$ true && echo "Yes." Yes. $ false echo "Yes." Yes.

Transcription

1 SHELL programming

2 Shell 리스트 단순 list 구문 1 ; 구문 2 ; 구문 3 ;... AND list 구문 1 && 구문 2 && 구문 3 &&... OR list 구문 1 구문 2 구문 3... $ true && echo "Yes." Yes. $ false echo "Yes." Yes. Page 2

3 Shell 함수 함수 function_name () { } Page 3 statements [ue20@zeus ch2]$ vim function.sh #!/bin/sh yes_or_no(){ echo Is Your Name $1? while true do echo n Enter yes or no: read X case $X in y Y yes Yes YES) return 0;; n N no No NO) return 1;; *) echo Answer yes or no esac done } echo Original parameters are $* if yes_or_no $1 then echo Hi $1 else echo Oh! Sorry fi exit 0

4 Shell 에내장된명령 Shell script 내의 2 가지명령형태 명령프롬프트로부터실행가능한명령 Shell script 내에정의된내장명령 Page 4

5 Shell 에내장된명령 Break 반복문을빠져나올수있다. ch2]$ vim break.sh #!/bin/sh for var in do echo var is $var. if [ $var = 5 ] then break; fi done echo Break! exit 0 ~ [ue20@zeus ch2]$ Page 5

6 Shell 에내장된명령 : ( 콜론명령 ) 널명령, true 에대한별칭으로조건에대한논리지정 continue 반복문에서다음반복에서부터실행을계속한다. echo 문자열과줄바꿈문자를출력 eval 인자를실행 Page 6

7 Shell 에내장된명령 Exit n n 값의의미 exit 0 : 성공 exit 1 ~ 125 : 스크립트에서사용가능한에러코드. exit etc : 예약된코드. <ex> 126 : 파일이실행가능하지않았다. 127 : 명령이발견되지않았다. 128 이상 : Signal 발생 Page 7

8 Shell 에내장된명령 printf printf 형식문자열 매개변수 1 매개변수 2 printf 에서의 escape 문자. Escape Sequence \\ \a 경고 ( \b \f \n \r \t \v 설명역슬래시문자벨이나경고음을울린다 ) 백스페이스문자폼피드문자새줄문자개행문자탭문자수직탭문자 \ooo 8 진수값값 ooo 를값지는한문자 Page 8

9 Shell 에내장된명령 printf 의중요한변환지정자변환지정자설명 d 10 진수를출력한다. c 문자를출력한다. s 문자열 (string) 을출력한다. % % 문자를출력한다. Page 9

10 #/bin/bash y=1 while [ $y -le 12 ]; do x=1 while [ $x -le 12 ]; do printf "% 4d" $(( $x * $y )) let x++ done echo "" let y++ done Page 10

11 Shell 에내장된명령 return 함수반환 하나의숫자매개변수를가진다. set set 명령은쉘을위한파라미터변수를설정 Page 11

12 Shell 에내장된명령 Shift Shift 명령은모든파라미터변수를한단계아래로이동 ch2]$ vim shift.sh #!/bin/sh while [ $1!= ] do echo $1 shift done exit 0 Page 12

13 project (test_proj) cmake_minimum_required(version 2.6) set(src "main.c" "io.h" "read.c" "write.c" ) if(unix) add_custom_command( OUTPUT "${CMAKE_SOURCE_DIR}/TAGS" DEPENDS ${src} PRE_BUILD WORKING_DIRECTORY ${CMAKE_SOURCE_DIR} COMMAND etags ${src} ) endif() CMakeLists.txt 고급기술 : tag 자동생성 add_executable("test" ${src} "${CMAKE_SOURCE_DIR}/TAGS")

14 Makefile ( 내부적으로 cmake 이용 ) all: init_finished.txt if! test d../build_release ; then rm init_finished.txt; exit 1; fi cd../build_release;make no print directory debug: init_finished.txt if! test d../build_debug ; then rm init_finished.txt; exit 1; fi cd../build_debug;make no print directory VERBOSE=1 init_finished.txt:../src/cmakelists.txt mkdir p../build_release;cd../build_release;cmake G "Eclipse CDT4 Unix Makefiles"../src mkdir p../build_debug;cd../build_debug;cmake G "Eclipse CDT4 Unix Makefiles" D CMAKE_BUILD_TYPE=Debug../src touch init_finished.txt clean: rm rf../build_release rm rf../build_debug install_dependencies: sudo apt get install cmake exuberant ctags run_cgdb: make debug cgdb../build_debug/test

15 Bash version 3 Regular expressions

16 Regular Expressions grep and egrep

17 Previously Basic UNIX Commands Files: rm, cp, mv, ls, ln Processes: ps, kill Unix Filters cat, head, tail, tee, wc cut, paste find sort, uniq tr

18 Subtleties of commands Executing commands with find Specification of columns in cut Specification of columns in sort Methods of input Standard in File name arguments Special "-" filename Options for uniq

19 Today Regular Expressions Allow you to search for text in files grep command Stream manipulation: sed

20 Regular Expressions

21 What Is a Regular Expression? A regular expression (regex) describes a set of possible input strings. Regular expressions descend from a fundamental concept in Computer Science called finite automata theory Regular expressions are endemic to Unix vi, ed, sed, and emacs awk, tcl, perl and Python grep, egrep, fgrep compilers

22 Regular Expressions The simplest regular expressions are a string of literal characters to match. The string matches the regular expression if it contains the substring.

23 regular expression c k s UNIX Tools rocks. ma tch UNIX Tools sucks. ma tch UNIX Tools is okay. no match

24 Regular Expressions A regular expression can match a string in more than one place. regular expression a p p l e Scrapple from the apple. match 1 match 2

25 Regular Expressions The. regular expression can be used to match any character. regular expression o. For me to poop on. match 1 match 2

26 Character Classes Character classes [] can be used to match any specific set of characters. regular expression b [eor] a t beat a brat on a boat match 1 match 2 match 3

27 Negated Character Classes Character classes can be negated with the [^] syntax. regular expression b [^eo] a t beat a brat on a boat match

28 More About Character Classes [aeiou] will match any of the characters a, e, i, o, or u [kk]orn will match korn or Korn Ranges can also be specified in character classes [1-9] is the same as [ ] [abcde] is equivalent to [a-e] You can also combine multiple ranges [abcde ] is equivalent to [a-e1-9] Note that the - character has a special meaning in a character class but only if it is used within a range, [-123] would match the characters -, 1, 2, or 3

29 Named Character Classes Commonly used character classes can be referred to by name (alpha, lower, upper, alnum, digit, punct, cntrl) Syntax [:name:] [a-za-z] [[:alpha:]] [a-za-z0-9] [[:alnum:]] [45a-z] [45[:lower:]] Important for portability across languages

30 Anchors Anchors are used to match at the beginning or end of a line (or both). ^ means beginning of the line $ means end of the line

31 regular expression ^ b [eor] a t beat a brat on a boat ma tch regular expression b [eor] a t $ beat a brat on a boat ma tch ^word$ ^$

32 Repetition The * is used to define zero or more occurrences of the single regular expression preceding it.

33 regular expression y a * y I got mail, yaaaaaaaaaay! ma tch regular expression o a * o For me to poop on. ma tch.*

34 Match length A match will be the longest string that satisfies the regular expression. regular expression a. * e Scrapple from the apple. n o n o y e s

35 Repetition Ranges Ranges can also be specified { } notation can specify a range of repetitions for the immediately preceding regex {n} means exactly n occurrences {n,} means at least n occurrences {n,m} means at least n occurrences but no more than m occurrences Example:.{0,} same as.* a{2,} same as aaa*

36 Subexpressions If you want to group part of an expression so that * or { } applies to more than just the previous character, use ( ) notation Subexpresssions are treated like a single character a* matches 0 or more occurrences of a abc* matches ab, abc, abcc, abccc, (abc)* matches abc, abcabc, abcabcabc, (abc){2,3} matches abcabc or abcabcabc

37 grep grep comes from the ed (Unix text editor) search command global regular expression print or g/re/p This was such a useful command that it was written as a standalone utility There are two other variants, egrep and fgrep that comprise the grep family grep is the answer to the moments where you know you want the file that contains a specific phrase but you can t remember its name

38 Family Differences grep - uses regular expressions for pattern matching fgrep - file grep, does not use regular expressions, only matches fixed strings but can get search strings from a file egrep - extended grep, uses a more powerful set of regular expressions but does not support backreferencing, generally the fastest member of the grep family agrep approximate grep; not standard

39 Syntax Regular expression concepts we have seen so far are common to grep and egrep. grep and egrep have slightly different syntax grep: BREs egrep: EREs (enhanced features we will discuss) Major syntax differences: grep: \( and \), \{ and \} egrep: ( and ), { and }

40 Protecting Regex Metacharacters Since many of the special characters used in regexs also have special meaning to the shell, it s a good idea to get in the habit of single quoting your regexs This will protect any special characters from being operated on by the shell If you habitually do it, you won t have to worry about when it is necessary

41 Escaping Special Characters Even though we are single quoting our regexs so the shell won t interpret the special characters, some characters are special to grep (eg * and.) To get literal characters, we escape the character with a \ (backslash) Suppose we want to search for the character sequence a*b* Unless we do something special, this will match zero or more a s followed by zero or more b s, not what we want a\*b\* will fix this - now the asterisks are treated as regular characters

42 Egrep: Alternation Regex also provides an alternation character for matching one or another subexpression (T Fl)an will match Tan or Flan ^(From Subject): will match the From and Subject lines of a typical message It matches a beginning of line followed by either the characters From or Subject followed by a : Subexpressions are used to limit the scope of the alternation At(ten nine)tion then matches Attention or Atninetion, not Atten or ninetion as would happen without the parenthesis - Atten ninetion

43 Egrep: Repetition Shorthands The * (star) has already been seen to specify zero or more occurrences of the immediately preceding character + (plus) means one or more abc+d will match abcd, abccd, or abccccccd but will not match abd Equivalent to {1,}

44 Egrep: Repetition Shorthands cont The? (question mark) specifies an optional character, the single character that immediately precedes it July? will match Jul or July Equivalent to {0,1} Also equivalent to (Jul July) The *,?, and + are known as quantifiers because they specify the quantity of a match Quantifiers can also be used with subexpressions (a*c)+ will match c, ac, aac or aacaacac but will not match a or a blank line

45 Grep: Backreferences Sometimes it is handy to be able to refer to a match that was made earlier in a regex This is done using backreferences \n is the backreference specifier, where n is a number Looks for nth subexpression For example, to find if the first word of a line is the same as the last: ^\([[:alpha:]]\{1,\}\).* \1$ The \([[:alpha:]]\{1,\}\) matches 1 or more letters

46 Practical Regex Examples Variable names in C [a-za-z_][a-za-z_0-9]* Dollar amount with optional cents \$[0-9]+(\.[0-9][0-9])? Time of day (1[012] [1-9]):[0-5][0-9] (am pm) HTML headers <h1> <H1> <h2> <[hh][1-4]>

47 grep Family Syntax grep [-hilnv] [-e expression] [filename] egrep [-hilnv] [-e expression] [-f filename] [expression] [filename] fgrep [-hilnxv] [-e string] [-f filename] [string] [filename] -h Do not display filenames -i Ignore case -l List only filenames containing matching lines -n Precede each matching line with its line number -v Negate matches -x Match whole line only (fgrep only) -e expression Specify expression as option -f filename Take the regular expression (egrep) or a list of strings (fgrep) from filename

48 grep Examples grep 'men' GrepMe grep 'fo*' GrepMe egrep 'fo+' GrepMe egrep -n '[Tt]he' GrepMe fgrep 'The' GrepMe egrep 'NC+[0-9]*A?' GrepMe fgrep -f expfile GrepMe Find all lines with signed numbers $ egrep [-+][0-9]+\.?[0-9]* *.c bsearch. c: return -1; compile. c: strchr("+1-2*3", t-> op)[1] - 0, dst, convert. c: Print integers in a given base 2-16 (default 10) convert. c: sscanf( argv[ i+1], "% d", &base); strcmp. c: return -1; strcmp. c: return +1; egrep has its limits: For example, it cannot match all lines that contain a number divisible by 7.

49 Fun with the Dictionary /usr/dict/words contains about 25,000 words egrep hh /usr/dict/words beachhead highhanded withheld withhold egrep as a simple spelling checker: Specify plausible alternatives you know egrep "n(ie ei)ther" /usr/dict/words neither How many words have 3 a s one letter apart? egrep a.a.a /usr/dict/words wc l 54 egrep u.u.u /usr/dict/words cumulus

50 Other Notes Use /dev/null as an extra file name Will print the name of the file that matched grep test bigfile This is a test. grep test /dev/null bigfile bigfile:this is a test. Return code of grep is useful grep fred filename > /dev/null && rm filename

51 This is one line of text x xyz \m ^ $. [xy^$x] [^xy^$z] [a-z] r* r1r2 \(r\) \n \{n,m\} r+ r? r1 r2 (r1 r2)r3 (r1 r2)* {n,m} o.*o Ordinary characters match themselves (NEWLINES and metacharacters excluded) Ordinary strings match themselves Matches literal character m Start of line End of line Any single character Any of x, y, ^, $, or z Any one character other than x, y, ^, $, or z Any single character in given range zero or more occurrences of regex r Matches r1 followed by r2 Tagged regular expression, matches r Set to what matched the nth tagged expression (n = 1-9) Repetition One or more occurrences of r Zero or one occurrences of r Either r1 or r2 Either r1r3 or r2r3 Zero or more occurrences of r1 r2, e.g., r1, r1r1, r2r1, r1r1r2r1, ) Repetition input line regular expression fgrep, grep, egrep grep, egrep grep egrep Quick Reference

52 실습 다음작업을하는 shell program 을작성한다. 1. 파일내용채우기 1000.txt 파일에 a 를 1000 번씀. Page 52

53 Reference KLDP Shell Programming 의기본 초보자용 Shell Programming Page 53