| Command | Example | Works with
STDIN/OUT |
Function |
| ls | ls /tmp | Both | List files (like dir) |
| ls -l | ls -l /tmp | Both | List files long format |
| cp | cp src dest | None | Copies files |
| mv | mv oldname newname | None | Moves or changes the name of a file.
Cannot move a directory across between filesystems. |
| rm | rm oldfile | None | Deletes a file |
| rm -rf | rm -rf / | None | Deletes an entire subtree.
Can wipe out your whole hard drive!! |
| df | df | Out | Shows free disk space.
Shows all filesystems mounted |
| du | du /tmp | Out | Shows space used by a subtree
Requires permissions to read the subtree. Can be slow on big subtrees. |
| cd | cd | None | Change current dir to home dir. |
| cd | cd /tmp | None | Change current dir to given dir. |
| chmod | chmod a+rwx filename | None | Change permissions |
| chmod -R | chmod -R go-rwx . | None | Change permissions for a whole subtree. |
| chown | chown randy /home/randy | None | Change owner.
You must be root to use this command. Being the owner of the file is not enough! |
| chown -R | chown -R randy /home/randy | None | Changes a whole subtree. |
| less | less /tmp/README | In | Shows file to the screen. |
| grep | grep BUGS /tmp/README | Both | Shows lines containing the pattern to the screen. |
| grep -v | grep -v BUGS /tmp/README | Both | Shows lines NOT containing the pattern to the screen. |
| cat | cat file1 file2 | Both | Concatenates the files. |
| whoami | whoami | Out | Tells your current username. |
| su | su randy | None | Changes your current username.
requires a password for everyone except root. |
| time | time du /tmp | Out | Tells how long the command takes to run. |
| sort | sort /tmp/file-list | Both | Prints files in alphabetic order. (-r reverses order). |
| sort -n | sort -n /tmp/list-of-numbers | Both | Prints files in number order. (-r reverses order). |
| head | head -20 /tmp/list | Both | Prints only the first twenty lines. |
| tail | tail -20 /tmp/list | Both | Prints the last twenty lines. |
| gcc | gcc fred.c -o fred | None | Compiles the file fred.c into the executable fred |
| g++ | g++ fred.cc -o fred | None | Compiles the file fred.cc into the executable fred |
| ./command | ./fred | None | Runs the program you just compiled. |
| pico | pico fred.cc | None | Edit the program source code fred |
Commands can be combined.
To run commands consecutively, try separating them with a semi-colon.
ls; df; du
To run commands simultaneously, separate them with a '&'.
rm -rf /tmp & rm -rf /junk
To run commands and not wait for them to finish, end the command line
with a '&'.
rm -rf /junk &
To put the output of one command into the input of another, separate
them with a pipe.
ls | sort
To place the output of a command into a file, use a greater than symbol.
ls > file-list
To have a command read from a file, use a less-than symbol.
sort < file-list