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Unix Command Cheat Sheet

Basic linux commands you need to know like breathing air

• ls - list the contents of the current directory
• pwd - print the present working directory  - tells you where you are currently. The format is something like /home/myID - just like on most computer systems, this represents leaves on the tree of the file system structure, also called a "path".
• cd <whereto> - change the present working directory to <whereto>  You will need to provide a path like /work/myID to change to that directory.
  • Some special <wheretos>: .. (period, period) means "up one level".   . means current directory. ~ (tilde) means "my home directory". ~myfriend (tilde "myfriend) means "myfriend's home directory".
• nano - The text editor we'll be using
• df shows you the top level of the directory structure of the system you're working on, along with how much disk space is available
• head <file> and tail <file> shows you the top or bottom 10 lines of a file <file>
• more <file> and less <file> both display the contents of <file> in nice ways. Read the bit above about man to figure out how to navigate and search when using less
• file <file> tells you what kind of file <file> is.
• cat <file> outputs all the contents of <file> - CAUTION - only use on small files.
• rm <file> deletes a file. This is permanent - not a "trash can" deletion.
• cp <source> <destination> copies the file source to the location and/or file name destination}. Using . (period) means "here, with the same name". * cp -r <dirname> <destination> will recursively copy the directory dirname and all its contents to the directory destination.
• scp <user>@<host>:<source> <destination> works just like cp but copies source from the user user's directory on remote machine host to the local file destination
• mkdir <dirname> and rmdir <dirname> make and remove the directory "dirname". This only removes empty directories - "rm -r <dirname>" will remove everything.
• wget <url> fetches a file with a valid URL. It's not that common but we'll use wget to pull data from one of TACC's web-based storage devices.
• man <unixcommand> displays the manual page for a unix command.
• >  is used to redirect STDOUT and STDERR to files.

Wildcards and special file names

The shell has shorthand to refer to groups of files by allowing wildcards in file names. * (asterisk) is the most common; it is a wildcard meaning "any length of any characters". Other useful ones are []to allow for any character in the set <characters>> 

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