The chmod command can be used with the -R or -recursive options in order to change files and folders permission recursively. Change Files and Folders Permissions Recursively with chmod chmod recursive is a popular operation where given access permissions are set for the specified folder and all of its contents and sub-folders and files. By using the permission unwanted users can not access, read, or change given files and folders. This regulation is called files and folder permissions where every file and folder can be set for different permission for different operations. e is strictly the flag for indicating the pattern you want to match against.Linux uses file permission in order to regulate access, modification of the files, and folders. E (extended-regexp) controls whether you need to escape certain special characters. We can search multiple patterns or strings using OR operator | and \|. Operator:x:11:0:operator:/root:/sbin/nologin Search multiple strings Uucp:x:10:14:uucp:/var/spool/uucp:/sbin/nologin We can use -B option to display N lines before the string for a given file $ grep -B 2 "root" /etc/passwd Gopher:x:13:30:gopher:/var/gopher:/sbin/nologin Display lines before the string match Operator:x:11:0:operator:/root:/sbin/nologin The -A option which displays the N lines after the string match. This may be obtained from: Display lines after the string match # For a step to step guide on installing, configuring and using samba, Samba has a huge number of configurable options (perhaps too
# This is the main Samba configuration file. The -w (word-regexp) flag for grep will make the given expression match only whole words.
I : This option ask grep command to ignore the case while matching the pattern. This option instructs grep command to print only the matching words instead of entire line. O : By default, grep prints entire line which contains the search pattern. The following command will extract all links from an file $ grep –Eoi ']+>.*' filename
Use -E ( or -extended-regexp) option if you want grep to understand it as an extended regular expression. In the following example, the string ^welcome will match only if it occurs at the very beginning of a line. The ^ (caret) symbol - The pattern following it must occur at the beginning of each line. Basic and Extended are the two regular expression used by grep command.īy default, grep interprets the pattern as a basic regular expression. Regular Expressions is a pattern to match for each input line. $ ps -ef | grep docker | grep apache Regular Expressions in files Here i am doing multiple pipe and searching for the 'docker' and 'apache' process from ps command. In the following example I am searching for a file with name 'backup' using the ls command $ ls | grep backup You can use pipe the output for a command and grep for the pattern from its output. $ grep -r nginx /var Search for a String in Command Output (stdout) In the following example, grep command will search for the string 'ngnix' in all files inside /var directory. Recursive search is achieved by using -r option that will search Recursively all file skipping symbolic links. Haldaemon:x:68:68:HAL daemon:/:/sbin/nologin Recursive Search In following examples grep matches all the words such as “hal”, “HAL” case insensitively: $ grep -i HAL /etc/passwd Options -i searches for the given string/pattern case insensitively. etc/group:wheel:x:10:root Grep case insensitive search etc/passwd:operator:x:11:0:operator:/root:/sbin/nologin
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