you don\u2019t know which one was installed on your system by the Ubuntu<\/strong> installer, or if it installed any modules. <\/p>\n\n\n\n Simply run this command:<\/p>\n\n\n\n First, we ran dpkg \u2013l<\/strong>, which lists installed *.deb<\/strong> packages on your system. <\/p>\n\n\n\n Second, we piped that output to grep \u2013i<\/strong> python, which simple states \u201cgo to grep and filter out and return everything with \u2018python\u2019 in it.\u201d <\/p>\n\n\n\n The \u2013i<\/strong> option is there to ignore-case, as grep<\/strong> is case-sensitive.<\/p>\n\n\n\n Using the \u2013i<\/strong> option is a good habit of getting into, unless of course you are trying to nail down a more specific search.<\/p>\n\n\n\n 2.Search and Filter Files<\/strong> The grep<\/strong> can also be used to search and filter within individual files or multiple files. Lets take this scenario: You are having some trouble with your Apache Web Server<\/strong>, and you have reached out to one of the many awesome forums on the net asking for some help. <\/p>\n\n\n\n The kind soul who replies to you has asked you to post the contents of your \/etc\/apache2\/sites-available\/default-ssl<\/strong> file. <\/p>\n\n\n\n Wouldn\u2019t it be easier for you, the guy helping you, and everyone reading it, if you could remove all of the commented lines? Well you can! Just run this:<\/p>\n\n\n\n The \u2013v<\/strong> option tells grep<\/strong> to invert its output, meaning that instead of printing matching lines, do the opposite and print all of the lines that don\u2019t match the expression, in this case, the #<\/strong> commented lines.<\/p>\n\n\n\n 3. Find all .mp3 Files Only<\/strong> The grep<\/strong> can be very useful for filtering from stdout<\/strong>. <\/p>\n\n\n\n For example, let\u2019s say that you have an entire folder full of music files in a bunch of different formats. <\/p>\n\n\n\n You want to find all of the *.mp3<\/strong> files from the artist JayZ<\/strong>, but you don\u2019t want any of the remixed tracks. Using a find command<\/strong> with a couple of grep<\/strong> pipes will do the trick:<\/p>\n\n\n\n In this example, we are using find to print all of the files with a *.mp3 extension<\/strong>, piping it to grep \u2013i<\/strong> to filter out and prints all files with the name \u201cJayZ<\/strong>\u201d and then another pipe to grep \u2013vi<\/strong> which filters out and does not print all filenames with the string (in any case) \u201cremix<\/strong>\u201d.<\/p>\n\n\n\n 4. Display Number of Lines Before or After Search String<\/strong> Another couple of options are the \u2013A<\/strong> and \u2013B<\/strong> switches, which displays the matched line and number of lines either that come before or after the search string. <\/p>\n\n\n\n While the man page gives a more detailed explanation, I find it easiest to remember the options as \u2013A<\/strong> = after<\/strong>, and \u2013B<\/strong> = before<\/strong>:<\/p>\n\n\n\n The grep\u2019s \u2013C<\/strong> option is similar, but instead of printing the lines that come either before or after the string, it prints the lines in either direction:<\/p>\n\n\n\n Similar to piping a grep<\/strong> string to word count (wc<\/strong> program) grep\u2019s built-in option can perform the same for you:<\/p>\n\n\n\n The \u2013n<\/strong> option for grep<\/strong> is very useful when debugging files during compile errors. <\/p>\n\n\n\n It displays the line number in the file of the given search string:<\/p>\n\n\n\n If you would like to search for a string in the current directory along with all of the subdirectories, you can specify the \u2013r<\/strong> option to search recursively:<\/p>\n\n\n\n Passing the \u2013w<\/strong> option to grep searches for the entire pattern that is in the string. For example, using:<\/p>\n\n\n\n Will print out the line containing the pattern in quotes. On the other hand, if you try:<\/p>\n\n\n\n Nothing will be returned as we are not searching for a pattern, but an entire word.<\/p>\n\n\n\n 10. Search a string in Gzipped Files<\/strong><\/p>\n\n\n\n Deserving some mention are grep\u2019s derivatives. <\/p>\n\n\n\n The first is zgrep<\/strong>, which, similar to zcat<\/strong>, is for use on gzipped<\/strong>files. It takes the same options as grep<\/strong> and is used in the same way:<\/p>\n\n\n\n 11. Match Regular Expression in Files<\/strong> The egrep<\/strong> is another derivative that stands for \u201cExtended Global Regular Expression<\/strong>\u201d. <\/p>\n\n\n\n It recognizes additional expression meta-characters such at + ? |<\/strong> and ()<\/strong>.<\/p>\n\n\n\n egrep is very useful for searching source files, and other pieces of code, should the need arise. <\/p>\n\n\n\n It can be invoked from regular grep by specifying the \u2013E<\/strong> option.<\/p>\n\n\n\n The fgrep<\/strong> searches a file or list of files for a fixed pattern string. <\/p>\n\n\n\n It is the same as grep \u2013F<\/strong>. <\/p>\n\n\n\n A common way of using fgrep<\/strong> is to pass a file of patterns to it:<\/p>\n\n\n\n This is just a starting point with grep<\/strong>, but as you are probably able to see, it is invaluable for a variety of purposes. <\/p>\n\n\n\n Aside from the simple one line commands we have implemented, grep<\/strong> can be used to write powerful cron<\/strong> jobs, and robust shell scripts<\/strong>, for a start.<\/p>\n\n\n\n Description grep is a powerful file pattern searcher that comes equipped on every distribution of Linux. If, for whatever reason, it is not installed on your system, you can easily install it via your package manager (apt-get on Debian\/Ubuntu and yum on RHEL\/CentOS\/Fedora). 1.Search and Find Files Let\u2019s say that you have just installed a fresh copy of the new Ubuntu on your machine, and […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_eb_attr":"","footnotes":""},"categories":[4],"tags":[],"class_list":["post-67","post","type-post","status-publish","format-standard","hentry","category-linux"],"amp_enabled":true,"_links":{"self":[{"href":"https:\/\/bestdedicatedhosting.in\/blog\/wp-json\/wp\/v2\/posts\/67","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/bestdedicatedhosting.in\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/bestdedicatedhosting.in\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/bestdedicatedhosting.in\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/bestdedicatedhosting.in\/blog\/wp-json\/wp\/v2\/comments?post=67"}],"version-history":[{"count":1,"href":"https:\/\/bestdedicatedhosting.in\/blog\/wp-json\/wp\/v2\/posts\/67\/revisions"}],"predecessor-version":[{"id":69,"href":"https:\/\/bestdedicatedhosting.in\/blog\/wp-json\/wp\/v2\/posts\/67\/revisions\/69"}],"wp:attachment":[{"href":"https:\/\/bestdedicatedhosting.in\/blog\/wp-json\/wp\/v2\/media?parent=67"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/bestdedicatedhosting.in\/blog\/wp-json\/wp\/v2\/categories?post=67"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/bestdedicatedhosting.in\/blog\/wp-json\/wp\/v2\/tags?post=67"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}$ sudo yum install grep #RHEL\/CentOS\/Fedora<\/code><\/pre>\n\n\n\n1.Search and Find Files<\/h3>\n\n\n\n
# dpkg -l | grep -i python<\/code><\/pre>\n\n\n\n
<\/p>\n\n\n\n
<\/p>\n\n\n\n# grep \u2013v \u201c#\u201d \/etc\/apache2\/sites-available\/default-ssl<\/code><\/pre>\n\n\n\n
<\/p>\n\n\n\n# find . \u2013name \u201c*.mp3\u201d | grep \u2013i JayZ | grep \u2013vi \u201cremix\u201d<\/code><\/pre>\n\n\n\n
<\/p>\n\n\n\n# ifconfig | grep \u2013A 4 eth0\n# ifconfig | grep -B 2 UP<\/code><\/pre>\n\n\n\n5. Prints Number of Lines Around Match<\/h3>\n\n\n\n
# ifconfig | grep \u2013C 2 lo<\/code><\/pre>\n\n\n\n6. Count Number of Matches<\/h3>\n\n\n\n
# ifconfig | grep \u2013c inet6<\/code><\/pre>\n\n\n\n7. Search Files by Given String<\/h3>\n\n\n\n
# grep \u2013n \u201cmain\u201d setup..py<\/code><\/pre>\n\n\n\n8. Search a string Recursively in all Directories<\/h3>\n\n\n\n
# grep \u2013r \u201cfunction\u201d *<\/code><\/pre>\n\n\n\n9. Searches for the entire pattern<\/h4>\n\n\n\n
# ifconfig | grep \u2013w \u201cRUNNING\u201d<\/code><\/pre>\n\n\n\n# ifconfig | grep \u2013w \u201cRUN\u201d<\/code><\/pre>\n\n\n\n# zgrep \u2013i error \/var\/log\/syslog.2.gz<\/code><\/pre>\n\n\n\n
<\/p>\n\n\n\n# grep \u2013E<\/code><\/pre>\n\n\n\n12. Search a Fixed Pattern String<\/h3>\n\n\n\n
# fgrep \u2013f file_full_of_patterns.txt file_to_search.txt<\/code><\/pre>\n\n\n\n
We hope you\u2019ve found this useful!
<\/p>\n","protected":false},"excerpt":{"rendered":"