请问关于bc命令的解释

yuandeshen

scale=5000; a(1)*4 | bc -l

请问这个，怎么解释，谢谢。

wenhq

语法错误啊。。。。
NAME
       bc - An arbitrary precision calculator language

SYNTAX
       bc [ -hlwsqv ] [long-options] [  file ... ]

VERSION
       This man page documents GNU bc version 1.06.

DESCRIPTION
       bc is a language that supports arbitrary precision numbers with interactive 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 document describes the language accepted by this processor.  Extensions will
       be identified as such.

yuandeshen

回复 2# wenhq
不会吧，这个脚本能运行啊


    CONCURRENCY=64
TIME_START=`date`
for ((idx = 0; idx < $CONCURRENCY; idx++))
do
    time echo "scale=5000; a(1)*4" | bc -l > /dev/null &
done

echo    "$TIME_START Start"

yuandeshen

回复 4# Hongqiyaodao

不好意思，a(1)*4，反切弧，实在愚钝，不明白
   

Shell_HAT

回复 3# yuandeshen


这里用的就是反三角函数atan()，在bc中是用a()来表示。atan(1)*4就是圆周率嘛

yuandeshen

回复 6# Shell_HAT


    谢谢，明白了，就是pi，如果scale=1024，就是super pi软件跑1M的意思对不？