我有一个使用strcmp
进行决策的功能,请参见下文:
void get_data(file_observational_area * _file_observational_area, int dimensions, int * start_indices, int * end_indices) {
char buffer[1024];
FILE *file;
size_t nread;
if (NULL != _file_observational_area) {
cout << "***_file_observational_area \n";
if (NULL != _file_observational_area->_file) {
//if the data is in a file
cout << "****_file_observational_area->_file \n";
cout << "***_file_observational_area->_file->local_identifier:" << _file_observational_area->_file->local_identifier << "\n";
cout << "***_file_observational_area->_file->file_name:" << _file_observational_area->_file->file_name << "\n";
cout << "***data_file_local_identifier:" << data_file_local_identifier << "\n";
if (strcmp(_file_observational_area->_file->local_identifier, data_file_local_identifier) == 1) {
if (NULL != _file_observational_area->_file->file_name) {
//open the file
file = fopen(_file_observational_area->_file->file_name, "r");
if (file) {
while ((nread = fread(buffer, 1, sizeof (buffer), file)) > 0)
cout << buffer << "\n";
if (ferror(file)) {
/* deal with error */
}
}
}
} else {
cout << "***_file_observational_area NOT A file \n";
}
if (NULL != file) {
fclose(file);
file = NULL;
}
}
}
}
用于比较的data_file_local_identifier在struct中定义:
#ifndef DATA_FILE__H
#define DATA_FILE__H
#define data_file_local_identifier "file"
struct data_file
{
char * file_name;
char * local_identifier;
};
typedef struct data_file data_file;
#endif /* DATA_FILE__H */
程序输出代码段:
****_file_observational_area->_file
***_file_observational_area->_file->local_identifier:file
***_file_observational_area->_file->file_name:A0087_0008_597249118_597252671_181130002623_eu.csv
***data_file_local_identifier:file
***_file_observational_area NOT A file
在此代码行上方的get_data函数中:
if (strcmp(_file_observational_area->_file->local_identifier, data_file_local_identifier) == 1)
返回false而不是true,尽管如果您查看输出,则两个字符串都是“文件”。那为什么失败了?
strcmp
返回0 if strings are equal, or a number whose sign represents which is "smaller":返回指示字符串之间关系的整数值:
<0第一个不匹配的字符在ptr1中的值比在ptr2中的值低0两个字符串的内容相等
> 0与ptr2中不匹配的第一个字符在ptr1中具有更大的值
0