Useful commands

From Linux 101, The beginner's guide to all things Linux.

This is a list of commands that are often overlooked by the common Linux user because these are such basic commands, yet we tend to use them fairly often.

cat <file> 

outputs the contents of file to standard output

date 

print or set the system time.

dd 

allows you to read from or write to a file with raw data. For example, you could use this to flood your entire harddrive with bits set to 0. You could also use this to read from a corrupt harddrive the raw data on it in an attempt to recover it.

echo 

allows you to echo, or write something to the standard output, or to a file if used in conjunction with the > or >> operators.

last, lastb 

shows the log of who connected to the system.

login, logout 

hmmmmmm ....

sh 

the standard command language interpreter used in scripts

tail [-f] <file> 

outputs the last few lines to standard output. -f option says to continue following file (if it were actively being written to like a system log.)

tee 

read from standard input and write to standard output and files.

touch 

updates (or changes) the file timestamps.

tr 

useful for translating a set of characters into another set (say all caps to lowercase) or even deleting a group of characters. See man page for details.

who 

shows who is connected to the system.