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File System in UNIX

File System in UNIX. Files and Directories in UNIX. The first file in UNIX file system is “root” or “/”. Files and Directories in UNIX (continue.). Home directory (could be named differently) has subdirectory per user called “User Home Directory”

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File System in UNIX

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  1. File System in UNIX

  2. Files and Directories in UNIX • The first file in UNIX file system is “root” or “/”

  3. Files and Directories in UNIX (continue.) • Home directory (could be named differently) has subdirectory per user called “User Home Directory” • Directories can have more subdirectory and files • A file or a directory can be referred to by • Relative path name [a.doc if you are at Documents] • Absolute path name [/home/abuzneid/UNIX/Documents/a.doc}\] • File and directory names are case sensitive

  4. Files and Directories in UNIX (continue.) • To display working directory $ pwd /home/abuzneid/UNIX $ • cd command to change directory $ ls -l total 8 drwxr-xr-x 2 abuzneid 534 512 Oct 8 13:40 Documents drwxr-xr-x 2 abuzneid 534 512 Oct 8 13:43 mail drwxr-xr-x 2 abuzneid 534 512 Oct 8 13:53 memos drwxr-xr-x 2 abuzneid 534 512 Oct 8 13:53 personal $ cd Documents $ pwd /home/abuzneid/UNIX/Documents $

  5. Files and Directories in UNIX (continue.) $ pwd /home/abuzneid/UNIX $ ls -l total 8 drwxr-xr-x 2 abuzneid 534 512 Oct 8 13:40 Documents drwxr-xr-x 2 abuzneid 534 512 Oct 8 13:43 mail drwxr-xr-x 2 abuzneid 534 512 Oct 8 13:53 memos drwxr-xr-x 2 abuzneid 534 512 Oct 8 13:53 personal $ cd Documents $ pwd /home/abuzneid/UNIX/Documents $ cd .. $ pwd /home/abuzneid/UNIX $

  6. Files and Directories in UNIX (continue.) $ cd / $ pwd / $ cd /home/abuzneid/UNIX/Documents $ pwd /home/abuzneid/UNIX/Documents $ cd ../.. $ pwd /home/abuzneid $ cd $ pwd /home/abuzneid $

  7. List Files • ls command is used to list files and directories • ls –l displays more information about every file and directory • file type • d for directory • - for file • b, c, p for special file • access made for the owner, group and others • number of links • owner of the file • Size • last modification • file name

  8. List Files (continue.) $ pwd /home/abuzneid/UNIX/Documents $ ls a.doc c.doc $ ls -l total 4 -rw-r--r-- 1 abuzneid 534 14 Oct 8 13:37 a.doc -rw-r--r-- 1 abuzneid 534 14 Oct 8 13:38 c.doc $ cd $ pwd /home/abuneid $ ls UNIX Documents mail memos personal $

  9. List Files (continue.) $ ls -a . .. Documents mail Memos personal $

  10. Creating a Directory: the mkdir command • mkdir command $ pwd /home/abuzneid/UNIX $ mkdir test $ ls Documents mail Memos personal test $ cd test $ pwd /home/abuzneid/UNIX/test $

  11. Copying file from directory to another $ cp UNIX/personal/p1 UNIX/Documents/p11 $ ls UNIX/Documents a.doc c.doc p11 $ cp UNIX/personal/p1 UNIX/Documents $ ls UNIX/Documents a.doc c.doc p1 p11 $ cd UNIX/personal $ pwd /home/abuzneid/UNIX/personal $ ls p1 p2 $ cp p1 p2 /home/abuzneid/UNIX/mail $

  12. Moving Files between Directories $ cd /home/abuzneid/UNIX/personal $ ls -l total 4 -rw-r--r-- 1 abuzneid 534 11 Oct 10 21:46 p1 -rw-r--r-- 1 abuzneid 534 11 Oct 10 21:49 p2 $ mv p1 p2 /home/abuzneid/UNIX/Memos $ cd /home/abuzneid/UNIX/Memos $ ls p1 p2 $

  13. Rename File or Directory • mv is used to rename a file of a directory $ ls -l total 14 drwxr-xr-x 2 abuzneid 534 512 Oct 10 21:47 Documents drwxr-xr-x 2 abuzneid 534 512 Oct 8 13:43 mail drwxr-xr-x 2 abuzneid 534 512 Oct 10 21:54 Memos drwxr-xr-x 2 abuzneid 534 512 Oct 8 23:42 memos drwxr-xr-x 2 abuzneid 534 512 Oct 10 21:54 personal drwxr-xr-x 2 abuzneid 534 512 Oct 8 23:42 TEST drwxr-xr-x 2 abuzneid 534 512 Oct 10 21:39 test $ mv Memos memos $

  14. Rename File or Directory (continue.) Memos renamed to memos $ ls -l total 12 drwxr-xr-x 2 abuzneid 534 512 Oct 10 21:47 Documents drwxr-xr-x 2 abuzneid 534 512 Oct 8 13:43 mail drwxr-xr-x 3 abuzneid 534 512 Oct 10 21:57 memos drwxr-xr-x 2 abuzneid 534 512 Oct 10 21:54 personal drwxr-xr-x 2 abuzneid 534 512 Oct 8 23:42 TEST drwxr-xr-x 2 abuzneid 534 512 Oct 10 21:39 test $

  15. Removing a directory: the rmdir command • To remove a directory: • rmdir <directory name> if the directory is empty • rm –r <directory name> if it’s not empty

  16. Removing a directory: the rmdir command (continue.) $ rmdir /home/abuzneid/UNIX/memos rmdir: directory "/home/abuzneid/UNIX/memos": Directory not empty ALL SUBDIRECTORIES AND FILES IN memos MUST BE DELETED FIRST $ cd /home/abuzneid/UNIX/memos $ ls -l total 4 -rw-r--r-- 1 abuzneid 534 11 Oct 8 23:23 p1 -rw-r--r-- 1 abuzneid 534 11 Oct 8 23:29 p2 $ rm * $ ls $ cd .. $ rmdir memos $ ls -l total 10 drwxr-xr-x 2 abuzneid 534 512 Oct 10 21:47 Documents drwxr-xr-x 2 abuzneid 534 512 Oct 8 13:43 mail drwxr-xr-x 2 abuzneid 534 512 Oct 10 21:54 personal drwxr-xr-x 2 abuzneid 534 512 Oct 8 23:42 TEST drwxr-xr-x 2 abuzneid 534 512 Oct 10 21:39 test $

  17. Linking Files: the ln command • To have two copies of any file, you can use: • cp to copy it to another file, or • ln to link the file to another file • The disadvantages of cp • Consumes twice as much disk space • Both files always has to be changed if any of them is updated to keep them identical • Number of links to a file is, normally 1 for non-linked, non-directory files • More than one link to a file is possible • Most often, ln is used to link files between directories

  18. Linking Files: the ln command (continue.) • There is two types of links

  19. Linking Files: the ln command (continue.) $ cat aaa Bridgeport Massashusets New Hampshire Vermont $ ls -l total 12 -rw-r--r-- 1 abuzneid 534 46 Oct 10 23:14 aaa -rw-r--r-- 1 abuzneid 534 34 Oct 10 23:12 bbb drwxr-xr-x 2 abuzneid 534 512 Oct 10 21:47 Documents drwxr-xr-x 2 abuzneid 534 512 Oct 8 13:43 mail drwxr-xr-x 2 abuzneid 534 512 Oct 10 21:54 personal drwxr-xr-x 2 abuzneid 534 512 Oct 8 23:42 TEST drwxr-xr-x 2 abuzneid 534 512 Oct 10 21:39 test $

  20. Linking Files: the ln command (continue.) $ ln aaa bbb $ ls -l total 14 -rw-r--r-- 2 abuzneid 534 46 Oct 10 23:14 aaa -rw-r--r-- 2 abuzneid 534 46 Oct 10 23:14 bbb drwxr-xr-x 2 abuzneid 534 512 Oct 10 21:47 Documents drwxr-xr-x 2 abuzneid 534 512 Oct 8 13:43 mail drwxr-xr-x 2 abuzneid 534 512 Oct 10 21:54 personal drwxr-xr-x 2 abuzneid 534 512 Oct 8 23:42 TEST drwxr-xr-x 2 abuzneid 534 512 Oct 10 21:39 test $ cat bbb Bridgeport Massashusets New Hampshire Vermont $

  21. Linking Files: the ln command (continue.) $ echo one more line >> aaa $ cat aaa Bridgeport Massashusets New Hampshire Vermont one more line $ cat bbb Bridgeport Massashusets New Hampshire Vermont one more line $ rm aaa $ cat bbb Bridgeport Massashusets New Hampshire Vermont one more line $

  22. Linking Files: the ln command (continue.) $ cp bbb ccc $ ln -s ccc ddd $ ls -l total 16 -rw-r--r-- 1 abuzneid 534 60 Oct 10 23:20 bbb -rw-r--r-- 1 abuzneid 534 60 Oct 10 23:25 ccc lrwxrwxrwx 1 abuzneid 534 3 Oct 10 23:26 ddd -> ccc drwxr-xr-x 2 abuzneid 534 512 Oct 10 21:47 Documents drwxr-xr-x 2 abuzneid 534 512 Oct 8 13:43 mail drwxr-xr-x 2 abuzneid 534 512 Oct 10 21:54 personal drwxr-xr-x 2 abuzneid 534 512 Oct 8 23:42 TEST drwxr-xr-x 2 abuzneid 534 512 Oct 10 21:39 test $ rm ccc $ cat ddd cat: cannot open ddd $

  23. File Name Substitution $ ls bbb ddd Documents mail personal TEST test $ echo * Documents TEST bbb ddd mail personal test $ echo *.* *.* $ echo a* a* $ echo m* mail $ echo *a* mail personal $ • The asterisk ”*”: substitutes zero or more characters

  24. File Name Substitution (continue.) • “?” matches single character $ ls bbb ddd Documents mail personal TEST test $ echo ??? bbb ddd $

  25. File Name Substitution (continue.) • Matching a single character using square brackets [] • [abc] matches one letter • [!a-z] matches any character except a lower case letter • *[!X] matches any file that doesn't end with the upper case X

  26. standard input standard output command Standard Input/Output • Standard input is the terminal (keyboard) • Standard output is the terminal (display)

  27. skan tty01 Jan 07 07:56 wiem tty52 Jan 07 06:15 samir tty03 Jan 07 09:26 who Standard Input/Output (continue.) • If a sort command is executed without a file name argument, then the command will take its input from standard input

  28. Standard Input/Output (continue.) • Example: $ sort nouha mahdi malek issam salwa issam mahdi malek nouha salwa $

  29. skan wiem samir skan wiem samir sort Standard Input/Output (continue.)

  30. Output Redirection • Output directed to a file instead of standard output • command > ofile directs output to the file ofile • command >> ofile appends output to the file ofile • > ofile creates an empty file “ofile”

  31. Output Redirection (continue.) • Example: $ who > users $ cat users bgeorge pts/16 Oct 5 15:01 (216.87.102.204) abakshi pts/7 Oct 10 22:56 (216.87.102.210) abuzneid pts/9 Oct 10 19:29 (avicenna.102.87.216.in-addr.arpa) xiafeng pts/10 Oct 10 23:16 (Shiva-RAS-Pool-13.uhmc.sunysb.edu) $ echo add one more line >> users $ cat users bgeorge pts/16 Oct 5 15:01 (216.87.102.204) abakshi pts/7 Oct 10 22:56 (216.87.102.210) abuzneid pts/9 Oct 10 19:29 (avicenna.102.87.216.in-addr.arpa) xiafeng pts/20 Oct 10 22:11 (Shiva-RAS-Pool-53.uhmc.sunysb.edu) xiafeng pts/21 Oct 10 22:15 (Shiva-RAS-Pool-55.uhmc.sunysb.edu) xiafeng pts/10 Oct 10 23:16 (Shiva-RAS-Pool-13.uhmc.sunysb.edu) add one more line $ > users $ cat users $

  32. Input Redirection • Input of a file is redirected from a file • command < infile get the input from the file infile • Example: $ who > users $ wc -l users 15 users $ wc -l < users 15 $

  33. Pipes • Connects the output of one command to the input of another command • Example: $ who | wc -l 14 $ ls | wc -l 8 $

  34. who wc -l 5 Pipes (continue.)

  35. Filters • Any program that can take input from standard input, perform some operation on that input, and write the results to standard output • Example: cat and sort are filters

  36. Standard Errors • Terminal is the standard error • In most cases, you never know the difference between standard output and standard error • command 2> efile directs the error to the file efile

  37. Standard Errors (continue.) • Examples: $ ls n* n*: No such file or directory $ ls n* > foo n*: No such file or directory $ ls 2> foo bbb Documents mail TEST users ddd foo personal test $ cat foo

  38. References • UNIX SHELLS BY EXAMPLE BY ELLIE QUIGLEY • UNIX FOR PROGRAMMERS AND USERS BY G. GLASS AND K ABLES • UNIX SHELL PROGRAMMING BY S. KOCHAN AND P. WOOD

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