c - 如何在C中将文件中每一行的首字母设为大写

Question

在 text.txt 文件中，我有一些行，例如“Apples are red.guavas are green.lemons are yellow”。我想要新行中的第一个字母( Guava 中的 g，柠檬中的 l 大写)。但是文件中的输出是相同的...

#include<stdio.h>
main()
{
  FILE *p;
  char c;
  int i;
  int end_of_line=0;
  p=fopen("text.txt","r+");//opening file for reading & writing.

  while(c!=EOF)
  {
    c=fgetc(p);
    if(end_of_line==1) // if it is a new line
    if (islower(c)!=0) // and if the first letter is small
      fputc(toupper(c),p); //change the small to capital
    if(c=='.')
      end_of_line=1;
    else
      end_of_line=0;
  }
  fseek( p, 0, SEEK_SET ); //setting the file pointer to the start of file
  while((c=fgetc(p))!=EOF)
    printf("%c",c);
  fclose(p);
}

Answer 1

For files open for update (those which include a "+" sign), on which both input and output operations are allowed, the stream should be flushed (fflush) or repositioned (fseek, fsetpos, rewind) between either a writing operation followed by a reading operation or a reading operation which did not reach the end-of-file followed by a writing operation.

我通过在行前后使用 ftell anf fseek 让你的示例工作:

fputc(toupper(c),p);