[请教]在fortran中读取ASCII码数据文件时...

abcdefg100

在fortran中读取ASCII码数据文件时,如何让程序从文件的指定行开始读?

snower222

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心灯

原帖由 abcdefg100 于 2006-9-20 09:43 发表
在fortran中读取ASCII码数据文件时,如何让程序从文件的指定行开始读?

遇到同样问题，不知道该如何实现？

每行的字符数不一样多，不知道如何实现从行首读到行尾？（预先定义字符长度为定值的方法除外，这种方法先暂时用着，应付着...）

能不能让程序自动判断每行的行尾所在的列数，然后返回一个数值，之后才定义字符变量的长度，读入数组？貌似难度大了一些..... ：D

心灯

（建议版主把这个帖子移动到编程版fortran专题下）

下面的方法虽然解决不了我的问题，不过也是很有价值的。

From:    http://www.tek-tips.com/viewthread.cfm?qid=1315394&page=1

How to read data from specific line in a file  


sougandh (TechnicalUser)         
21 Dec 06 12:11
Hi,
    Here is my problem. My file is in the following format.
    It has 5 columns with first two being integers and 3-5 are  floating values.

   file format (similar format with different values)

      col 1     col 2       col 3    col 4     col 5

     5001       1001        12.34   11.34    43.454
     5001       1002        11.54   65.43    65.234
     5001       1003        12.54   54.64    65.778
     .          .           .       .        .
     .          .           .       .        .
     5001       1099        14.65   16.53    12.568
     5001       1100        13.65   13.54    12.545     
     5002       1001        12.34   11.34    43.454
     5002       1002        11.54   65.43    65.234
     5002       1003        12.54   54.64    65.778
     .          .           .       .        .
     .          .           .       .        .
     5002       1099        13.45   51.15    61.542
     5002       1100        13.65   13.54    12.545
     
     so on...

     That means, for each number in column 1 i have 100 values. Or i should say the column 1 number doesnt change for for 100 rows and then it increases. Infact  my original file has (5760 x 4633) rows.

    Now here is how i need to read it:

There is a variable 'crhr' which returns a value which corresponds to any of the values in column 1. For example it may be 5002 or 5050 or anything. So when this variable has a value of 5002 what i need is i should be able to read the rows corresponding to the number 5002 and store it in an array.

  My problem now is how do i make Fortran start reading the file from a particular line based on the value returned by the variable 'crhr'


thanks
sougandh

-----------------------------------------------------
Helpful Member!xwb (Programmer)         
21 Dec 06 16:30
Are all the lines the same size (in characters).  If so, then you can use formatted reads on direct access files
CODE
program main
   integer FHAND, TMAX, RMAX
   parameter (TMAX=10, RMAX=5, FHAND=88)
   real t(TMAX)
   integer reqd(RMAX)
   data reqd/ 1, 2, 16, 8, 4 /
      
   ! file - the data file
   ! status - always old
   ! form - formatted for human readable data
   !      - unformatted for binary data
   ! access - always direct.  The alternative is sequential
   ! recl - number of characters incl LF
   open (FHAND, &
      file='data.txt', &
      status='old', &
      form='FORMATTED', &
      access='direct', &
      recl=51)
   do i = 1, RMAX
      ! Read record reqd(i)
      read (FHAND, '(10F5.1)', rec=reqd(i)) (t(j), j = 1, TMAX)
      write (*, '(10F5.1)') (t(j), j = 1, TMAX)
   enddo
   close (FHAND)
   stop
end program