如何从FORTRAN中的字符串读取数字数据 [英] How to read numeric data from a string in FORTRAN

问题描述

我在FORTRAN中有一个字符串数组，结果如下：CI-能量--- th = 89 ph = 120'。如何从字符串中提取字符'120'并存储到实变量中？

字符串写入文件'input.DAT'。我已经写了FORTRAN代码：

$ p code $ implicit real * 8（ah，oz）
character（39）line
open（1，file ='input.DAT'，status ='old'）
read（1，'（A）'）line，phi
write（*，'（A ）'）line
write（*，*）phi
end

执行它显示：

pre $ 在文件string.f的第5行（单元= 1，file ='input.dat'）
Fortran运行时错误：文件结尾


我给出了'39'作为字符数组，因为有39个字符，包括字符串中的'spaces'到'120'。

解决方案

假设真实数字想要读取出现在字符串中最后一个等号后面，可以使用SCAN内部函数来查找该位置，然后从该字符串的其余部分读取数字，如以下程序中所示。

 程序xreadnum 
隐式无
整数:: ipos 
 integer，parameter :: nlen = 100 
 character（len = nlen）:: str 
 real :: xx 
 str =结果：CI- Energies --- th = 89 ph = 120
 ipos = scan（str，=，back = .true。）
 print *，从真正的变量读取'// trim（str（1 + ipos :) ）//'
 read（str（1 + ipos：），*）xx 
 print *，xx =，xx 
结束程序xreadnum 
！ gfortran输出：
！从'120'
阅读真实变量！ xx = 120.000000 
  

I have a character string array in FORTRAN as ' results: CI- Energies --- th= 89 ph=120'. How do I extract the characters '120' from the string and store into a real variable?

The string is written in the file 'input.DAT'. I have written the FORTRAN code as:

implicit real*8(a-h,o-z)
character(39)  line
open(1,file='input.DAT',status='old')
read(1,'(A)') line,phi
write(*,'(A)') line
write(*,*)phi
end

Upon execution it shows:

At line 5 of file string.f (unit = 1, file = 'input.dat')
Fortran runtime error: End of file

I have given '39' as the dimension of the character array as there are 39 characters including 'spaces' in the string upto '120'.

解决方案

Assuming that the real number you want to read appears after the last equal sign in the string, you can use the SCAN intrinsic function to find that location and then READ the number from the rest of the string, as shown in the following program.

program xreadnum
implicit none
integer :: ipos
integer, parameter :: nlen = 100
character (len=nlen) :: str
real :: xx
str  = "results: CI- Energies --- th= 89 ph=120"
ipos = scan(str,"=",back=.true.)
print*,"reading real variable from '" // trim(str(1+ipos:)) // "'"
read (str(1+ipos:),*) xx
print*,"xx = ",xx
end program xreadnum
! gfortran output:
! reading real variable from '120'
! xx =    120.000000    

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