A table of useful commands

Here are some useful commands - use man to get more information:

Command	What it does
hostname	What computer am I on?
pwd	What directory am I in?
mkdir	Create a new directory.
ls	List files in a directory, or a file or files you specify.
cp	Copy a file in a new location.
mv	Move a file to a new location (removing the original).
rm	Removes a file without asking for confirmation.
rmdir	Removes an entire directory. (Fails if the directory is not empty.)
touch	Changes the accessed and modified time on a file, by default to the current time. If the file doesn't exist, create a blank file.
which	Tells you where a command is on the filesystem.
cat	Show the contents of a text file.
head	Shows the first few lines of a file.
tail	Shows the last few lines of a file. You can combine head and tail using pipes to pull out a specific block of lines from a file.
less	Show the contents of a text file, interactively.
man	Use less to show the man page for a command.
wc	Counts the lines, words and letters in its input.
grep	Searches for a snippet of text in a file, showing matching lines.
cut	Print certain columns from a text file that's a table of data.
awk	Can do similar things to cut. It has its own language to specify in more detail how to process the file, which can be tough to learn, but it is more versatile than cut.
tr	Short for 'translate'. It lets you replace characters with other characters. This is useful to fix inconsistent data formats or remove characters that another tool can't handle.
sed	Short for 'stream editor'. Similar to tr, but it also supports more than single characters allowing for more complex replacements.
sort	Sorts the lines of a file.
uniq	Prints unique lines in a file (i.e. removing duplicates). It does not work exactly as you might expect, only removing duplicates on sequential lines. To get the truly unique output, you need to use sort first.
wget	Short for 'web get', this tool downloads a file from the internet, by default into the current directory.
curl -O	Downloads a file from the internet, by default into the current directory.
gzip	Compress a file (adding the .gz suffix)
gunzip	Decompress a gzipped file (removinf the .gz suffix)
tar	Collect up a directory structure into a single file, suitable for transfer
ssh	Securely log into a remote computer, based on the address you give it.
scp	Securely copy files from or to a remote computer.