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” 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

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

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

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 $

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

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

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

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 $

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 $

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

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

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

Removing a directory: the rmdir command To remove a directory: rmdir if the directory is empty rm –r if it’s not empty

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 Oct 8 23:23 p1 -rw-r--r-- 1 abuzneid Oct 8 23:29 p2 $ rm * $ ls $ cd.. $ rmdir memos $ ls -l total 10 drwxr-xr-x 2 abuzneid Oct 10 21:47 Documents drwxr-xr-x 2 abuzneid Oct 8 13:43 mail drwxr-xr-x 2 abuzneid Oct 10 21:54 personal drwxr-xr-x 2 abuzneid Oct 8 23:42 TEST drwxr-xr-x 2 abuzneid Oct 10 21:39 test $

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

Linking Files: the ln command (continue.) There is two types of links Hard diskSoft link ln “to” can be file or directory “to” and “from” must resides on the same file system “to” and “from” may resides on different file system “to” and “from” will have the same size “to” will have a size of link (pointer) to “from” If “to” is deleted “from” will work fine and vice versa If “from” is deleted, “to” will not work

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

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

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 $

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

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

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

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

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

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 who skantty01 Jan 07 07:56 wiemtty52 Jan 07 06:15 samirtty03 Jan 07 09:26

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

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

Output Redirection Output directed to a file instead of standard output command > ofiledirects output to the file ofile command >> ofile appends output to the file ofile > ofilecreates an empty file “ofile”

Output Redirection (continue.) Example: $ who > users $ cat users bgeorge pts/16 Oct 5 15:01 ( ) abakshi pts/7 Oct 10 22:56 ( ) abuzneid pts/9 Oct 10 19:29 (avicenna 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 ( ) abakshi pts/7 Oct 10 22:56 ( ) abuzneid pts/9 Oct 10 19:29 (avicenna 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 $

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

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

Pipes (continue.) wc -l 5 who

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

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

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

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