Strtok 无法正常读取多行字符串

Question

所以，我正在使用词法分析器，在所有的 flex 恶作剧之后我得到了这个文本：

ISEP 1252 "ADDRESS"
"Name1" 1253 "INFORMATICA"
"Name2" 1254 "Boilerplate1"
"Name3" 1255 "Boilerplate2"
"Name4" 1256 "Boilerplate3"
"Name5" 1257 "Boilerplate4"
"Name6" 1258 "Boilerplate5"

并将其存储在

yytext

中，然后使用

strtok

将每一行和该行的内容分开：

// get first line
char* line = strtok(yytext, "\n");
// get school name
char* schoolName = strtok(line, " \t");
// get school num students
int schoolNumStudents = atoi(strtok(NULL, " \t"));
// get school address inside the quotes
char* schoolAddress = strtok(NULL, "\"");

strcpy(schools[schoolCount].name, schoolName);
schools[schoolCount].numStudents = schoolNumStudents;
strcpy(schools[schoolCount].address, schoolAddress);
//print school[schoolCount]
printf("Escola: %s\n", schools[schoolCount].name);
printf("Num alunos: %d\n", schools[schoolCount].numStudents);
printf("Morada: %s\n", schools[schoolCount].address);

// get teachers
line = strtok(NULL, "\n");
while (line != NULL) {
    char* teacherName = strtok(line, "\"");
    int teacherExt = atoi(strtok(NULL, " \t"));
    char* teacherDepartment = strtok(NULL, "\"");

    schools[schoolCount].numTeachers++;
    if(schools[schoolCount].teachers == NULL) {
        schools[schoolCount].teachers = (struct Teacher*) malloc(sizeof(struct Teacher));
    }
    else {
        schools[schoolCount].teachers = (struct Teacher*) realloc(schools[schoolCount].teachers, sizeof(struct Teacher) * (schools[schoolCount].numTeachers));
    }

    printf("Nome: %s\n", teacherName);
    printf("Ext: %d\n", teacherExt);
    printf("Departamento: %s\n", teacherDepartment);
    line = strtok(NULL, "\n");
}

schoolCount++;

这里要看到的是，作为我提供的字符串

yytext

，第二个

strtok(NULL, "\n")

返回

NULL

而不是第二行。有什么我想念的吗？

PS：除了我提供的代码之外，没有任何与C相关的代码，代码块嵌套在lex规则中。

我尝试将 yytext 的内容复制到另一个变量，因为 strtok 改变了变量并且 yytext 保留给 lex，这没有完成任何事情，我尝试清除 strtok 缓冲区并在第二行开始重试 strtok，也没有'没用。

Answer 1

问题是在为子字符串行调用

strtok

之后

char* line = strtok(yytext, "\n");
// get school name
char* schoolName = strtok(line, " \t");
//..

函数

strtok

在数组

line

中保留一个指针。所以下一次调用 strtik

line = strtok(NULL, "\n");

指的是

line

而不是

yytext

。

避免该问题的一种方法是计算 存储在

line

中的字符串，例如

char *pos = yytext;

char* line = strtok( pos, "\n");
size_t n = strlen( line );
//...

并将该值用作数组

yytext

内的偏移量，用于数组

strtok

的下一次调用

yytext

pos += n;
line = strtok( pos, "\n");
//...