如何将值动态分配给结构 [英] How to assign values dynamically to a struct
问题描述
我对如何访问和更改结构的值感到困惑。该程序接收一些外部文件，并对每个字符串进行标记，然后将其归类为以下气候信息字段。外部文件如下所示：
I am stumped as to how to access and change the values of a struct. The program takes in some external files and tokenized each string and categorizes them in the following fields of climate info. The external files look something like this:
TDV格式：
TN 1424325600000 dn20t1kz0xrz 67.0 0.0 0.0 0.0 101872.0 262.5665
TN 1422770400000 dn2dcstxsf5b 23.0 0.0 100.0 0.0 100576.0 277.8087
TN 1422792000000 dn2sdp6pbb5b 96.0 0.0 100.0 0.0 100117.0 278.49207
TN 1422748800000 dn2fjteh8e80 6.0 0.0 100.0 0.0 100661.0 278.28485
TN 1423396800000 dn2k0y7ffcup 14.0 0.0 100.0 0.0 100176.0 282.02142
列的顺序是第一个是对于状态码，第二个用于时间戳（自Unix纪元以来的毫秒数），第三列是位置的geohash字符串（未使用），第四列是湿度百分比，第五列是有雪（值0.0或1.0），第六列是覆盖率百分比，第七是雷击次数，第八是压力（单位未知，bu t数据未使用，所以没关系），第九是表面温度（以开尔文为单位）。我确实意识到必须转换时间戳记和表面温度，因此我对此并不担心。我需要汇总整个状态下的数据（与geohash无关），跟踪最低和最高温度以及它们发生的时间，并统计该状态的记录数，以便可以对值进行平均。
The columns are in order such that the first is for state code, the second for timestamp (in milliseconds since the Unix epoch), the third column is geohash string for the location (unused), the fourth is percentage humidity, the fifth is snow present (values 0.0 or 1.0), the sixth is percentage cloud cover, the seventh is number of lightning strikes, the eighth is pressure (units unknown, but the data is unused so it doesn't matter) and the ninth is surface temperature (measured in Kelvin). I do realize I must convert the timestamp and surface temperature, so I am not worried about that. I need to aggregate the data across a complete state (regardless of geohash), keeping track of the minimum and maximum temperatures and the time when they occurred, and counting the number of records for the state so that values can be averaged.
单个状态的输出应如下所示：
The output for a single state should look like this:
* Opening file: data_tn.tdv
* States found: TN
* -- State: TN --
* Number of Records: 17097
* Average Humidity: 49.4%
* Average Temperature: 58.3F
* Max Temperature: 110.4F on Mon Aug 3 11:00:00 2015
* Min Temperature: -11.1F on Fri Feb 20 04:00:00 2015
* Lightning Strikes: 781
* Records with Snow Cover: 107
* Average Cloud Cover: 53.0%
但是，会有多个状态，每个状态都有要处理的数据文件。
However, there will be multiple states, each with its own data file to be processed.
如您所见，第一个令牌将被分配到州代码，但是我不知道如何执行此操作。我尝试了许多strcpy和许多其他方法来尝试将令牌发送到各自的字段中，但是没有一种有效。
As you can see, the first token will be assigned to the state code however I have no idea as to how to do this. I have tried numerous strcpy and numerous other methods to try to send token into their respective fields but none have worked.
struct climate_info
{
char code[3];
unsigned long num_records;
unsigned long timestamp;
char location[13];
unsigned int humidity;
int snow;
unsigned int cover;
int strikes;
long double pressure;
long double sum_temperature;
};
struct stats
{
char code[3];
long long timestamp;
double humidity;
double snow;
double cloud;
double strikes;
double sum_temperature;
}stats;
void analyze_file(FILE *file, struct climate_info *states[], int num_states);
void print_report(struct climate_info *states[], int num_states);
int main(int argc, char *argv[])
{
/* TODO: fix this conditional. You should be able to read multiple files. */
if (argc < 1 )
{
printf("Usage: %s tdv_file1 tdv_file2 ... tdv_fileN \n", argv[0]);
return EXIT_FAILURE;
}
/* Let's create an array to store our state data in. As we know, there are
* 50 US states. */
struct climate_info *states[NUM_STATES] = { NULL };
int i;
for (i = 1; i < argc; ++i)
{
/* TODO: Open the file for reading */
/* TODO: If the file doesn't exist, print an error message and move on
* to the next file. */
/* TODO: Analyze the file */
/* analyze_file(file, states, NUM_STATES); */
FILE *fp = fopen(argv[i], "r");
if(fp == NULL)
{
printf("Error opening file");
break;
}
else if(fp)
{
analyze_file(fp, states,NUM_STATES);
}
fclose(fp);
}
print_report(states, NUM_STATES);
return 0;
}
void analyze_file(FILE *file, struct climate_info **states, int num_states)
{
const int line_sz = 100;
char line[line_sz];
int counter = 0;
char *token;
while (fgets(line, line_sz, file) != NULL)
{
/* TODO: We need to do a few things here:
*
* * Tokenize the line.
* * Determine what state the line is for. This will be the state
* code, stored as our first token.
* * If our states array doesn't have a climate_info entry for
* this state, then we need to allocate memory for it and put it
* in the next open place in the array. Otherwise, we reuse the
* existing entry.
* * Update the climate_info structure as necessary.
*/
struct climate_info *y = malloc(sizeof(struct climate_info)*num_states);
token = strtok(line," \t");
strcpy((y[counter]).code,token);
counter++;
printf("%s\n",token);
while(token)
{
printf("token: %s\n", token);
token = strtok(NULL, " \t");
}
printf("%d\n",counter);
//free(states);
}
void print_report(struct climate_info *states[], int num_states)
{
printf("States found: ");
int i;
for (i = 0; i < num_states; ++i) {
if (states[i] != NULL)
{
struct climate_info *info = states[i];
printf("%s", info->code);
}
}
printf("\n");
推荐答案
不应分配从文件读取的值直接指向结构的元素。您需要一组变量（它们可以在结构中，但不是必需的）以在读取数据时接收数据，并使用 sscanf（）进行解析并分裂。然后，您可以验证状态码是否正确，时间是否合理等等。然后，您将累积信息添加到统计结构中，该结构与您当前拥有的结构climate_info 相关但又不同。例如，它不需要Geohash列或压力列，但是需要确定最低温度和时间，以及确定最高温度和时间。您可以累计积雪数量，雷击数量，湿度和云量以及当前温度。然后，当您完成文件时，可以平均温度，湿度和云量值，并且可以打印聚合。
The values read from the file shouldn't be assigned directly to elements of the structure. You need one set of variables (they could be in a structure, but it isn't necessary) to receive the data as it is read, with sscanf() doing the parsing and splitting up. You then validate that the state code is correct, that the time is plausible, and so on. Then you add the cumulative information into the 'statistics structure', which is related to but different from the struct climate_info you currently have. It doesn't need a geohash column, for example, or a pressure column, but does need a minimum temperature and a time when that was spotted, and a maximum temperature and the time when that was spotted. You accumulate the snow cover count, and the lightning strike count, and the humidity and cloud cover and current temperature. Then when you finish the file, you can average the temperature, humidity and cloud cover values, and you can print the aggregates.
由于您明智地使用 fgets（）从文件中读取行（请勿更改！），应使用 sscanf（）来解析行。您需要：
Since you are sensibly using fgets() to read lines from the file (don't change that!), you should use sscanf() to parse the line. You need:
- 州代码（
char state [3];）， - 一个时间值（
很长的毫秒；）， - 一个湿度值（
双重湿度；）， - 降雪礼物值（
双雪；，因为格式是浮点数）， - 云量值（
双重云；）， - 雷击值（
双重闪电）， - 和温度值（
双重温度；）。
- a state code (
char state[3];), - a time value (
long long millitime;), - a humidity value (
double humidity;), - a 'snow present' value (
double snow;since the format is a floating point number), - a 'cloud cover' value (
double cloud;), - a lightning strikes value (
double lightning), - and a temperature value (
double temperature;).
然后使用
if (sscanf(line, "%2[A-Z] %lld %*s %lf %lf %lf %lf %*lf %lf",
state, &millitime, &humidity, &snow, &cloud, &lightning, &temperature) == 7)
{
…validate data and report errors if appropriate…
…stash values appropriately; increment the count…
}
else
{
…report format error?…
}
请注意，格式中的 * 会禁止分配；该列已读取但被忽略。代码检查压力是否为数字列。它不会验证必须存在之外的geohash列。可以将大小指定为上限％* 12s 。
Note that the * in the formats suppresses the assignment; the column is read but ignored. The code checks that the pressure is a numeric column; it doesn't validate the geohash column beyond 'it must exist'. It would be possible to specify the size as an upper bound %*12s.
使用 fgets（）和 sscanf（）可以更清楚地报告错误-您可以说状态XXX：行中的代码不正确，然后打印该行，因为您仍然可以使用它。使用 fscanf（），您将无法如此轻松地就行内容进行报告，这使调试数据的人变得更加困难。
One of the many advantages of using fgets() and sscanf() is that you can report errors much more intelligibly — you can say "the state code was incorrect in line XXX:" and then print the line since you have it available still. Using fscanf(), you'd not be able to report so easily on the content of the line, which makes it harder for whoever is debugging the data.
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