[英]searching for EXACT string with spaces in . txt file from C program
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;
}
我正在嘗試在文件中搜索字符串,但由於我要搜索的字符串中有一個空格,因此 function 無法找到該字符串。 此 function 也會找到匹配項,例如,如果 .txt 文件中的字符串讀取“hello”,並且 function 中輸入的字符串是“he”。 即使有空格,有沒有辦法在文件中搜索確切的字符串
使用strstr
查找子字符串。
檢查子字符串是否位於行首或前面有標點符號或空格。
還要檢查子字符串是否位於行尾或以標點符號或空格結尾。
如果使用fgets
獲取要查找的子字符串,請務必使用strcspn
刪除尾隨的換行符。 在文件的行中,尾隨換行符無關緊要,但此代碼使用strcspn
將其刪除。
#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;
}
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