Common Unix commands¶

The Research Computing HPC server’s use Red Hat Enterprise Linux (RHEL) as the operating system. Many clusters around the world run exclusively Unix/Linux based operating systems. We strongly encourage users to actively get familiar with Unix command line interface and GNU/Linux in particular. Outstanding and Free documentation is provided at [http://www.tldp.org The Linux Documentation Project], specifically their [http://www.tldp.org/guides.html Guides] which cover basic topics including Using Linux and shell scripting to advanced File system and kernel modulization guides. Below is a succinct list of Unix commands that will help you get started in moving around and manipulating files.

Moving around the file system¶

pwd: List current directory
ls: List contents of current directory
ls -l: List contents of current directory with more information per file including permissions, last edited time, and size of file
ls -lh: Same as ls -lh except file size in included in ‘human readable’ form (gigabytes, megabytes, kilobytes)
ls -lt: Same as ls -l, except list files in chronological order with newer files occurring at the top
cd dirname: Changes current directory to dirname
cd ..: Changes current directory up one hierarchy level

Examining Files¶

cat <filename>: Concatenates filename and prints to standard output (screen)
less <filename>: A filter that pages through filename one full screen at a time. Allows both forward and backward movement through file
more <filename>: Similar to less, except cannot move backwards through file

Manipulating Files and Directories¶

cp <filename1> <filename2>: Copies filename1 to filename2. If filename2 is the name of a directory, copies filename1 into the directory
cp -i <filename1> <filename2>: Copies filename1 to filename2 and ask permission before overwriting
cp -r <directory1> <directory2>: Copies directory1 and all of it’s contents to directory2
mv <filename1> <filename2>: Renames ‘’filename1’’ to ‘’filename2’’. If ‘’filename2’’ is a directory, moves ‘’filename1’’ into directory
mv -i <filename1> <filename2>: Renames ‘’filename1’’ to ‘’filename2’’ and ask permission before overwriting files
rm <filename>: Removes file
rm -i <filename>: Removes file and ask permission before doing so
rm -r <directory>: Removes directory and it’s contents
rm -ir <directory>: Removes directory and it’s contents asking permission for each file
mkdir <directory>: Create a directory with ‘’directory’’ as a name
rmdir <directory>: Remove an empty directory