1. 7/17/2009 rwjBROOKDALE COMMUNITY COLLEGE1 Unix Comp-145 C HAPTER 2

2. 7/17/2009 rwjBROOKDALE COMMUNITY COLLEGE2 Objectives U NIX C OMMANDS T HE P ATH F LEXIBILITY OF C OMMAND U SAGE A CCESS AND M ANIPULATE F ILES C OMMAND C LASSIFICATION U SING MAN S EVERAL SIMPLE COMMANDS

3. UNIX Commands WHO ( LISTS WHO IS ON SYSTEM ) DATE ( DATE AND TIME ) MAN ( MANUAL PAGE FOR THE SPECIFIED COMMAND ) INFO - LIKE MAN ORGANIZED HIERARCHICALLY PASSWD ( CHANGE PASSWD ) SCRIPT - LOGS ALL INTERACTION IN A FILE CLEAR - CLEAR SCREEN TTY - TERMINAL ID STTY - TERMINAL OPTIONS EXIT – T ERMINATE SESSION

4. UNIX Commands G ENERALLY, COMMANDS ARE EXECUTABLE DISK FILES (C PROGRAMS ) – Commands execute like any other program (remember chp 1) – UNIX supports commands written in any language (ie Java) – Files do not need extension – Shell (exception) automatically invoked once you log in

5. Types of Commands I NTERNAL COMMAND OF THE SHELL WHICH COULD BE a built-in (like cd, pwd, etc.) an alias defined by the user that invokes the disk or E XTERNAL PROGRAM ON DISK WHICH COULD BE a binary executable (written in C, C++). a script file (like a shell or perl script). internal version in a specific manner.

6. The PATH A shell variable (or environment variable) o Specifies a list of directories to search. Shell looks at PATH only when o Command is not used with a pathname o Also not a shell built-in. Command can still be executed if not in PATH by o Using a pathname. o Modifying PATH to include the directory containing the command. 7/17/2009 rwjBROOKDALE COMMUNITY COLLEGE6

7. 7/17/2009 rwjBROOKDALE COMMUNITY COLLEGE7 The PATH (Contd) PATH can be modified in an absolute or relative manner: PATH =/usr/bin:. (Absolute) PATH=$PATH:/usr/local/bin (Relative) Modified setting is lost after user has logged out unless saved in a startup file.

8. Flexibility of Command Usage Run multiple commands by specifying them in the same line: date ; echo $PATH Split a command into multiple lines: $ echo “Hello > Dolly” Save command output in a file: date > foo date | cut -d” “ -f2 7/17/2009 rwjBROOKDALE COMMUNITY COLLEGE8

9. 7/17/2009 rwjBROOKDALE COMMUNITY COLLEGE9 Flexibility of Command Usage (Cont’d) Use output of one command as input of another: date | cut -d” “ -f2 Run a command in the background with &: ls -lRa / > $HOME/ls-lRa.txt &

10. Access and Manipulate Files ls - List directory content mv – Move file to another location or name cp - Create a copy of the named file in the current or different directory mkdir – Create a new directory as a child of the current directory rm – Remove the named file rmdir – Remove the named directory 7/17/2009 rwjBROOKDALE COMMUNITY COLLEGE10

11. Command Classification: A Different Approach Utilities that are generally used in standalone mode ( vi, stty, bc ). Commands that do useful work but produce no output ( mkdir, cp, rm ). Commands that produce output which may need further processing ( date, who, ls, tty, man, info ). Commands specially designed to accept output of other commands as their input and vice versa ( grep, sort, head, prt ). 7/17/2009 rwjBROOKDALE COMMUNITY COLLEGE11

12. Using man Displays documentation of commands, configuration files, system calls and library functions. Organized in a number of sections. Commands are found in Section 1. May need to use section number when entry exists in multiple sections (e.g. man passwd and man -s 5 passwd ). 7/17/2009 rwjBROOKDALE COMMUNITY COLLEGE12

13. 7/17/2009 rwjBROOKDALE COMMUNITY COLLEGE13 Using man (Cont’d) man documentation not available for most internal commands of the shell. Use man man first to know how man should be used.

14. Understanding a man Page Example: wc Syntax/Synopsis wc [ -c | -m | -C ] [ -lw ] [ file... ] Most useful information available in SYNOPSIS and DESCRIPTION. When options grouped in [ ] without a |, one or more of them can be used. (-l, -w and -lw are valid.) 7/17/2009 rwjBROOKDALE COMMUNITY COLLEGE14

15. 7/17/2009 rwjBROOKDALE COMMUNITY COLLEGE15 Understanding a man Page The | signifies an OR condition. (e.g., Only one of -c, -m or -C can be used.) The... means that multiple occurrences of the preceding item are possible. ( wc can be used with multiple files.) EXIT STATUS indicates values returned on error.

16. Several simple commands Example: prt Syntax/Synopsis prt [ -c | -m | -C ] [ -lw ] [ file... ] Example: ed Syntax/Synopsis ed [ file... ] Example: ls Syntax/Synopsis ls [-OPTION] [fileName | substring] OPTION: -x= multi-column outut -F= prefix executables with *, directories with / and symbolic links with @ -a= shows all file names beginning with. Or.. -l= show long list -d= shows only dir names See pg 66 for complete options list. 7/17/2009 rwjBROOKDALE COMMUNITY COLLEGE16