Difference between revisions of "Linux/C2/Simple-filters/English-timed"

| Here we will be learning about '''head, Tail, sort, cut''' and '''paste.'''

| We use the Head command followed by an '''ascii''' file name, to display the first 10 lines of a file by default.  

| Let us create a file. I am hitting on '''ESC''' (escape) key to show this practically.  

|Go to '''Applications > Accessories > Text Editor.'''

| Hit on '''File''' , '''Save.'''

|Name the file as '''numbers dot txt''' and hit on '''save'''

| Now go to '''Applications > Accessories > Terminal.'''

|Type '''ls''' and hit on '''enter.'''

|What we did here is to list all the folders and files on our '''home''' directory.  

| '''Cat n-u-m''' Hit on '''tab''' to autofill the file name. Hit on '''Enter.'''

| '''head numbers dot txt''', '''enter'''

| If we want to see the first 5 lines, use the option ''' hyphen n5''' in between the '''head''' command and the file.  

| Hit on Up arrow,  '''hyphen n5''' and '''Enter.'''

|'''F5'''

| The '''tail''' command works exactly opposite to the '''head''' command, it displays the last 10 lines of a file by default.

| I am hitting on '''ALT''' and '''Tab''' to switch to the terminal.

| '''tail numbers dot txt'''

| If we want to see just the last 5 lines, use the option '''hyphen n5''' in between the '''tail command''' and the file name.  

| '''hyphen n5''', '''Enter'''

| '''Auth dot log''' file maintains log's for who logged in & who logged out.

|'''tail hyphen f forward slash var slash log slash auth dot log'''

| Let us open another Terminal , '''Application- > Accessories - > Terminal.'''

|so that I can show you in a single screen how '''tail''' follows the last line in a '''log''' file.  

| Try to '''su''' as yourself, hit on '''enter.'''

| Give in some wrong password hit on '''enter.'''

| You will see that the terminal on which '''tail''' is running is appended with a new '''log.'''

|The date & time specifies when the '''authentication failure''' took place.  

| Type '''date''' hit on '''enter''' to verify the system date and time.

| Type '''Exit''' to close this terminal.

| Hit '''CTRL C''' to close the running tail command & maximize the screen.

| We have seen only '''auth dot log''' file in the previous example.

| '''Sort''' command as the name suggest will sort a file for us in both ascending and descending order.  

| '''sort numbers dot txt''' .This would sort our '''numbers dot txt''' file in ascending order.  

| Notice something is strange in there, sort just looks at the first character to sort, so '''10''','''11'''&'''12''' appears before the number 2.  

| To sort '''number dot txt''' in reverse order add an option of '''hyphen r.'''  

|'''U,  enter''',  

|Previously two 2's were displayed . Now only one 2 is displayed.

|Go to '''Applications > Accessories > Text Editor.'''

| I already have the data in another file for the sake of time constrain let me copy & Paste the value, '''CTRL+C; CTRL+V.'''

| File, Save it as '''marks dot txt''', Hit on '''Save.'''

| Let us sort based on the second column of '''marks dot txt file. '''

|'''sort space marks dot txt space hyphen t space open inverted commas space close inverted commas space'''

|here '''hyphen t''' stands for the '''delimiter''' & the space in between the quotes represents it.  

|'''hyphen k2''' for the second column on which sort should be performed.

|Hit on '''Enter.'''

|'''Cat marks dot txt'''

|This is the original file, if you see '''Avir''' is moved above and '''Bala''' came below when we sorted based on the second column alone.  

|'''Cut''' command is used to cut just certain information from a file.  

|Let us pull out the names from '''marks dot txt'''

|Let us go to the terminal '''ALT Tab'''

|'''cut space marks dot txt space hyphen d space open inverted commas  space close inverted commas space.'''

|here in '''cut''' command '''d''' is the delimiter & the space inbetween the quotes represents the delimiter.

|'''hyphen f2''' for the second column. Hit on '''enter.'''

|'''Paste''' command will merge corresponding subsequent lines of the files.  

| Let us use both the '''numbers dot txt''' and '''marks dot txt file''' now.  

|'''Paste numbers dot txt marks dot txt''', '''enter'''

|Now the first line of '''marks dot txt was appended to the first line of numbers dot txt.  

|We can use the redirect key to redirect this output to some other file called '''concatefile dot txt. '''

| Hit on Up arrow. Hit on the redirect key which is the Greater than symbol '''concatfile dot txt'''. Hit on '''Enter.'''

| '''Cat concatfile dot txt'''

| '''Paste  hyphen s'''

|'''numbers dot txt'''