C examples

最近在看David R. Hanson 的《C Interfaces and Implementations》，文中第一章提到了Literate Programming

作者举了一个例子： 

功能：用于检测输入中相邻且相同的单词

#include<stdio.h>

#include<math.h>

#include<errno.h>

#include<stdlib.h>

#include<ctype.h>

#include<string.h>



int linenum;



int getword(FILE *,char *,int);

void doubleword(char *,FILE *);



int main(int argc,char *argv[]){



  int i;

  for(i=1; i<argc; i++){

    FILE *fp=fopen(argv[i],"r");

    if(fp==NULL){

      fprintf(stderr,"%s: can't open '%s'(%s)\n",argv[0],argv[i],strerror(errno));

      return EXIT_FAILURE;

    }else{

       doubleword(argv[i],fp);

       fclose(fp);

    }

  }

  if(argc==1) doubleword(NULL,stdin);

  return EXIT_SUCCESS;

}



int getword(FILE *fp, char *buf, int size){



  int c;

  c=getc(fp);

  for(; c!=EOF && isspace(c); c=getc(fp)) //scan forword to a nonspace character or EOF

    if(c=='\n')

      linenum++;

    else{                //copy the word into buf[0……size-1]

      int i=0;

      for(: c!=EOF && !isspace(c); c=getc(fp))

        if(i<size-1)    //size means the max length of any word int the text

          buf[i++]=tolower(c);

      if(i<size)

        buf[i]='\0';

    }



  if(c!=EOF)

    ungetc(c,fp);

  return buf[0]!='\0';



}



void doubleword(char *name,FILE *fp){

   char prev[128],word[128];

   linenum=1;

   prev[0]='\0';

   while(getword(fp,word,sizeof(word))){

      if(isalpha(word[0])&& strcmp(prev,wortd)==0){

          if(name)

            printf("%s:",name);

          printf("%d:%s\n",linenum,word);



       }



    }

}