Commands

Manipulating files

Commands that can be used for reading and manipulating files

tail by default reads the last 5 lines of the input file and then exits

Useful Flags	Function
-n x	Returns the last x lines of a file
-f	Follows the end of the file, so any new data will be printed out to the screen

head by default reads the first 5 lines of the input file and then exits

Useful Flags	Function
-n x	Returns the first x lines of a file

awk is used to extract, layout and modify data using the command line (It is way more then this but its all I use it for)

sed is the 'Stream EDitor' you can use to to modify files via commands and scripts using patterns, an example can be seen here

Useful Flags	Function
-i	In-place, writes the changes to the file
-f	Use a script file instead of reading the expression from STDIN

grep is used to match text in a file,

Useful Flags	Function
-o	Returns only the matched data (Useless without regex really)
-E	Allows extended regex to be used in the search, regex info
-P	Allows the use of Perl regex, this uses a different syntax to -E
-i	Makes the search case insensitive
-r	Searches files recursively (i.e if you have quite a few files and folders it will search through all of them)
-l	Returns the filename where the data was matched instead of the matched data

Some examples of grep usage can be found here

lsof is a command that will show you what processes have specified file open currently you can see an example here

These commands can be used to manipulate data in the standard input