This would have taken some considerable time in Perl, Python, or Ruby even when using a nicely implemented DNS Library.While powerful, redirection can get complicated for newer CentOS Administrators. To obtain a list of possible matches, press Esc = after entering the first few characters.It is important to note that > redirection operator creates a new file, or truncates an existing file when used. For example attempting to find the location of the history command (which is actually built into the shell rather than existing as an executable on the file system) will result in output similar to the following:Once the execute bit has been set on the file’s permissions, it may be executed directly. For example, to redirect the contents of a file as input to a command:Many shell commands take one or more filenames as arguments. interactive command interpreter environment within which commands may be typed at a prompt or entered into a file in the form of a script and executed For example, to assign the current date and time to an environment variable called NOW:Yet another early creation was the C shell which shared some syntax similarities with the C Programming Language and introduced usability enhancements such as command-line editing and history.Unfortunately a detailed overview of shell scripting is beyond the scope of this chapter. Arguably one of the most powerful aspects of the shell involves the ability to create shell scripts. Output against google.com domain −Let's see how this works −Processing stdout to another command −BASH can be a little tricky compared to a dedicated scripting language. Fortunately Bash provides a wide range of command line editing options as outlined in the following table:Both stderr and stdout may be redirected to the same file using the &> operator:You can create your own environment variables using the export command. Once familiar with the concepts you will quickly find that it is quicker to perform many tasks using the shell in a terminal window than it is to wade through menus and dialogs on the desktop.Output from a command can be redirected from stdout to a physical file on the file system using the ‘>’ character. This could be further restricted to any file names beginning with list and ending in .txt:So far we have focused exclusively on the interactive nature of the Bash shell.
By interactive we mean manually entering commands at the prompt one by one and executing them. The first widely used shell was the Bourne shell, written by Stephen Bourne at Bell Labs.The above command will display the number of lines contained in files.txt file.The above command will display the content of all files ending with a .txt extension.