[英]read lines from file with fgets and compare each line with strncmp in c
我想从看起来像这样的文件中读取每一行:
readEveryLine
{
"Bart [m]" -> "Marge [f]";
"Lisa [f]" -> "Homer [m]";
...
}
我想使用:
我有的:
while(fgets(*file_string, MAX_INPUT_STDIN, file) != NULL)
{
changeLastC(*file_string); // function to change \n into \0
if (strncmp(*file_string, "readEveryLine\0", 14) == 0)
{
if (strncmp(*file_string, "{\0", 2) == 0)
{
// check the first -> relation
}
}
else
{
printf("Error Parsing\n");
}
}
所以问题是它只是给我一个错误解析,而我不知道我在这里做错了什么。
非常感谢您的帮助!
在这里,我现在做了几件事(现在解析前两行就可以了):也许有人为我提供了一个很好的提示,告诉我我可以做得更好。 非常感谢。
if ((fp = fopen("df.dot","r")) == NULL)
{
printf("Error: File Open\n");
return 1;
}
int row = 0; // check row 1
while (fgets(buffer, MAX_PARSING, fp))
{
if ((row == 0) && strncmp(buffer, "readEveryLine\n", 14) == 0)
{
printf("%s", buffer);
}
else
{
printf("Parsing Error 1\n");
}
}
int row1 = 1; // check row 2
while (fgets(buffer, MAX_PARSING, fp))
{
if ((row1 == 1) && strncmp(buffer, "{\n", 2) == 0)
{
printf("%s", buffer);
}
else
{
printf("Parsing Error 2\n");
}
}
int row2 = 2; // check other rows (dynamic, could be even more or less)
while (fgets(buffer, MAX_PARSING, fp))
{
if ((row2 == 2) && strncmp(buffer, " ", 2) == 0)
{
const char *p1 = strstr(fp, "\"")+1;
const char *p2 = strstr(p1, " [m]\"");
const char *p3 = strstr(p1, " [f]\"");
// extract male persons
if (p1 && p2)
{
size_t len1 = p2 - p1;
char* res1 = (char*)malloc(sizeof(char)*(len1 + 1));
strncpy(res1, p1, len1);
res1[len1] = '\0';
// give res1 for functionMale() to work on that string
}
// extract female persons
else if (p1 && p3)
{
size_t len2 = p3 - p1;
char* res2 = (char*)malloc(sizeof(char)*(len2 + 1));
strncpy(res2, p1, len2);
res2[len2] = '\0';
// give res2 for functionFemale() to work on that string
}
else if (strcmp(buffer, " -> ") == 0)
{
// work in progress (quite complicated to do this i think)
// it has to be a realtion between two people
}
else if (strcmp(buffer, ";") == 0)
{
// work in progress
// this sign can either exist like this:
// "Bart [m]" -> "Marge [f]";
// or like this:
// "Marge [f]";
}
break;
}
else
{
printf("Parsing Error 3\n");
}
row2++;
}
//,最后一个符号必须是} \\ n
您的算法已损坏。 您使用*file_string
相同内容将其与两个不同的字符串进行比较。 如果找到"readEveryLine"
的匹配项,则需要从文件中读取下一行,然后才能获取strncmp()
的下一个匹配strncmp()
。 否则,文件中的行必须同时匹配"readEveryLine"
和 "{"
以传递第二个if
条件,这是不可能的。
编辑:现在,您已经做了一些改进,但我仍然认为它不适用于您的方法。 循环不会在应有的情况下退出,并且if-else-cascade似乎也不是一个好主意。 在您的方法中,您会被读取太多的行弄得一团糟,而只能解析1行。
也许您应该阅读一些有关状态机的信息。
这是解决问题的一种快速方法:
enum { STATE_HEADER1, STATE_HEADER2, STATE_BODY, STATE_END} state;
int done = 0;
state = STATE_HEADER1;
while (fgets(buffer, MAX_PARSING, fp) && !done) {
if (state == STATE_HEADER1) {
if (strcmp(buffer, "readEveryLine\n") == 0) {
printf("%s", buffer);
state = STATE_HEADER2;
}
else {
printf("Parsing Error 1\n");
done = 1;
}
}
else if (state == STATE_HEADER2) {
if (strcmp(buffer, "{\n") == 0) {
printf("%s", buffer);
state = STATE_BODY;
}
else {
printf("Parsing Error 2\n");
done = 1;
}
}
else if (state == STATE_BODY) {
if (strcmp(buffer, " ") == 0) {
const char *p1 = strstr(buffer, "\"");
const char *pm = strstr(p1, " [m]\"");
const char *pf = strstr(p1, " [f]\"");
char *res;
const char *ptemp;
int is_male;
if (p1 && pf) {
p1 ++;
is_male = 0;
size_t len1 = pf - p1;
res = malloc(len1 + 1);
strcpy(res, p1);
ptemp = pf+3; // point after closing \"
// give res for functionFemale() to work on that string
}
else if (p1 && pm) {
p1 ++;
is_male = 1;
size_t len1 = pm - p1;
res = malloc(len1 + 1);
strcpy(res, p1);
ptemp = pm+3; // point after closing \"
// give res for functionMale() to work on that string
}
else {
done = 1;
printf("Parsing Error 2\n");
}
// Now we have res and is_male holding name and gender.
if (!done)
{
if (strncmp(ptemp, " -> ", 4) == 0) {
// Handle this variant:
// this sign can either exist like this:
// "Bart [m]" -> "Marge [f]";
// Do similar stuff as above for first name
// Get second name + gender
// Also check trailing ';' here
}
else if (strcmp(temp, ";\n") == 0) {
// Handle this variant:
// or like this:
// "Marge [f]";
}
} // found " "
else {
if (strcmp(buffer, "}\n") == 0) {
state = STATE_END;
done = 1;
printf("That's it folks...\n");
}
else {
done = 1;
printf("Parsing Error 3\n");
}
}
}
} // STATE_BODY
} // while (fgets)
if (state == STATE_END) }
// Success. :)
} else {
// Something didn't match.
}
// close file, cleanup, etc.
我还没有编译它,但是您应该明白这一点。
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