How to fix &localtime in .txt - C - c

Question

I want to implement a function in my program that sends a .txt to my email with some tasks that i have to do in the day. Here's the code:
void txtCreator(){
/**file.dat and file.txt, respectively**/
FILE *fp, *fp1;
/**struct that contain the events**/
struct evento *display = (struct evento *)malloc(sizeof(struct evento));
char buffer[48];
char email_events[] = {"dd_mm.txt"};//filename.txt
char msg[]={"Nao ha eventos disponiveis para hoje!\n"};
int count=0;
time_t rawtime;
time(&rawtime);
struct tm timenow = *localtime(&rawtime);
strftime(buffer, 48, "%d_%m", &timenow);
fp = fopen(file_name, "rb");
fp1 = fopen(email_events, "w");
if(strcmp(buffer, email_events)!=0){
strcpy(email_events, buffer);
while(fread(display, sizeof(struct evento), 1, fp)==1){
if (feof(fp) || fp==NULL){
break;
}
else if(display->dia==timenow.tm_mday && display->mes==timenow.tm_mon+1){
fwrite(display, sizeof(struct evento), 1, fp1);
fprintf(fp1, "%s", "\n");
count++;
}
}
}
if(count==0){
fprintf(fp1, "%s", msg);
}
fclose(fp);
fclose(fp1);
}
Everything is working just fine, but there's two problems:
1-
strcpy(email_events, buffer);
is not working, and:
2-
when i create the .txt file, it shows like that:
test ¹0(¹€(.v™ ™­ °'¹8¹uguese_Brazil.12
it shows the event name (test) correctly, but the date is not working.
I've tried a lot of things, but nothing works.
Sorry for the bad english, not my native language.

Answer 1

when i create the .txt file, it shows like that:
test ¹0(¹€(.v™ ™­ °'¹8¹uguese_Brazil.12
Let's address this first: you're not writing text to your .txt file. You're writing a struct. It's going to look like garbage.
For example, let's say display->dia is 19. This means the number 19 will be written to the file, not the text 19, the number 19. Read as text, 19 is garbage. 10 is a newline. 65 is A.
If your intent is to dump the structs into a file, assuming struct evento has no pointers, you're good. In fact you probably shouldn't add a newline, it will interfere with reading the file by the size of the struct.
If your intent is to produce a human readable text file, you need to translate each piece of the struct into text. For example, if you wanted to write the day and month as text...
fprintf(fp1, "%d_%d", display->dia, display->mes);
I'll assume that going forward.
strcpy(email_events, buffer); is not working
At first glance it looks like your strcpy is backwards, it's strcpy(src, dest) and presumably you want to copy email_events into buffer: strcpy(buffer, email_events).
Looking further, your code does nothing with either buffer nor email_events after that. The strcpy is pointless.
Going even further, buffer is the month and day like 07_19. email_events is always dd_mm.txt. Those will never match. strcmp(buffer, email_events)!=0 will always be true making the if check pointless.
I'm not sure what the intent of buffer and email_events are, but it appears to be trying to create a filename based on the current date? This can be done much simpler with one better named variable outfile.
time_t rawtime;
time(&rawtime);
struct tm timenow = *localtime(&rawtime);
char outfile[20];
strftime(outfile, 20, "%d_%m.txt", &timenow);
Moving along to other problems, you don't check that fp1 opened.
You do eventually check fp but you check it after you've already read from a possibly null file pointer. If you're compiling with an address sanitizer (which you should) it will cause an error. Causing an error when using a null pointer is good, it will solve many a mystery memory problem for you.
It's much easier and robust and address sanitizer friendly to check immediately. We can also do a better job naming them to avoid confusing the input from the output: in and out.
FILE *in = fopen(file_name, "rb");
if( in == NULL ) {
perror(file_name);
exit(1);
}
And since you're reading binary with rb you should be writing binary you should be using wb. This only matters on Windows, but might as well be consistent.
FILE *out = fopen(outfile, "wb");
if( out == NULL ) {
perror(outfile);
exit(1);
}
There's no need to check feof(fp), while(fread(display, sizeof(struct evento), 1, fp)==1) will already exit the loop at end of file when it fails to read. In general, explicitly checking for the end of file leads to subtle problems.
The read/write loop is now much simpler.
while(fread(display, sizeof(struct evento), 1, in)==1){
if(display->dia==timenow.tm_mday && display->mes==timenow.tm_mon+1) {
fprintf(out, "%d_%d\n", display->dia, display->mes);
count++;
}
}
Putting it all together...
void txtCreator(){
const char *no_events_found_msg = "Nao ha eventos disponiveis para hoje!\n";
// No need to cast the result of malloc, it just invites mistakes.
struct evento *display = malloc(sizeof(struct evento));
// Generate the output filename directly, no strcmp and strcpy necessary.
time_t rawtime;
time(&rawtime);
struct tm timenow = *localtime(&rawtime);
char outfile[20];
strftime(outfile, 48, "%d_%m.txt", &timenow);
// Immediatetly make sure the files are open and error immediately.
FILE *in = fopen(file_name, "rb");
if( in == NULL ) {
perror(file_name);
exit(1);
}
FILE *out = fopen(outfile, "wb");
if( out == NULL ) {
perror(outfile);
exit(1);
}
// Now that we know the files are open, reading and writing is much simpler.
int count=0;
while(fread(display, sizeof(struct evento), 1, in)==1){
if(display->dia==timenow.tm_mday && display->mes==timenow.tm_mon+1) {
fprintf(out, "%d_%d\n", display->dia, display->mes);
count++;
}
}
if(count==0){
fprintf(out, "%s", no_events_found_msg);
}
fclose(in);
fclose(out);
}
Note that I've used a style which declares variables in place. This makes the code easier to read, limits the scope of each variable, and it avoids declaring variables which you never use.

Answer 2

Assuming that you are meaning to copy email_events into your buffer (since you assigned a static string), your strcpy parameters are backwards.
Below is the declaration of strcpy
char *strcpy(char *dest, const char *src);
You probably meant:
strcpy(buffer, email_events);