Difference between revisions of "Linux/C2/General-Purpose-Utilities-in-Linux/English-timed"

|Hi, welcome to this spoken tutorial on General Purpose Utilities in Linux.

|In this tutorial we will make ourselves acquainted with some of the most basic yet heavily used commands of Linux.  

|The main motivation of this is to give you a headstart about working with Linux.  

|The first command that we will see is the echo command. However note that linux commands are case sensitive.

|Here all commands and their options are in small letters unless otherwise mentioned.

|Ctrl Alt t helps to start a terminal in ubuntu.

|This command may not work in all unix systems however.

|Type at the prompt echo space Hello World and press enter.

|This prints the customary Hello World message on the screen.  

|We can also use the echo command to display the value of a variable.

|Type at the prompt echo space dollar SHELL in capital and press enter

|This outputs the present shell being used.

|We can also use escape sequences with echo command.

| For this in Linux we need to use the -e (hyphen e) option.  

|Common escape sequences include \t (backslash t) for tab, \n for new line and \c is a escape sequence which when used causes the prompt to be displayed on the same line.  

|This can be useful if say we want a prompt message before entering something.  Type at the prompt

echo space minus e within single quote  

Enter a command back slash c and press enter.

|We will see that the prompt will be displayed after printing ‘enter a command ‘on the same line.

|To know this and many other characteristics of our machine we have the uname command.Type at the prompt uname space hyphen r and press enter .

|To know what is your username, type at the prompt who space am space I and press enter.

| This in fact comes from the who command that enlists all the users currently logged into the system in case your system is a multiuser system.  

|For this we have the passwd command. Type at the prompt

p-a-s-s-w-d and press enter

|When that is correctly entered ,you will have to enter your new password and then retype it to confirm.  

|Then also the password can be changed without knowing the current password, but that can only be done by the root user.  

|Now who is a root user?  

|To draw an analogy we can say a root user is similar to a user in Windows with Administrator status.  

|We may be interested in knowing the system date and time. For this we have the date command.  

|Type date in the terminal and press enter

|Type at the prompt date space plus 'percent' sign capital T and press enter.

| Type at the prompt date space plus 'percentage sign small h and press enter.

| It gives the name of the month

|Type at the prompt, date space plus percentage sign small m and press enter.

| Type at the prompt date space plus percentage sign small y and press enter .

| We can combine these options as well. For example type at the prompt date space plus within double quotes percentage small h percentage small y and press enter .

|Another related command is the cal command. Though not as common this helps you to see the calender of any month and any year.

| To see the current months calendar type at the prompt ‘cal’ and press enter.

|To see the calendar of any arbitrary month say december 2070 type at the prompt ‘ cal space 12 space 2070 and press enter.

|This gives the calendar of December 2070

|A directory helps us in organising our files in a systematic manner .  

| When we login into the Linux system we are by default in a home directory. To see the home directory type at the prompt echo space dollar HOME in capital and press enter.

|The next command helps us to see the directory we are currently working in. It is pwd that stands for present working directory. Type at the prompt pwd and press enter.

|Once we know of our directory we would also want to know what are the files and subdirectories in that directory. For this we have the ls command which is probably the most widely used command in Unix and Linux.  

|Type the command ls and press enter.  

|Files and subdirectories are generally shown with different colours.  

|ls is a very versatile command and has many options. Let us see some of them, Type at the prompt ls  space  minus minus all and press enter.

|This shows all the files including the hidden files(hidden files here are filenames starting with dot (.))  

|If we not only want to see the file but also get more information we can use the minus l option.  

|Just type the command ls space minus small l and press enter.

|It gives us the file permissions, file owner's name, last modification time,file size in bytes etc. Explanation of the fields of this option is beyond the scope of the present tutorial.

|Just type the command followed by the right angle bracket and the file name. Say we write ls space minus small l space right angle bracket space fileinfo and press enter.

|Now all the files and directories information will be directed into the file named fileinfo.

|But how do we see the content of this file? For this we have the cat command. Just type cat space and the name of the file , here it is fileinfo and press enter.

|Now you can see its contents. Infact the other main use of cat is to create a file. For this type at the prompt cat space right angle bracket space filename say file1 and press enter.

|Now when we press enter the command waits for input from the user.

|Now press enter key to indicate the end of input.

|Now press the Ctrl and D keys together.

|If a file by name say file1 already exist then the user input will be overwritten on this file.

|Now if you wish to append to the end of an existing file ‘file1’ type at the prompt cat space double right angle bracket space file1 and press enter.

|There are several other commands that we could have discussed but we would keep it to this for now. Infact even for all the commands discussed there are many options and possibilities untouched here.

|This brings us to the end of this spoken tutorial.Spoken Tutorials are a part of the Talk to a Teacher project, supported by the National Mission on Education through ICT.