Question

In my software I have to read multiple txt databases in a serial way, so I read the first, then I do something with the info I got from that file, than I open another one to write and so on.

Sometimes I got an error on an opening OR creation of a file, and then I got errors on all the following opening/creation, which uses different functions, different variables, different files.

So for example I call the function below, which uses two files, and I got an error “* error while opening file -%s- ..\n”, then all the other fopen() in my code goes wrong!

This is an example of code for one single file:

FILE *filea;
if((filea=fopen(databaseTmp, "rb"))==NULL) {
    printf("* error while opening file -%s- ..\n",databaseTmp);
    fclose (filea);
    printf("---------- createDatabaseBackup ----------\n");
    return -1;
}
int emptyFolder=1;
FILE *fileb;
if((fileb=fopen(databaseBackup, "ab"))==NULL) {
    printf("* error while opening file -%s- ..\n",databaseBackup);
    fclose (fileb);
    printf("---------- createDatabaseBackup ----------\n");
    return -1;
}
else {
    int i=0;
    char c[500]="";
    for (i=0;fgets(c,500,filea);i++) {
        fprintf(fileb,"%s",c);
        emptyFolder=0;
    }
} 
fclose(fileb);
fclose(filea);

Answer 1

1. There is an upper limit on the number of open handles for a given process. May be you have a handle leak in your program ?

2. Error while creating a file typically means you don’t have access permission to the parent folder .

3. Those error log messages belong to your program . You can enhance it further. There is an errnum set by the os as fopen is essentially a system call. You can print that error number and get more info about your issue.