The program does not want to read the file
this is my structure
typedef struct {
char mmsi[10];
char name[20];
double latitude;
double longitude;
int course;
double speed;
}Vessel;
this is my function that doesn't want to work
void searchByLatLong(double latitude, double longitude){
FILE * file;
struct dirent *drnt;
DIR * dir = opendir("./text");
char *path = (char *)malloc(19);
Vessel *vessel = (Vessel *)malloc(sizeof(Vessel));
while((drnt = readdir(dir)) != NULL) {
if(strcmp(drnt->d_name,".") && strcmp(drnt->d_name,"..")) {
strcpy(path,"text/");
strcat(path,drnt->d_name);
file=fopen(path, "r");
fscanf(file," %s %[a-zA-Z0-9 ]19s %lf %lf %d %lf", &vessel->mmsi,&vessel->name,&vessel->latitude,&vessel->longitude,&vessel->course,&vessel->speed);
// if (mmsi+".txt" == drnt->d_name){
printf("%s\n%s\n%lf\n%lf\n%d\n%lf\n\n",vessel->mmsi,vessel->name,vessel->latitude,vessel->longitude,vessel->course,vessel->speed);
//}
fclose(file);
}
seekdir(dir, telldir(dir));
// if(this->mmsi == mmsi){
// printVessel();
// }
}
closedir(dir);
}
When I try to load the txt file, it only loads the first two lines and then throws garbage out of memory after that. Loading data into other variables doesn't change anything; / This is an example txt file to be loaded:
3
RMS Titanic
22.222
33.333
4
5.9
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The problem is with your format string. Correct format string:
" %s %19[a-zA-Z0-9 ] %lf %lf %d %lf"
The width of the field before the conversion specifier. In addition, the sequence [...] is a conversion specifier, just like 's'. The problem you are seeing is what fscanf()
handles '3' because it matches the first %s
. It then processes "RMS Titanic" because it matches %[a-zA-Z0-9 ]
, but then processing stops because there is no "19" in the input. At this point, the rest of the arguments are uninitialized.
You should check the return value from fscanf()
. It will tell you how many conversions have actually been performed.
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Thank you for posting an interesting question; I learned about fscanf()
and the designation []
it takes.
The notation []
indicates that the string is being read, so the appended to it s
is considered a literal character to be matched. Likewise, the width specifier you specified 19
should appear before []
.
Your current code will start working if you have a ship named, for example, "RMS Titanic19s".
Change fscanf to:
fscanf(file," %s %19[a-zA-Z0-9 ] %lf %lf %d %lf",
vessel->mmsi,vessel->name,&vessel->latitude,
&vessel->longitude,&vessel->course,&vessel->speed);
and your code will start working.
Note that I fixed some compilation warnings, lose &
of char []
participants mmsi
and name
- they already point to a buffer that you want to fill. You don't need to &
face them. The pedagogical alternative form &vessel->mmsi[0]
is the address of the first character mmsi
.
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