问题描述
struct Book {
char *title;
char *authors;
unsigned int year;
unsigned int copies;
};
int existance_of_book(char title[])
{
char string[30];
ptr_to_library = fopen("library.txt","r");
if(ptr_to_library == NULL)
{
printf("\nERROR: cannot open file\n");
return -1;
}
while (fgets(title,sizeof(title),ptr_to_library) != NULL)
{
if(strstr(string,title)!=0)
{
printf("book found\n");
return 1;
}
}
return 0;
}
我正在尝试在文件中搜索字符串,但由于我要搜索的字符串中有空格,因此该函数无法找到该字符串。例如,如果 .txt 文件中的字符串为“hello”,而在函数中输入的字符串为“he”,则此函数也会找到匹配项。即使有空格,有没有办法在文件中搜索确切的字符串
解决方法
使用 strstr
查找子字符串。
检查子字符串是否位于行首或前面有标点符号或空格。
还要检查子字符串是否位于行尾或以标点符号或空格结尾。
如果使用 fgets
获取要查找的子字符串,请务必使用 strcspn
删除尾随的换行符。在文件的行中,尾部的换行符应该无关紧要,但此代码使用 strcspn
将其删除。
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#define SIZE 1024
int main ( void) {
char find[SIZE] = "he";
char line[SIZE] = "";
char const *filename = "library.txt";
char *match = NULL;
FILE *pf = NULL;
if ( NULL == ( pf = fopen ( filename,"r"))) {
perror ( filename);
exit ( EXIT_FAILURE);
}
int length = strlen ( find);
while ( fgets ( line,SIZE,pf)) {//read lines until end of file
line[strcspn ( line,"\n")] = 0;//remove newline
char *temp = line;
while ( ( match = strstr ( temp,find))) {//look for matches
if ( match == line //first of line
|| ispunct ( (unsigned char)*(match - 1))
|| isspace ( (unsigned char)*(match - 1))) {
if ( 0 == *(match + length)//end of line
|| ispunct ( (unsigned char)*(match + length))
|| isspace ( (unsigned char)*(match + length))) {
printf ( "found %s in %s\n",find,line);
break;//found a match
}
}
temp = match + 1;//advance temp and check again for matches.
}
}
fclose ( pf);
return 0;
}