fgets读取如何换行呢

2013-07-09

fgets读取怎么换行呢？本帖最后由 Smilencetion 于 2012-02-27 17:28:14 编辑程序接受两个命令行参数，第一

fgets读取怎么换行呢？
本帖最后由 Smilencetion 于 2012-02-27 17:28:14 编辑程序接受两个命令行参数，第一个是一个字符，第二个是文件名
要求程序只打印文件中包含给定字符的那些行


#include <stdio.h>
#include <stdlib.h>
#define MAX 256
int has_ch(char ,const char *);
int main(int argc,char *argv[])
{
      FILE *fp;char arr[MAX],ch;
      if(argc!=3)
      {
            printf("no enough arguments:");
            exit(EXIT_FAILURE);
      }
      ch=argv[1][0];
      if((fp=fopen(argv[2],"r"))==NULL)
      {
            printf("can't open %s",argv[2]);
            exit(1);
      }
      while(fgets(arr,MAX,fp)!=NULL)
      {
            if(has_ch(ch,arr))
                  fputs(arr,stdout);
      }
      fclose(fp);
      return 0;
}
int has_ch(char ch,const char *arr)
{
      while(*arr)
            if(ch==*arr++)
            return 1;
      return 0;
}

我编译好后再命令行输入 test.exe a txt.txt
其中txt.txt内容为
adsf
dfdfde
asff
adfdfdf

我想问的是

   while(fgets(arr,MAX,fp)!=NULL)
      {
            if(has_ch(ch,arr))
                  fputs(arr,stdout);
      }

是怎么一行一行读取字符串的
当执行第2次 while(fgets(arr,MAX,fp)!=NULL)，fgets是怎么变为从txt.txt第2行开始读取的？还是其他情况
[解决办法]
char * fgets ( char * str, int num, FILE * stream );
Get string from stream

Reads characters from stream and stores them as a C string into str until (num-1) characters have been read or either a newline or a the End-of-File is reached, whichever comes first.
A newline character makes fgets stop reading, but it is considered a valid character and therefore it is included in the string copied to str.
A null character is automatically appended in str after the characters read to signal the end of the C string.

------解决方案--------------------

引用:

引用:

char * fgets ( char * str, int num, FILE * stream );
Get string from stream

Reads characters from stream and stores them as a C string into str until (num-1) characters ha……

是的！

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fgets读取如何换行呢