the function fgetc is not working properly - c

Question

i'm testing the fgetc() function but it doesn't work properly (i have used this function befor so i know how it works)
#include <stdio.h>
#include <stdlib.h>
int main()
{
FILE *file = NULL;
int n;
file = fopen("test.txt", "w+");
if(file != NULL)
{
fputs("ab", file);
printf("%c", fgetc(file));
}
else
{
printf("error");
}
return 0;
}
the output should be "a" but it's somthing else

Answer 1

The file is opened for both writing and reading but you need to fseek to the correct place in the file (here, the beginning). In particular, when switching between writing and reading you need to fseek or fflush.
When the "r+", "w+", or "a+" access type is specified, both reading
and writing are enabled (the file is said to be open for "update").
However, when you switch from reading to writing, the input operation
must encounter an EOF marker. If there is no EOF, you must use an
intervening call to a file positioning function. The file positioning
functions are fsetpos, fseek, and rewind. When you switch from writing
to reading, you must use an intervening call to either fflush or to a
file positioning function.
In any case, after writing to the file, the file pointer is in the wrong place to read what was just written.
So the code becomes
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
FILE *file = NULL;
file = fopen("test.txt", "w+");
if(file != NULL) {
fputs("ab", file);
fseek(file, 0, SEEK_SET);
printf("%c", fgetc(file));
fclose(file);
}
else {
printf("error");
}
return 0;
}
And if you want to continue writing to the file, you must fseek to its end.

Answer 2

Your error is that you are trying to read a file that has been opened for writting. You should write inside it, then close the file and reopen it for reading. This code will show what I am telling:
#include<stdio.h>
#include<stdlib.h>
int main()
{
FILE *fileRead, *fileWrite = NULL;
int n;
fileWrite = fopen("test.txt", "w+");
if(fileWrite != NULL)
{
fputs("ab", fileWrite);
fclose(fileWrite);
}
else
{
printf("error");
}
// Open again the file for read
fileRead = fopen("test.txt", "r");
printf("%c", fgetc(fileRead));
fclose(fileWrite);
// End function
return 0;
}