UNIX Commands

Introduction

Managing files (copying, renaming, moving, removing, etc.) are common tasks. Although there are GUI ways to do these things, doing them from the command line is often quicker.

The shell (command interpreter) maintains a current directory. The current directory is the directory you are currently "in". This can be changed with the cd command.

Many commands work relative to the current directory.

When you first login, the directory that you are in is your home directory.

Folders in UNIX/Linux (just UNIX from here on) are called directories.

# indicates a comment and is not a part of the command.

Paths

Specifying paths:

There are two ways to specify where a file or directory is:

absolute path - The path begins with "/" and specifies the sequence of directories to the desired file or directory.
relative path - The path doesn't begin with "/". For "." and "..", the path starts relative to the current directory.

In UNIX, "/" is the top of the file system, like the C: drive in Windows. Unlike Windows, there are no other drives, all is integrated under "/".
Note that "/" alone, the first "/" in a path, is a directory, called the root directory. The "/" is also used as a separator to separate directories and files in a path.
"." may be used in a path specification, it denotes the current directory.
".." may be used in a path specification, it denotes the parent of the current directory, the one before the current directory in the path to the current directory.
"~" may begin a path specification, it denotes a user's home directory.
"~username" may begin a path specification, it denotes username's home directory.

Notes

For the commands below:

bold, monospace indicates a UNIX command, possibly with options.
Options may follow a command name and begin with a "-". Often (in UNIX) options denoted by a single character may be grouped together. An option modifies the behavior of the command.
italics indicates arguments to the command. These are user supplied files, directories, etc. as appropriate.
[optional items], square brackets, [ ], indicate optional items, they may be omitted or included.
Look at the manual entry for a command (man command, ex: man ls) for more details.

List Commands

`ls`		List the files in the current directory.
`ls -l`		List the files in the current directory with additional info.
`ls -al`		List ALL the files in the current directory with additional info. Files whose names begin with a "`.`" are not listed by default.
`ls [options] path`		List the files in the directory specified by path. path may be absolute or relative, options may eb the above options or others.

Moving Around Commands

`cd`		Change the current directory to your home directory.
`cd path_to_directory`		Change the current directory to directory path_to_directory. path_to_directory may be absolute or relative
`pwd`		"print working directory", "present working directory", shows your current working directory.

File Commands

`cp file1 file2`		An identical copy of file1 is made and named file2.
`mv file1 file2`		File file1 is renamed (moved) to file2
`rm file`		File file is deleted (removed)

The commands cp, mv, and rm all may delete a file.

The destination file, file2, in the case of cp and mv is overwritten and the old content is lost.

A DELETED FILE IS UNRECOVERABLE. Be careful with these commands.

If a file is under version control, the svn commands must be used.

Directory Commands

`mkdir dir`		Create directory dir in the current directory. You may want to give directories a name which begins with an uppercase letter, so they stand out.
`rmdir dir`		Remove directory dir in the current directory. If the directory is not empty it will not be removed.

Note that if a directory is under version control, the svn> commands must be used

File Commands

wc

Word count, show count of characters, words, and lines.

wc file

wc -l *.h *.cpp # Line count for only all .h and .cpp files

Examples

cd /                 # Change directory to the root directory

cd /usr/include      # Change directory to /usr/include

cd ..                # Change directory to parent directory

cd Dir1              # Change directory to Dir1 in current directory

cd ../Dir2           # Change directory to Dir2 in parent directory

ls ..                # List files in parent directory

ls ../../lecture     # List files in directory lecture in parent's parent

ls ~                 # List files in your home directory

ls ~/Dir             # List files in Dir which is in your home directory

mv -i file1 file2    # Interactive, ask for confirmation

rm -i file           # Interactive, ask for confirmation

Changing directories to nonexistent directories or listing nonexistent items will produce an error message.

URL: https://data-structures.cs.kent.edu/labs/Info/unix_files.html
Last update: EST