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Shell: Quick Review

Shell: Quick Review. A Quick Review of the Basics. Some Basic Commands (1/2) Displaying the Data and Time: The date command The date command tells the system to print the date and time: Finding Out Who’s Logged In: The who Command

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Shell: Quick Review

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  1. Shell: Quick Review

  2. A Quick Review of the Basics • Some Basic Commands (1/2) • Displaying the Data and Time: The date command • The date command tells the system to print the date and time: • Finding Out Who’s Logged In: The who Command • The who command can be used to get information about all users who are currently logged into the system: $ date Sat Oct 29 15:40:52 EDT 1983 $ $ who pat tty29 Oct 29 14:40 ruth tty37 Oct 29 10:54 steve tty25 Oct 29 15:52 $

  3. A Quick Review of the Basics • Some Basic Commands (2/2) • Finding Out Who’s Logged In: The who Command • Echoing Characters: The echo Command • The echo command prints at the terminal whatever else you happen to type on the line $ who am i pat tty29 Oct 29 14:40 $ $ echo this is a test this is a test $ echo why not print out a longer line with echo? why not print out a longer line with echo? $ echo A blank line is displayed

  4. A Quick Review of the Basics • Working with Files (1/3) • The UNIX system recognizes only three basic types of files: • ordinary files • any file on the system that contains data, text, program instructions, or just about anything else • directory files • special files • A special file has a special meaning to the UNIX system, and its typically associated with some form of I/O

  5. A Quick Review of the Basics • Working with Files (2/3) • Listing Files: The ls Command • To see what files you have stored in your directory • Displaying the Contents of a File: The cat Command $ ls READ_ME names rje $ $ cat names Susan Jeff Henry Allan Ken $

  6. A Quick Review of the Basics • Working with Files (3/3) • Counting the Number of Words in a File: The wc Command • The number of lines contained in the file • The number of words contained in the file • The number of characters contained in the file $ wc names 5 5 27 names $

  7. A Quick Review of the Basics • Command Options • Most UNIX commands allow the specification of options at the time that a command is executed • Let’s generalize by saying that command options should precede file names on the command line $ wc –l names 5 names $ wc –c names 27 names $ wc –w names 5 names $

  8. A Quick Review of the Basics • Making a Copy of a File: The cp Command • In order to make a copy of a file, the cp command is used $ cp source_file destination_file $ cp names saved_names $

  9. A Quick Review of the Basics • Renaming a File: The mv Command • A file can be renamed with the mv command • The arguments to the mv command follow the same format as the cp command • When executing a mv or cp command, the UNIX system does not care whether the file specified as the second argument already exists $ mv saved_names hold_it $

  10. A Quick Review of the Basics • Removing a File: The rm Command • You can remove more than one file at a time with the rm command by simply specifying all such files on the command line $ rm wb collect mon $

  11. documents programs plan dact sys.A new.hire no.JSK AMG.reply wb collect mon A Quick Review of the Basics • Working with Directories (1/14) [Fig. 1] Example directory structure documents programs memos proposals letters wb collect mon plan dact sys.A new.hire no.JSK AMG.reply [Fig. 2] Directories containing subdirectories

  12. usr steve pat ruth documents programs wb collect mon plan dact sys.A new.hire no.JSK AMG.reply A Quick Review of the Basics • Working with Directories (2/14) • The Home Directory and Path Names • The UNIX system always associates each user of the system with a particular directory • When you log into the system, you are placed automatically into a directory called your home directory … memos proposals letters [Fig. 3] Hierarchical directory structure

  13. A Quick Review of the Basics • Working with Directories (3/14) • The Home Directory and Path Names • relative path names • absolute path names • The directory that is one level higher • The directory name . . • current directory • The directory name .

  14. A Quick Review of the Basics • Working with Directories (4/14) • Displaying Your Working Directory: The pwd Command • Changing Directories: The cd Command $ pwd /usr/steve $ $ ls documents programs $ cd documents $ pwd /usr/steve/documents $ cd .. $ pwd /usr/steve $

  15. usr steve pat ruth documents programs wb collect mon plan dact sys.A new.hire no.JSK AMG.reply A Quick Review of the Basics • Working with Directories (5/14) memos proposals letters [Fig. 4] Current Working directory is steve usr steve pat ruth documents programs memos proposals letters wb collect mon plan dact sys.A new.hire no.JSK AMG.reply [Fig. 5] cd documents

  16. A Quick Review of the Basics • Working with Directories (6/14) usr steve pat ruth documents programs memos proposals letters wb collect mon plan dact sys.A new.hire no.JSK AMG.reply [Fig. 6] cd .. usr steve pat ruth documents programs memos proposals letters wb collect mon plan dact sys.A new.hire no.JSK AMG.reply [Fig. 7] cd documents/letters

  17. A Quick Review of the Basics • Working with Directories (7/14) • More on the ls Command $ ls documents letters memos proposals $ ls documents/memos dact plan $ ls documents/memos/plan documents/memos/plan

  18. A Quick Review of the Basics • Working with Directories (8/14) • More on the ls Command $ ls -l total 2 drwxr-xr-x 5 steve DP3725 80 Jun 25 13:27 documents drwxr-xr-x 2 steve DP3725 96 Jun 25 13:31 programs $ $ ls –l programs total 4 -rwxr-xr-x 1 steve DP3725 358 Jun 25 13:31 collect -rwxr-xr-x 1 steve DP3725 1219 Jun 25 13:31 mon -rwxr-xr-x 1 steve DP3725 89 Jun 25 13:30 wb $

  19. A Quick Review of the Basics • Working with Directories (9/14) • Creating a Directory: The mkdir Command • To create a directory, the mkdir command must be used $ mkdir misc $ ls documents misc programs $ usr steve pat ruth misc documents programs memos proposals letters wb collect mon plan dact sys.A new.hire no.JSK AMG.reply [Fig. 8] Directory structure with newly created misc directory

  20. A Quick Review of the Basics • Working with Directories (10/14) • Copying a File from One Directory to Another • The cp command can be used to make a copy of a file from one directory into another $ cp programs/wb misc/wbx $ $ cp programs/wb misc/wb $ $ cp programs/wb misc $ $ cp wb collect mon ../misc $ $ pwd /usr/steve/misc $ cp ../program/collect . …

  21. A Quick Review of the Basics • Working with Directories (11/14) • Moving Files between Directories • The mv command can be used to rename a file $ cd documents $ $ mv memos/plan proposals/plan $ $ mv memos/plan proposals $ pwd /usr/steve/programs $ mv wb collect mon ../misc $ $ mv programs bin $

  22. A Quick Review of the Basics • Working with Directories (12/14) • Linking Files: The ln Command • The ln command provides an easy way for you to give more than one name to file ln from to $ cp wb writeback $ $ ln wb writeback $ $ ls -l total 5 -rwxr-xr-x 1 steve DP3725 358 Jun 25 13:31 collect -rwxr-xr-x 1 steve DP3725 1219 Jun 25 13:31 mon -rwxr-xr-x 2 steve DP3725 89 Jun 25 13:30 wb -rwxr-xr-x 2 steve DP3725 89 Jun 25 13:30 writeback $

  23. A Quick Review of the Basics • Working with Directories (13/14) • Linking Files: The ln Command • You can link a bunch of files at once into a directory using the format $ pwd /usr/pat/bin -rwxr-xr-x 1 pat DP3822 1358 Jan 15 11:01 lcat -rwxr-xr-x 2 pat DP3822 504 Apr 21 18:30 xtr $ ln /usr/steve/wb . $ ls -l -rwxr-xr-x 1 pat DP3822 1358 Jan 15 11:01 lcat -rwxr-xr-x 2 steve DP3725 89 Jun 25 13:30 wb -rwxr-xr-x 2 pat DP3822 504 Apr 21 18:30 xtr $ ln files directory

  24. A Quick Review of the Basics • Working with Directories (14/14) • Removing a Directory: The rmdir Command • You can remove a directory with the rmdir command $ rmdir /usr/steve/misc rmdir: /usr/steve/misc not empty $ $ rm –f dir

  25. A Quick Review of the Basics • File Name Substitution (1/2) • The Asterisk(*) • The shell automatically substitute the names of all of the files $ ls chapt1 chapt2 chapt3 chapt4 $ echo * chapt1 chapt2 chapt3 chapt4 $ $ ls a b c chapt1 chapt2 chapt3 chapt4 $ echo chapt* chapt1 chapt2 chapt3 chapt4 $ echo *t1 chapt1 $ echo *t* chapt1 chapt2 chapt3 chapt4 $ echo *x *x $

  26. A Quick Review of the Basics • File Name Substitution (2/2) • Matching Single Characters • The question mark (?) matches exactly one character • Square brackets ([ ]) • One character matching • [abc] matches one letter a, b or c • Range of characters matching • [0-9] matches the characters 0 through 9 • cf) [z-f] is not valid!!

  27. Standardoutput Standardinput Command A Quick Review of the Basics • Standard Input, Standard Output, and I/O Redirection (1/6) • Standard Input and Standard Output [Fig. 9] Typical UNIX command

  28. A Quick Review of the Basics • Standard Input, Standard Output, and I/O Redirection (2/6) • Standard Input and Standard Output • Example – sort command $ sort Tony Babara Harry Dick Ctrl + D Babara Dick Harry Tony $ Tony Babara Harry Dick Babara Dick Harry Tony sort [Fig. 10] sort command

  29. Standardoutput Standardinput Command file A Quick Review of the Basics • Standard Input, Standard Output, and I/O Redirection (3/6) • Output Redirection [Fig. 11] output redirection

  30. A Quick Review of the Basics • Standard Input, Standard Output, and I/O Redirection (4/6) • Output Redirection • Output redirection character : >, >> • > : redirect • >> : append • Examples $ who > users $ cat users oko tty01 sep 12 07:30 ai tty15 sep 12 13:32 ruth tty21 sep 12 10:10 pat tty24 sep 12 13:07 steve tty25 sep 12 13:03 $ $ cat file1 This is in file1. $ cat file2 This is in file2. $ cat file1 >> file2 $ cat file2 This is in file1. This is in file2.

  31. Standardinput Standardoutput Command file A Quick Review of the Basics • Standard Input, Standard Output, and I/O Redirection (5/6) • Input Redirection

  32. A Quick Review of the Basics • Standard Input, Standard Output, and I/O Redirection (6/6) • Input Redirection • Input of a command be redirected from a file • Input redirection character : < • Different output.. Why?? $ who > users $ wc –l users 5 users $ wc –l < users 5

  33. Output of Command 1 Input of Command 1 Input of Command 2 Output of Command 2 Command1 Command2 pipe A Quick Review of the Basics • Pipe (1/2)

  34. oko tty01 sep 12 07:30 ai tty15 sep 12 13:32 ruth tty21 sep 12 10:10 pat tty24 sep 12 13:07 steve tty25 sep 12 13:03 A Quick Review of the Basics • Pipe (2/2) • Example – who & wc $ who > users $ wc –l < users 5 $ who | wc –l 5 Output of who Input of wc -l Output of wc -l who wc -l pipe

  35. A Quick Review of the Basics • Standard Error • Most UNIX command write their error messages • Associated with terminal by default • Error redirection character : 2> $ ls x* x* not found $ ls x* > foo x* not found $ cat foo $ • How we can redirect the message?? $ ls x* 2> errors $ cat errors x* not found $

  36. A Quick Review of the Basics • More on Commands (1/2) • Typing More Than One Command on a Line • Separate each command with a semicolon (;) • Sending a Command to the Background • Using ampersand character (&) $ date; pwd Wed Arp 25 20:14:32 EST 2005 /usr/pat/bin $ $ sort data > out & Send the sort to the background 1258 Process id $ date your terminal is immediately available to do other work Thu Apr 26 13:45:09 EST 2005 $

  37. A Quick Review of the Basics • More on Commands (2/2) • The ps Command $ ps PID TTY TIME COMMAND 195 01 0:21 sh The shell 1353 01 0:00 ps This ps command 1258 01 0:10 sort The previous sort $ Process ID Terminal number Amount of computer time that process has used Name of process

  38. A Quick Review of the Basics • Command summary

  39. A Quick Review of the Basics • Command summary

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