c - 如何使用 C 从 .txt 文件中读取最后 3 个变量值

Question

我的 C 语言编程经验有限，但由于软件限制，我不得不使用这种语言。我正在尝试为 CFD 软件编写用户自定义。

软件在计算过程中写入一个输出文件，我想监控变量“PERCENT FILLED”，当数值稳定时终止模拟。我可以终止代码，我遇到的问题是使用 C 读取 PERCENT FILLED 的值，我可以在 python 或 shell 脚本中轻松执行此操作，但我真的很难使用 C。

可能有更优雅的方法来实现这一点，我很乐意学习，但我不是经验丰富的程序员，所以我可能会迷失在复杂的解决方案中。

我试图通过将任务分解成更小的子任务来做到这一点。代码的效率并不重要，因为这个函数不必经常运行并且要读取的文件不是很大。我相信有更快更优雅的方法可以做到这一点!使用网络上的其他代码并修改它们，我想出了以下内容。

我尝试完成以下子任务:A)删除所有包含“PERCENT FILLED”的行并将它们写入文件(PERCENT FILLED.txt)B) 读取此文件中的行数，然后将最后 3 行读取到单独的变量中。C) 然后我需要重新格式化这些变量。例如，将 3 个变量从“PERCENT FILLED = 6.72902E+00”形式的字符串更改为浮点值，例如 6.72902。

我已经完成了 A)，B) 有错误，并且不知道从哪里开始 C)。

B) 中的错误 - 当我运行代码时，它在 while 循环中正确地为 line1、line2 和 line3 分配了值，但是一旦在 while 循环之外，所有值都会更改为 line1 的值。这个我不明白。任何人都可以帮助我理解和解决这个问题吗？

示例代码输出:

line3: PERCENT FILLED =   6.31275E+00
line2: PERCENT FILLED =   6.50146E+00
line1: PERCENT FILLED =   6.72902E+00
****************** 
out line1: PERCENT FILLED =   6.72902E+00
out line2: PERCENT FILLED =   6.72902E+00
out line3: PERCENT FILLED =   6.72902E+00

C) 部分 - 我不知道从哪里开始。看起来有足够的内联信息可以使用 atof() 将字符串转换为 float 。但是，我首先需要从字符串的开头删除 PERCENT FILLED =，然后转换工程编号格式(某些值为 1.00E+02，因此简单地删除最后 4 个字符 - E+00 - 将不起作用)。我不知道该怎么做。任何帮助，将不胜感激。

示例输入文件(通过删除 PERCENT FILLED 值之间的可能行简化):

  Step = 171 Iteration = 0 Time step = 0.014849 Time = 4.834002
  Iter Variable Solver Loops          Delta      Solve CPU       Form CPU
     0        F  EXPLC     4   1.0000000E+00       0.007999       0.000000
 FRACTION SOLID = 0.000000e+00 %
 PERCENT FILLED =   5.46882E+00
  Step = 172 Iteration = 0 Time step = 0.029698 Time = 4.863700
  Iter Variable Solver Loops          Delta      Solve CPU       Form CPU
     0        F  EXPLC    11   1.0000000E+00       0.018997       0.000000
 FRACTION SOLID = 0.000000e+00 %
 PERCENT FILLED =   5.70902E+00
  Step = 173 Iteration = 0 Time step = 0.029698 Time = 4.893398
  Time step reduced by COURANT limit in free_surface, c_lim = 2.032750e-02
  Iter Variable Solver Loops          Delta      Solve CPU       Form CPU
     0        F  EXPLC     6   1.0000000E+00       0.010998       0.000000
 FRACTION SOLID = 0.000000e+00 %
 PERCENT FILLED =   5.89665E+00
  Step = 174 Iteration = 0 Time step = 0.020328 Time = 4.904356
  Iter Variable Solver Loops          Delta      Solve CPU       Form CPU
     0        F  EXPLC     7   1.0000000E+00       0.011997       0.000000
 FRACTION SOLID = 0.000000e+00 %
 PERCENT FILLED =   6.08026E+00
  Step = 175 Iteration = 0 Time step = 0.040655 Time = 4.945011
  Time step reduced by COURANT limit in free_surface, c_lim = 2.547617e-02
  Iter Variable Solver Loops          Delta      Solve CPU       Form CPU
     0        F  EXPLC     9   1.0000000E+00       0.016998       0.000000
 FRACTION SOLID = 0.000000e+00 %
 PERCENT FILLED =   6.31275E+00
  Step = 176 Iteration = 0 Time step = 0.025476 Time = 4.955307
  Time step reduced by COURANT limit in free_surface, c_lim = 1.997734e-02
  Iter Variable Solver Loops          Delta      Solve CPU       Form CPU
     0        F  EXPLC     9   1.0000000E+00       0.016994       0.000000
 FRACTION SOLID = 0.000000e+00 %
 PERCENT FILLED =   6.50146E+00
  Step = 177 Iteration = 0 Time step = 0.039955 Time = 4.989764
  Time step reduced by COURANT limit in free_surface, c_lim = 2.547537e-02
  Iter Variable Solver Loops          Delta      Solve CPU       Form CPU
     0        F  EXPLC    13   1.0000000E+00       0.024994       0.000000
 FRACTION SOLID = 0.000000e+00 %
 PERCENT FILLED =   6.72902E+00

我当前的代码:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main()
{
    char line[1000];
    char *pch;
    char c[] = "PERCENT FILLED =";
    char buff[1000];


/* Create a list of PERCENT FILLED values and write to file - copy every line containing PERCENT FILLED from p.out file*/
    FILE *fp = fopen("inputFILE.txt", "r");
    FILE *op = fopen("PERCENT_FILLED.txt", "w");

    if(fp == NULL || op == NULL)
       {
          fprintf(stderr, "Error opening file.");
          exit(1);
       }
    else 
       {
         while (fgets(line, sizeof(line), fp) != 0)
           {
              if((pch = strstr (line, c))!= 0)
              fprintf(op, "%s", line);
           }
       }

   fclose(fp);
   fclose(op);


/* Get the total number of lines in the file PERCENT_FILLED.txt   */

   FILE* myfile = fopen("PERCENT_FILLED.txt", "r");
   int ch, number_of_lines = 0;
   int line_num = 0;
   int count = 0;
   char readline[256];                                /* or other suitable maximum line size */
   char* line1;
   char* line2;
   char* line3;

    do 
    {
        ch = fgetc(myfile);
        if(ch == '\n')
            number_of_lines++;
    } while (ch != EOF);

    // last line doesn't end with a new line!
    // but there has to be a line at least before the last line
    if(ch != '\n' && number_of_lines != 0) 
        number_of_lines++;

    fclose(myfile);




/* Get the last 3 PERCENT_FILLED values from the PERCENT_FILLED.txt   */


    FILE* infile = fopen("PERCENT_FILLED.txt", "r");

    if ( infile != NULL )
    {   
        while (fgets(readline, sizeof line, infile) != NULL) /* read a line */
        {   
            if (count == (number_of_lines-4))
            {   
               line3 = readline;
               count++;
               printf("\nline3:%s", line3);
            }   
            else if (count == (number_of_lines-3))
            {  
               line2 = readline;
               count++;
               printf("line2:%s", line2);
            }
            else if (count == (number_of_lines-2))
            {
               line1 = readline;
               count++;
               printf("line1:%s", line1);
            }
            else
            {   
                count++;
                printf("readline:%s count:%d\n", readline, count);
            }   
        }   
        fclose(infile);
    }   
    printf("******************\n");
    printf("out line1:%s", line1);
    printf("out line2:%s", line2);
    printf("out line3:%s\n\n", line3);


/* strip "PERCENT FILLED = " from the string and turn the string into a float  */
/* Do this for line1, line2, line3 */
/* Example string is "  PERCENT FILLED =   6.72902E+00" need to turn this in to a float variable of value 6.72902 */

    return 0;

}

Answer 1

感谢您的帮助，我的代码现在可以正常工作，如下所示。我确信有一种更优雅的方法可以做到这一点，但为了完整起见，我将提供我的最终代码，以防它可以帮助别人。

    #include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main()
{
    char line[1000];
    char *pch;
    char c[] = "PERCENT FILLED =";
    char buff[1000];


/* Create a list of PERCENT FILLED values and write to file - copy every line containing PERCENT FILLED from p.out file*/
    FILE *fp = fopen("inputFILE.txt", "r");
    FILE *op = fopen("PERCENT_FILLED.txt", "w");

    if(fp == NULL || op == NULL)
       {
          fprintf(stderr, "Error opening file.");
          exit(1);
       }
    else 
       {
         while (fgets(line, sizeof(line), fp) != 0)
           {
              if((pch = strstr (line, c))!= 0)
              fprintf(op, "%s", line);
           }
       }

   fclose(fp);
   fclose(op);


/* Get the total number of lines in the file PERCENT_FILLED.txt   */

   FILE* myfile = fopen("PERCENT_FILLED.txt", "r");
   int ch, number_of_lines = 0;
   int line_num = 0;
   int count = 0;
   char readline[256];                                /* or other suitable maximum line size */
   char line1[256];
   char line2[256];
   char line3[256];

    do 
    {
        ch = fgetc(myfile);
        if(ch == '\n')
            number_of_lines++;
    } while (ch != EOF);

    // last line doesn't end with a new line!
    // but there has to be a line at least before the last line
    if(ch != '\n' && number_of_lines != 0) 
        number_of_lines++;

    fclose(myfile);




/* Get the last 3 PERCENT_FILLED values from the PERCENT_FILLED.txt   */


    FILE* infile = fopen("PERCENT_FILLED.txt", "r");

    if ( infile != NULL )
    {   
        while (fgets(readline, sizeof line, infile) != NULL) /* read a line */
        {   
            if (count == (number_of_lines-4))
            {   
               strcpy ( line3, readline);
               count++;
            }   
            else if (count == (number_of_lines-3))
            {  
               strcpy ( line2, readline);
               count++;
            }
            else if (count == (number_of_lines-2))
            {
               strcpy ( line1, readline);
               count++;
            }
            else
            {   
                count++;
            }   
        }   
        fclose(infile);
    }      

/* strip "PERCENT FILLED = " from the string and turn the string into a float  */
/* Do this for line1, line2, line3 */
/* Example string is "  PERCENT FILLED =   6.72902E+00" need to turn this in to a float varaible of value 6.72902 */

    char per1[7], fil1[6], eq1[1];
    char per2[7], fil2[6], eq2[1];
    char per3[7], fil3[6], eq3[1];
    float value1, value2, value3;

    sscanf (line1, "%s %s %s %E", per1, fil1, eq1, &value1 );
    sscanf (line2, "%s %s %s %E", per2, fil2, eq2, &value2 );
    sscanf (line3, "%s %s %s %E", per3, fil3, eq3, &value3 );

    printf("Value1: %f\n", value1 );
    printf("Value2: %f\n", value2 );    
    printf("Value3: %f\n", value3 );


    return 0;

    }