#Commands

## Files

Commands that can be used for reading and manipulating files

### tail

`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

`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

`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

`sed` is the '**S**tream **ED**itor' you can use to to modify files via commands and scripts using patterns, an [example](examples/seddnszone.md) 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

`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](/regex)|
| -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](/examples/grep)

### losof

`lsof` is a command that will show you what processes have specified file open currently you can see an example [here](/examples/lsof)

### rev