bc는 유닉스/리눅스가 설치된 한경이면 어디든 있는 계산기 프로그램이다.
bc 사용 메뉴얼
$ man bc
NAME
bc - An arbitrary precision calculator language
SYNTAX
bc [ -hlwsqv ] [long-options] [ file ... ]
DESCRIPTION
bc is a language that supports arbitrary precision numbers with inter‐
active execution of statements. There are some similarities in the
syntax to the C programming language. A standard math library is
available by command line option. If requested, the math library is
defined before processing any files. bc starts by processing code from
all the files listed on the command line in the order listed. After
all files have been processed, bc reads from the standard input. All
code is executed as it is read. (If a file contains a command to halt
the processor, bc will never read from the standard input.)
This version of bc contains several extensions beyond traditional bc
implementations and the POSIX draft standard. Command line options can
cause these extensions to print a warning or to be rejected. This doc‐
ument describes the language accepted by this processor. Extensions
bc - 무한 정확도 계산기 언어
설명
bc 는 대화형으로 문장을 실행하는 무한 정확도의 숫자를 지원하는언어이며 약간 C 언어와 비슷한 문법을 가지고 있다. 명령행 옵션을 주면 표준 수
학 라이브러리를 사용할 수 있다. 옵션을 주면 화일들을 처리하기에 앞서 수학 라이브러리가 정의된다. bc 는 우선 명령에서 주어진 화일 순서대 로
처 리한다. 화일을 모두 처리한 후 bc 는 표준 입력을 읽는다. 모든 코드는 읽는 즉시 실행된다. ( 만약 화일 내의 코드에 처리를 중지하라는명령이
있다면 bc는 표준입력에서 읽지 않을 것이다. )
bc 현재 버전에서는 전통적인 bc 기능과 POSIX 표준 이외의확장 기능을 포함하고 있다. 명령행 옵션을 주면 확장 기능에 대한 경고 메세지를보여주 고
처리를 무시하게 할 수 있다. 이 문서에서는 GNU 버전의 처리기에서사용하는 언어를 설명한다. 확장 기능도 같이 설명한다.
옵션 -q (welcome 메세지 출력 방지)
옵션 -l (수학 함수 라이브러리 사용) 아래에서는 e(3/0/4) 즉 e^(3/4) 계산에 사용됨
옵션 -ql (-q와 -l을 합친 옵션)
quit; (실행 후 즉시 bc 종료하기)
아래는 이항분포 B(6, 1-e^(3/4)) 에서 확률 P(X>=4) 를 구하는 bc 스크립트 소스이다.
* 소스 파일명: test-01.bc
#!/usr/bin/bc -ql
# Execute: bc -l test-01.bc
define f(x) {
if (x <= 1)
return (1);
return (f(x - 1) * x);
}
define p() {
return 1.0 - e(-3.0/4.0);
}
define b(x) {
return (f(6)/f(x)/f(6-x))*(p()^x)*((1-p())^(6-x));
}
1 - (b(0) + b(1) + b(2) + b(3));
quit;
* 실행:
$ bc -ql test-01.bc
또는
$ cat test-01.bc | bc -ql
* 실행 결과:
.39688469988268586698
* 셀 스크립트로 bc를 실행하는 간단한 예제들
$ echo "1+2+3+4+5" | bc -l
15
$ echo "1+1/2+1/3+1/4+1/5" | bc -l
2.28333333333333333333
$ echo "1+1/2+1/3+1/4+1/5" | bc
1
$ echo "scale=5; 1+1/2+1/3+1/4+1/5" | bc
2.28333
$ cat for.txt
for (i=0; i<10; i++) {
print i; print "\n"
}
$ cat for.txt | bc -l
0
1
2
3
4
5
6
7
8
9
* 직각을 낀 두 변의 길이가 0.00000001 인 직각이등변삼각형의 빗변의 길이 구하기
$ echo "sqrt(0.1^8^2 + 0.1^8^2)" | bc -l
0
$ echo "sqrt(1^2 + 1^2)*0.1^8" | bc -l
.00000001414213562373
* 원주율 PI 값 계산하기
$ time echo "scale=10000; 4*a(1)" | bc -l
3.141592653589793238462643383279502884197169399375105820974944592307\
81640628620899862803482534211706798214808651328230664709384460955058\
22317253594081284811174502841027019385211055596446229489549303819644\
28810975665933446128475648233786783165271201909145648566923460348610\
45432664821339360726024914127372458700660631558817488152092096282925\
40917153643678925903600113305305488204665213841469519415116094330572\
70365759591953092186117381932611793105118548074462379962749567351885\
75272489122793818301194912983367336244065664308602139494639522473719\
07021798609437027705392171762931767523846748184676694051320005681271\
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37105079227968925892354201995611212902196086403441815981362977477130\
99605187072113499999983729780499510597317328160963185950244594553469\
08302642522308253344685035261931188171010003137838752886587533208381\
42061717766914730359825349042875546873115956286388235378759375195778\
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375676
real 2m52.269s
user 2m52.200s
sys 0m0.000s
[참고 사이트]
