Advanced UNIX. 2. The Shell (Ch.5, Sobell) Objectives. to supplement the Introduction to UNIX slides with extra information about the Shell

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1 Advanced UNIX CIS 218 Advanced UNIX 2. The Shell (Ch.5, Sobell) Objectives to supplement the Introduction to UNIX slides with extra information about the Shell CIS 218 Advanced UNIX 1

2 Overview 1. Redirection 2. Pipes 3. Background Jobs 4. Filename Generation CIS 218 Advanced UNIX 2

3 1. Redirection Command I/O is stream-based: command standard output standard input CIS 218 Advanced UNIX 3

4 $ cat This is a line of text. This is a line of text. Cat keeps copying lines of text Cat keeps copying lines of text until you press control-d at the until you press control-d at the beginning of a line. beginning of a line. $ You type a line; it is echoed control-d CIS 218 Advanced UNIX 4

5 Redirect Output Use > to redirect standard output to a file : standard output file command standard input CIS 218 Advanced UNIX 5

6 $ cat > sample.txt This text is being entered at the keyboard. Cat is copying it to a file. Press control-d to indicate the end of file. $ control-d $ cat file1.c file2.c file3.c > all-files.c CIS 218 Advanced UNIX 6

7 Redirect Input Use < to redirect standard input from a file : file standard input command standard output CIS 218 Advanced UNIX 7

8 $ cat < supply_orders 2000 sheets letterhead ordered: 10/7/97 1 box masking tape ordered: 10/8/97 $ $ cat supply_orders $ mail ad@ratree.psu.ac.th < letter.txt CIS 218 Advanced UNIX 8

9 Dangers Bad: $ cat orange pear > orange cat: input orange is output see noclobber in C Shell Good: $ cat orange pear > temp $ mv temp orange CIS 218 Advanced UNIX 9

10 Appending Output to a File Use >> to append: $ date > whoson $ cat whoson Fri May 29 09:24:19 GMT 2000 $ who >> whoson $ cat whoson Fri May 29 09:24:19 GMT 2000 jenny tty02 May 29 07:21 ad tty06 May 28 11:01 $ CIS 218 Advanced UNIX 10

11 2. Pipes Use a pipe to connect standard output of one command to standard input of another: command1 command2 standard input standard output CIS 218 Advanced UNIX 11

12 Use the operator between commands: $ command 1 command2 Same as: $ command1 > temp $ command2 < temp $ rm temp CIS 218 Advanced UNIX 12

13 $ ls more $ who grep ad ad tty06 May 23 10:31 $ who sort ad tty06 May 23 10:31 jenny tty02 May 21 15:29 scott tty03 May 23 09:02 Same as: $ who > temp $ sort < temp or $ sort temp CIS 218 Advanced UNIX 13

14 Filters A filter is a command that modifies its standard input, putting the changes onto its standard output: $ who sort lpr $ ps grep ad CIS 218 Advanced UNIX 14

15 The tee Command Passes its input through to standard output unchanged. Also saves input into a file: file command1 tee command2 standard input standard output CIS 218 Advanced UNIX 15

16 $ who tee who.out grep ad ad tty06 May 23 10:31 $ cat who.out jenny tty02 May 21 15:29 ad tty06 May 23 10:31 scott tty03 May 23 09:02 CIS 218 Advanced UNIX 16

17 3. Background Jobs A normal command executes in the foreground: you wait until it finishes before another command can be typed. Commands (jobs) can execute in the background. No need to wait for them before another command is typed. CIS 218 Advanced UNIX 17

18 Background jobs end with a & : $ gcc big-program.c & 1466 $ ls -l lpr & 1467 $ vi report.txt CIS 218 Advanced UNIX 18

PID TT STAT TIME COMMAND 1466 03 S 0:05 gcc big-program.

19 Killing a Background Job Cannot type control-c Use kill and the process ID (PID): $ kill 1466 Use ps to list PIDs: $ ps PID TT STAT TIME COMMAND S 0:05 gcc big-program.c S 0:04 ls -l lpr R 0:03 ps $ CIS 218 Advanced UNIX 19

20 4. Filename Generation Commands involving filenames (e.g. cat, ls) can include special characters in the filenames. called metacharacters three kinds:? * [...] CIS 218 Advanced UNIX 20

21 The? Special Character? matches any single character $ ls mem memo12 memo9 memoalex newmemo5 memo memo5 memoa memos $ ls memo? memo9 memo5 memoa memos $ lpr memo? continued CIS 218 Advanced UNIX 21

22 $ ls 7may4report may14report may4report.79 mayqreport may.report may4report may_report mayreport $ ls may?report mayqreport may.report may4report may_report CIS 218 Advanced UNIX 22

23 The * Special Character * matches any sequence of characters (0 or more characters) $ ls amemo memo memoa memosally user.memo mem memo.0612 memorandum sallymemo $ ls memo* memo memoa memosally memo.0612 memorandum continued CIS 218 Advanced UNIX 23

24 $ ls *.txt $ lpr *.txt $ ls *.c $ cat *.c > all-files $ more all-files $ rm *.c $ mv all-files all-files.c CIS 218 Advanced UNIX 24

25 The [...] Special Characters Match against any single character given inside [...] Can include - to give a range $ ls part1.txt part2.txt part3.txt part4.txt part5.txt $ lpr part[135].txt $ cat part[1-3].txt continued CIS 218 Advanced UNIX 25

26 Useful Ranges [a-z] [A-Z] any letter between a and z any letter between A and Z [0-9] any digit betwwn 0 and 9 Can combine: [a-z,0-9] continued CIS 218 Advanced UNIX 26

27 $ ls part0 part1 part2 part3 part4... part32 part33 part34 part35 $ ls part[0-9] $ ls part[12][0-9] $ ls part3[0-5] CIS 218 Advanced UNIX 27

28 Combining Special Characters $ ls [a-m]* $ ls *[x-z] $ lpr p*[0-9].c & CIS 218 Advanced UNIX 28

Introduction p. 1 Who Should Read This Book? p. 1 What You Need to Know Before Reading This Book p. 2 How This Book Is Organized p.

Introduction p. 1 Who Should Read This Book? p. 1 What You Need to Know Before Reading This Book p. 2 How This Book Is Organized p. 2 Conventions Used in This Book p. 2 Introduction to UNIX p. 5 An Overview