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Unix Basics

Unix Basics. Systems Programming Concepts. Unix Basics. Unix directories Important Unix file commands man, pwd , ls , mkdir , cd, cp , mv File and directory a ccess r ights through p ermission settings Using chmod to change permissions Other important Unix commands

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Unix Basics

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  1. Unix Basics Systems Programming Concepts

  2. Unix Basics • Unix directories • Important Unix file commands • man, pwd, ls, mkdir, cd, cp, mv • File and directory access rights through permission settings • Using chmodto change permissions • Other important Unix commands • emacs, cat, rm, ps, kill Systems Programming Unix Basics

  3. Unix File Structure • Hierarchical file system • File System starts at root, denoted “/”. • Abstraction is to navigate through the Unix directory structure relative to the current “working” directory. • Slashes separate directory levels. • File names cannot have blanks and lower-case is preferred {case-sensitive}. • Extensions are just conventions to the file system, but NOT to compilers! Systems Programming Unix Basics

  4. Unix File Notation . = the current directory ..= the parent directory ~= my home directory (i.e., the current directory when I login) File name wild cards ? = any one character * = any zero or more characters Systems Programming Unix Basics

  5. Unix Commands • Basic format: Command –option parameters ls –l labs* cp old.cnew.c • Unix commands can be cryptic and many are only two characters long, but an important exception is: man= manual page request man ls Systems Programming Unix Basics

  6. Commands: pwd & ls pwd = print working directory ls = list file names and attributes. -l = long listing -d = list directory itself, not contents -a = all files (including starting with “.”) ls[just file names] ls –la [lots of info!] ls –la labs* [only info on labs files] ls –d [just directory names] Systems Programming Unix Basics

  7. Commands: mkdir & cd mkdir= make a new directory mkdirnewdir cd = change directory cdnewdir cd ../updir cd [change to home directory] Systems Programming Unix Basics

  8. Commands: mv & cp cp = copy file cp source destination -p= preserve permissions cp –p old.cnew.c cp prog1.c prog_dir/ cp *.c prog_dir/ mv = move file mv source destination mv prog1.c distance.c mv prog1.c prog_dir/ For both commands if the destination is an existing directory, the file name stays the same. Systems Programming Unix Basics

  9. File and Directory Permissions • Each file or directory has three sets of permissions: • User (i.e. owner) • Note - Only the user can change permissions. • Group (e.g., cs2303 ) • Other (the world!) • Each permission set has three permissions: • Read • Write • Execute These are visible left to right via: ls –la Systems Programming Unix Basics

  10. File and Directory Permissions • Read access= You can read the file contents. You can list the contents of the directory. • Write access = You can write into this file. You can modify this directory. • Execute access = You can run this file as a command. You can use this directory as part of a path. To access any file, you first need execute permission on all directories from the root to the file. Systems Programming Unix Basics

  11. Command: chmod chmod = Change mode (permissions) chmod mode files mode: specify users: u, g, o anda (for all) specify attribute: r, w, or x connect with action: + = add - = delete = = set Systems Programming Unix Basics

  12. Command: chmod • Examples: chmod u+x prog4.cpp chmod o-r prog4.cpp chmod u=rwx prog4.cpp chmod o+r,g+r prog4.cpp • You can also use octal numbers: chmod 700 prog2.c chmod 750 sample.c Systems Programming Unix Basics

  13. Commands: emacs, cat, more command filename {generic format} emacsused to edit a file emacs lab1.c catprints text file to stdout cat lab1.c moreprints text file (only fill one screen) more lab1.c hit the space bar to see more or q to quit. Systems Programming Unix Basics

  14. Commands: rm, ps, kill rm= delete a file rm olddat.txt ps= print currently active processes ps kill = stop one of your running processes kill -9 26814 Systems Programming Unix Basics

  15. Example: ps kill $emacssimple.c {inside edit of simple.c} ^z $ps PID TTY TIME CMD 26792 pts/17 00:00:00 tcsh 26814 pts/17 00:00:00 emacs 26815 pts/17 00:00:00 ps $ kill -9 26814 $ [1] Killed emacssimple.c type % to resume Systems Programming Unix Basics

  16. Review of Unix Basics • Unix directories • Important Unix file commands • man, pwd, ls, mkdir, cd, cp, mv • File and Directory Access Rights through Permission Settings • Using chmodto change permissions • Other important commands • emacs, cat, rm, ps, kill Systems Programming Unix Basics

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