{"id":83,"date":"2013-01-02T10:22:36","date_gmt":"2013-01-02T10:22:36","guid":{"rendered":"http:\/\/www.linuxcloudvps.com\/blog\/?p=83"},"modified":"2023-08-29T11:46:32","modified_gmt":"2023-08-29T16:46:32","slug":"83","status":"publish","type":"post","link":"https:\/\/www.linuxcloudvps.com\/blog\/83\/","title":{"rendered":"Grep command examples"},"content":{"rendered":"\n<p>Grep is one of the most used commands in Unix (or Linux). The name &#8220;grep&#8221; means &#8220;general regular expression parser&#8221; The grep command is used to search for text strings or regular expressions within one or more files. It can be very useful in your daily administration work on your <a title=\"Cloud Hosting\" href=\"https:\/\/www.linuxcloudvps.com\/\" target=\"_blank\" rel=\"noopener\">Linux Cloud Hosting<\/a> account.<\/p>\n\n\n\n<!--more-->\n\n\n\n<p>The basic syntax of grep is:<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">grep pattern target_file<\/pre>\n\n\n\n<p>OK, now that we have the theory, let&#8217;s see some practical examples.<\/p>\n\n\n\n<p>1. Searching for a text string in one file<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">grep 'root' \/etc\/passwd<\/pre>\n\n\n\n<p>2. Searching for a string in multiple files<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">grep 'root' \/etc\/*<\/pre>\n\n\n\n<p>The wild card matches all files in the \/etc\/directory<\/p>\n\n\n\n<p>3. Showing matching line numbers (-n)<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">grep -n 'root' \/etc\/passwd<\/pre>\n\n\n\n<p>4. Counting the number of matches (-c)<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">grep -c 'root' \/etc\/passwd<\/pre>\n\n\n\n<p>5. Recursive search (-r or -R)<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">grep -r \"string\" \/home\/<\/pre>\n\n\n\n<p>Search for the string &#8216;string&#8217; in all the files in the home directory and all its subdirectories.<\/p>\n\n\n\n<p>6. Invert match (-v)<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">grep -v 'root' \/etc\/passwd<\/pre>\n\n\n\n<p>Displays the lines which does not matches the given string<\/p>\n\n\n\n<p>7. Display only the file names which matches the given pattern (-l)<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">grep -rl \"string\" \/home\/<\/pre>\n\n\n\n<p>8. Search for full words not partial matches within words (-w)<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">grep -w \"fullstring\" \/home\/<\/pre>\n\n\n\n<p>9. Show only the matched string, not the whole line (-o)<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">grep -o \"fstring\" \/home\/<\/pre>\n\n\n\n<p>10. Advanced usage of grep<\/p>\n\n\n\n<p>&#8211; find out process pid<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">ps aux | grep someprocess<\/pre>\n\n\n\n<p>&#8211; multi patterns<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">grep -iE \"(something|somethingelse)\" file<\/pre>\n\n\n\n<p>&#8211; determine which services are enabled at boot<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">chkconfig --list | grep $(runlevel | awk '{ print $2}'):on<\/pre>\n\n\n\n<p>&#8211; search for IP addresses<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">grep -Eo '([0-9]{1,3}\\.){3}[0-9]{1,3}' \/var\/log\/maillog<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Grep is one of the most used commands in Unix (or Linux). The name &#8220;grep&#8221; means &#8220;general regular expression parser&#8221; The grep command is used to search for text strings or regular expressions within one or more files. It can be very useful in your daily administration work on your Linux Cloud Hosting account.<\/p>\n","protected":false},"author":2,"featured_media":84,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[12],"tags":[30,28,27,132,29],"class_list":["post-83","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-tips-and-tricks","tag-command","tag-grep","tag-linux","tag-linuxcloudvps","tag-parsing"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.2 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Grep command examples | LinuxCloudVPS Blog<\/title>\n<meta name=\"description\" content=\"Grep is one of the most used commands in Unix (or Linux). 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