Unix

File and Directory Names

• /, rather than \ for path separator, so it's home/weiss, NOT \home\weiss
• ? matches any single character — program_?.cpp matches program_1, program_a, program_!,
• * matches any sequence of characters — program_*.cpp matches program_1.cpp, program_original.cpp, program_.cpp
• $HOME, ~ - your home directory
  • cd ~/public_html
• ~username - username's home directory
  • cd ~weiss/private
• . - current directory
• .. - parent directory

Absolute and Relative Paths

• A file's path is the set of directories leading from the topmost directory to the one containing the file itself. Thus if the file is /home/weiss/private/Programs/Lecture01/hello.cpp, then the file (hello.cpp) has the path /home/weiss/private/Programs/Lecture01.
• Paths may be specified in an absolute by specifying the full sequence from the topmost (root) directory. This is done by beginning the path with a /. This is known as an absolute path. Thus, the absolute path /home/weiss/public_html refers to starting at the topmost directory, moving into the home directory; from there moving to the weiss directroy and finally to the public_html directory.
• In the second method of specifying directories, paths are specified relative to the current directory, i.e., the directory you are currently in. Such relative paths do no begin with a / and their startiing location is the current directory. Thus, the path Programs/Lecture02 means than one move from the current directory to the directory named Programs and from there to the Lecture02. Furthermore, if our current directory were /home/weiss/private then the absolute path of the above would be /home/weiss/private/Programs/Lecture02.
• Relative paths often make use of the .. symbol for the parent directory (which is in some respects, itself a relative path) — it allows one to move up the directory structure (without having to know the actual name of the parent directory). Thus if the current directory is /home/weiss/private then the path ../../arnow/public_html (up a directory -- to /home/weiss, up a second directory -- to /home; then down to /home/arnow, and down again to /home/arnow/public_html.
• Finally, the ~ and ~username notations allow one to begin relative paths at one's own home directory or another user's.

Working with Directories

• cd dirname - changes current directory to dirname
• cd - changes current directory to your home directory
• mkdir dirname - creates directory dirname
• rmdir dirname - deletes directory dirname (must be empty)