IT Systems, Networks, Security and Education
This is post 11 of 11 in the series “The Linux Command Line” The first principle of file creation is that when you, as a specific user, create a file, it will be owned by you, and your default group will have some default permissions set on that file. Remember the User – Group – …
Continue reading “Linux: Creating and Deleting Directories and Files”
This is post 10 of 11 in the series “The Linux Command Line” The ls Command ls = List of objects in the current working directory. Typing: ls will bring up a list of files and subdirectories. It may also be flagged to provide some different ways of looking at the list of files, such …
Continue reading “Listing Files and Going Deep Into Filesystems”
This is post 5 of 11 in the series “The Linux Command Line” When you start a shell session, it opens in your home directory. This is true in all OSs, and even the paths are similar. In Windows: C:\Users\username\ In Mac: /Users/username/ In Linux: /home/username/ or /users/username/ Why home? It keeps your stuff segregated …
This is post 3 of 11 in the series “The Linux Command Line” Boot, login, and start Secure Telnet/Secure Shell or PuTTY. Log in with your UNM user name and password. Check Your Shell Command: echo $SHELL Your answer may be: /bin/sh # the Bourne shell /bin/csh # the C shell /bin/bash # the Bourne …
This is post 2 of 11 in the series “The Linux Command Line” Let’s be clear: the structure of directories in any OS is a directory tree. You, I and everyone will want to call it a “file system.” That’s okay, and the other kids usually won’t laugh at you. But formally, a file system …
This is post 13 of 19 in the series “[ Shell Scripting ]” Arguments For our first trick, we’re going to write a script that shows us how arguments are dealt with by scripts. Start a new script called args. (Notice that it doesn’t have to be “args.sh”.) Create the script: #!/bin/bash if [ $# …
This is post 12 of 19 in the series “[ Shell Scripting ]” The Bourne/bash shell supports a variety of conditionals, loops and other flow control operations. You’ll use these often. if The if statement is a simple conditional. Its syntax is: if condition ; then commands [elif condition ; then commands]… [else commands] fi …
This is post 11 of 19 in the series “[ Shell Scripting ]” Redirection Operators These operators redirect: standard input (0), standard output (1) and standard error (2). > redirects standard output to a file ps aux > file_name Creates a file and writes standard output. Clobbers any existing file. >> appends standard output to …
This is post 10 of 19 in the series “[ Shell Scripting ]” Any number of commands can be pipelined together. command1 | command2 The above command creates a pipe: the standard output of command1 is connected to the standard input of command2. Any command that can accept Standard Input and produce Standard Output is …
This is post 9 of 19 in the series “[ Shell Scripting ]” By default, every process has three associated file descriptors: standard input (0), standard output (1) and standard error (2). For these, Your keyboard is the default source of standard input. Your monitor is the default target for standard output, and Your monitor …