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Computer Programming Batch & Shell Programming 9 th Lecture

Computer Programming Batch & Shell Programming 9 th Lecture. 김현철 컴퓨터공학부 서울대학교 2009 년 가을학기. Slide Credits. 엄현상 교수님 서울대학교 컴퓨터공학부 Computer Programming, 2007 봄학기. 순서. Bash Shell Programming Quoting 보충 Looping Per-Case Execution Array Example Miscellaneous Q&A.

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Computer Programming Batch & Shell Programming 9 th Lecture

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  1. Computer ProgrammingBatch & Shell Programming 9th Lecture 김현철 컴퓨터공학부 서울대학교 2009년 가을학기

  2. Slide Credits • 엄현상 교수님 • 서울대학교 컴퓨터공학부 • Computer Programming, 2007 봄학기

  3. 순서 • Bash Shell Programming • Quoting 보충 • Looping • Per-Case Execution • Array • Example • Miscellaneous • Q&A

  4. Bourne Shell Scripts #!/bin/sh # Generate some info date echo $HOME echo $USER echo $PATH cal • Result 2007. 04. 03. (화) 11:52:37 KST /csehome/net001 net001 /usr/local/bin:/usr/bin:/bin … (omitted)

  5. Variables and Backquotes cname="Computer Programming Class" gsnum=70 echo $cname: “#” of good students = $gsnum Stored as a String Computer Programming Class: # of good students = 70 … (same as above) bsnum=10 stnum=$gsnum+$bsnum echo $cname: total "#" of students = $stnum Stored as a String Computer Programming Class: total # of students = 70+10 … (same as above except for the last two lines) stnum=`expr $gsnum`+ $bsnum` echo $cname: total "#" of students = $stnum Computer Programming Class: total # of students = 80

  6. Quoting : Rules 1) Single Quotes(')따옴표로 둘러 쌓여 기술된 모든 특수문자들은 쉘로부터의 번역이모두 금지된다. 따옴표는 특수문자의 기능을 필요에 의해 제한하기위해서 사용한다. 2) Double Quotes(“)쌍 따옴표는 따옴표와 동일한 기능을 수행한다. 단, $, `, \의 3가지특수문자는 영향을 받지않고 정상대로 쉘에의해 번역된다. 3) Backquotes (`)역 따옴표에 기술되어 있는 문자열을 쉘에게 실행 명령어라는 것을알려주기 위해 사용한다. 쉘은 이 명령어를 실행한후 생성된 출력을명령어가 지정된 위치에 위치시킨다.( 주의 ) 이상 3가지의 보호문자는 반드시 쌍으로 이루어 진다.만일 쌍으로 지정되지 않은 경우에는 문법 에러를 발생한다. 4) Backslash(\)역 슬래쉬는 연이어 기술된 다음 한자가 갖고 있는 특수문자의처리를 쉘이 수행하지 못하도록 처리한다.

  7. Quoting • Examples of Quoting Rules person=hatter

  8. Command-Line Arguments echo '1st command-line argument = $1' echo "2nd command-line argument = $2" echo 3rd argument = $3 echo "# of arguments = $#" echo Entire list of arguments = $* • Result martini:~$ arg.sh 1 2 3 1st command-line argument = $1 2nd command-line argument = 2 3rd argument = 3 # of arguments = 3 Entire list of arguments = 1 2 3

  9. 테스트 연산자

  10. Conditional Execution Space if [ $1 –lt $2 ]; then echo $1 is less than $2 elif [ $1 –gt $2 ]; then echo $1 is greater than $2 else echo $1 equals to $2 fi Space • Result martini:~$ cond.sh 1 2 1 is less than 2 martini:~$ cond.sh 2 1 2 is greater than 1 martini:~$ cond.sh 1 1 1 equals to 1

  11. Bourne Shell Script Example if [ -z $1 ] || [ -z $2 ]; then echo usage: $0 source_dir target_dir else SRC_DIR=$1 DST_DIR=$2 OF=output.`date +%y%m%d`.tar.gz if [ -d $DST_DIR ]; then tar -cvzf $DST_DIR/$OF $SRC_DIR else mkdir $DST_DIR tar -cvzf $DST_DIR/$OF $SRC_DIR fi fi • Execution martini:~$backup.sh srcdir dstdir

  12. Quoting 보충 • Examples of Quoting Rules person=hatter

  13. Shell 특수변수 • ┌────┰─────────────────────────────┐│ 변수   ┃ 목적                                                      │├────╂─────────────────────────────┤│ $0     ┃명령어 라인상의 명령어 이름이 설정                        │├────╂─────────────────────────────┤│ $#      ┃명령어 라인상에 기술되어 있는 인자의 갯수가 설정           │├────╂─────────────────────────────┤│ $*     ┃명령어 라인내의 전체 인자가 설정                           │├────╂─────────────────────────────┤│ "$@"    ┃$*와 같다. 그러나따옴표로 둘러쌓인 인자를 하나의 인자로   ││         ┃처리하는 것이 $*와 틀린 점이다.                            │├────╂─────────────────────────────┤│ $$      ┃현재의 프로세스 식별자(PID)가 설정                        │├────╂─────────────────────────────┤│ $!      ┃Background에서 직전에 실행됐던 프로세스의 식별자가 설정   │├────╂─────────────────────────────┤│ $?      ┃직전에 Foreground에서 실행됐던 명령어의 종료상태가설정    │├────╂─────────────────────────────┤│ $-      ┃현재 설정된 쉘 옵션이 설정                                 │

  14. Looping Double Quotes around $@ for arg in "$@"; do # correct echo $arg done for arg in "$*"; do # wrong echo $arg done • Result martini:~$ loop.sh 1 "2 2" 3 1 2 2 3 1 2 2 3

  15. Looping (계속) martini:~$ ls backup.C backup.c backup1.C backup1.c martini:~$ more for.sh for cfilename in *$1*u?.[cC]; do echo $cfilename done • Results martini:~$ for.sh a backup.C backup.c martini:~$ for.sh c backup.C backup.c

  16. Looping (계속) let i=i+1 # bash only i=0 while [ $i –lt 3 ]; do echo $i i=`expr $i + 1` done` • Result martini:~$ while.sh 0 1 2

  17. Per-Case Execution echo Enter your command ＼(who, list, or quit ＼) while read command; do case $command in who) who; echo Done with running who;; list) ls; echo Done with running ls;; quit) break;; *) echo Enter who, list, or quit;; esac done • Result martini:~$ case.sh Enter your command (who, list, or quit) who net001 pts/2 Mar 31 13:26 … (omitted) Done with running who list … Done with running ls date Enter who, list, or quit quit martini:~$

  18. Array (bash Only) • Variable Containing Multiple Values • No Maximum Limit to the Size • No Requirements That Member Variables Be Indexed or Assigned Contiguously • Zero-Based

  19. Array (계속) a1=(one two three) echo ${a1[*]} echo a1[*] echo ${a1[@]} echo a1[@] echo ${a1[0]} echo a1[0] echo ${a1[3]} unset a1[3] unset a1[*] echo ${a1[0]} # unset i=0 echo $i unset i echo $i ------- 0 • Result one two three a1[*] one two three a1[@] one a1[0]

  20. Bash Script Example (계속) i=0 status=0 if [ $# -lt 1 ]; then echo Usage: $0 [-b base1 base2...] [-c expo1 expo2...] exit 1 fi for arg in "$@"; do if [ -n "`echo $arg | grep '-'`" ]; then if [ $arg = -b ]; then status=1 elif [ $arg = -c ]; then status=2 fi else case $status in 1 ) base[$i]=$arg; i=`expr $i + 1` ;; 2 ) exponent[$i]=$arg; i=`expr $i + 1` ;; * ) echo Usage: $0 [-b base1 base2...] [-c expo1 expo2...]; exit 1 ;; esac fi done # to be continued on the next slide

  21. Bash Script Example (계속) if ! [ -d OUTPUT ]; then mkdir OUTPUT if [ $? -gt 0 ]; then # if the exit status of the previous command indicates a failure echo Remove/Rename the OUTPUT File exit 1 fi fi for i in ${base[@]}; do for j in ${exponent[@]}; do if ! [ -e ./OUTPUT/output.$i.$j ]; then ./pow $i $j >> ./OUTPUT/output.$i.$j fi done done • Execution martini:~$powsim.sh –b 3 4 5 –c 12 14 16

  22. Shell Programming 보충 • Bash Variable Naming • letter -> A | B | … | Z | a | b | … | z • digit -> 0 | 1 | … | 9 • u_s -> _ • var_name -> (letter | u_s)(letter | digit | u_s)* a=1 echo $aa To show the value 1, this ‘a’ should be ~, !, @, #, %, ^, *, -, +, =, {, [, }, ], :, ＼,, ., ?, /, or [space] • Result martini:~$ var_naming.sh

  23. Shell Programming 보충 (계속) • Character Echoing • Shown as Expected If There Is Space Before and After the Character (Refer to Handout 7) • Possibly Shown Verbatim If There Is an Adjacent Character e.g., ~~ a=1 echo $aa --- To show the value 1, the latter ‘a’ should be ~, !, @, #, %, ^, *, -, +, =, {, [, }, ], :, ＼,, ., ?, /, or [space] martini:~$ echo ~# ~# • Some Exceptions

  24. Miscellaneous • Stream Editor: sed • Global Search and Replace • Character Translator: tr • Regular Expressions • for Editors (Including sed) and grep • Option Interpretation: getopts • Functions • Signals • …

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