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Q&A Why does fopen return NULL?

#include<stdio.h> #include<stdlib.h> int main (void){ FILE *cfPtr; char name[15]; int ID; if ((cfPtr = fopen("draft.txt","w")) == NULL){ printf("File could n...

2 answers · posted 3y ago by dumplings‭ · edited 2y ago by dumplings‭

Question c file-handling stdio fopen

#8: Post edited by

dumplings‭ · 2022-06-26T14:20:36Z (over 2 years ago)

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```c
#include<stdio.h>
#include<stdlib.h>
int main (void){
FILE *cfPtr;
char name[15];
int ID;
~~if ((cfPtr = fopen("students.txt","w")) == NULL){~~
printf("File could not be opened...\n"); //program gives me this as an output
}
~~else { //I want the output to be those in this else statement~~
~~do {~~
~~printf("Enter Name:\n");~~
~~fflush(stdin); //flushing the input~~
~~scanf("%s", name);~~
~~printf("Enter Student Number:");~~
~~scanf("%d", &ID);~~
~~fprintf(cfPtr, "%d %s\n", ID, name);~~
~~} while (ID != -1);~~
~~fclose(cfPtr);~~
}
~~return 0;~~
}
```
Output:
> File could not be opened...

```c
#include<stdio.h>
#include<stdlib.h>
int main (void){
FILE *cfPtr;
char name[15];
int ID;
if ((cfPtr = fopen("draft.txt","w")) == NULL){
printf("File could not be opened...\n"); //program gives me this as an output
}
}
```
Output:
> File could not be opened...

c file-handling stdio fopen

#7: Post edited by

hkotsubo‭ · 2021-12-07T13:41:06Z (almost 3 years ago)
Missed one extra backtick in code block, now it should be correct

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Why does fopen return NULL?

~~````c~~
#include<stdio.h>
#include<stdlib.h>
int main (void){
FILE *cfPtr;
char name[15];
int ID;
if ((cfPtr = fopen("students.txt","w")) == NULL){
printf("File could not be opened...\n"); //program gives me this as an output
}
else { //I want the output to be those in this else statement
do {
printf("Enter Name:\n");
fflush(stdin); //flushing the input
scanf("%s", name);
printf("Enter Student Number:");
scanf("%d", &ID);
fprintf(cfPtr, "%d %s\n", ID, name);
} while (ID != -1);
fclose(cfPtr);
}
return 0;
}
```
Output:
> File could not be opened...

```c
#include<stdio.h>
#include<stdlib.h>
int main (void){
FILE *cfPtr;
char name[15];
int ID;
if ((cfPtr = fopen("students.txt","w")) == NULL){
printf("File could not be opened...\n"); //program gives me this as an output
}
else { //I want the output to be those in this else statement
do {
printf("Enter Name:\n");
fflush(stdin); //flushing the input
scanf("%s", name);
printf("Enter Student Number:");
scanf("%d", &ID);
fprintf(cfPtr, "%d %s\n", ID, name);
} while (ID != -1);
fclose(cfPtr);
}
return 0;
}
```
Output:
> File could not be opened...

#6: Post edited by

hkotsubo‭ · 2021-12-07T13:26:35Z (almost 3 years ago)
Better title, fix code block

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~~When I run this program, it gives me the output of the 'if statement', how can I access the 'else statement' for me to enter the student details?~~

Why does fopen return NULL?

~~````#include<stdio.h>~~
#include<stdlib.h>
int main (void){
FILE *cfPtr;
char name[15];
int ID;
if ((cfPtr = fopen("students.txt","w")) == NULL){
printf("File could not be opened...\n"); //program gives me this as an output
}
else { //I want the output to be those in this else statement
do {
printf("Enter Name:\n");
fflush(stdin); //flushing the input
scanf("%s", name);
printf("Enter Student Number:");
scanf("%d", &ID);
fprintf(cfPtr, "%d %s\n", ID, name);
} while (ID != -1);
fclose(cfPtr);
}
return 0;
}
~~Output: File could not be opened...~~
~~(I can't enter the student details)~~

````c
#include<stdio.h>
#include<stdlib.h>
int main (void){
FILE *cfPtr;
char name[15];
int ID;
if ((cfPtr = fopen("students.txt","w")) == NULL){
printf("File could not be opened...\n"); //program gives me this as an output
}
else { //I want the output to be those in this else statement
do {
printf("Enter Name:\n");
fflush(stdin); //flushing the input
scanf("%s", name);
printf("Enter Student Number:");
scanf("%d", &ID);
fprintf(cfPtr, "%d %s\n", ID, name);
} while (ID != -1);
fclose(cfPtr);
}
return 0;
}
```
Output:
> File could not be opened...

#5: Post edited by

Lundin‭ · 2021-12-07T11:10:45Z (almost 3 years ago)
More relevant tags

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c text fopen

c file-handling stdio fopen fopen

#4: Post edited by

dumplings‭ · 2021-12-07T10:59:46Z (almost 3 years ago)

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````#include<stdio.h>
#include<stdlib.h>
int main (void){
FILE *cfPtr;
char name[15];
int ID;
if ((cfPtr = fopen("students.txt","w")) == NULL){
printf("File could not be opened...\n"); //program gives me this as an output
}
else { //I want the output to be those in this else statement
do {
printf("Enter Name:\n");
fflush(stdin); //flushing the input
scanf("%s", name);
printf("Enter Student Number:");
scanf("%d", &ID);
fprintf(cfPtr, "%d %s\n", ID, name);
} while (ID == -1); //our stop
fclose(cfPtr);
}
return 0;
}
Output: File could not be opened...
(I can't enter the student details)

````#include<stdio.h>
#include<stdlib.h>
int main (void){
FILE *cfPtr;
char name[15];
int ID;
if ((cfPtr = fopen("students.txt","w")) == NULL){
printf("File could not be opened...\n"); //program gives me this as an output
}
else { //I want the output to be those in this else statement
do {
printf("Enter Name:\n");
fflush(stdin); //flushing the input
scanf("%s", name);
printf("Enter Student Number:");
scanf("%d", &ID);
fprintf(cfPtr, "%d %s\n", ID, name);
} while (ID != -1);
fclose(cfPtr);
}
return 0;
}
Output: File could not be opened...
(I can't enter the student details)

#3: Post edited by

dumplings‭ · 2021-12-07T10:57:59Z (almost 3 years ago)

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````#include<stdio.h>
#include<stdlib.h>
int main (void){
FILE *cfPtr;
char name[15];
int ID;
if ((cfPtr = fopen("students.txt","w")) == NULL){
printf("File could not be opened...\n"); //program gives me this as an output
}
else { //I want the output to be those in this else statement
do {
printf("Enter Name:\n");
fflush(stdin); //flushing the input
scanf("%s", name);
printf("Enter Student Number:");
scanf("%d", &ID);
fprintf(cfPtr, "%d %s\n", ID, name);
} while (ID == -1); //our stop
fclose(cfPtr);
}
return 0;
}
~~Output: File could not be opened...~~

````#include<stdio.h>
#include<stdlib.h>
int main (void){
FILE *cfPtr;
char name[15];
int ID;
if ((cfPtr = fopen("students.txt","w")) == NULL){
printf("File could not be opened...\n"); //program gives me this as an output
}
else { //I want the output to be those in this else statement
do {
printf("Enter Name:\n");
fflush(stdin); //flushing the input
scanf("%s", name);
printf("Enter Student Number:");
scanf("%d", &ID);
fprintf(cfPtr, "%d %s\n", ID, name);
} while (ID == -1); //our stop
fclose(cfPtr);
}
return 0;
}
Output: File could not be opened...
(I can't enter the student details)

#2: Post edited by

dumplings‭ · 2021-12-07T10:57:24Z (almost 3 years ago)

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````#include<stdio.h>
#include<stdlib.h>
int main (void){
FILE *cfPtr;
char name[15];
int ID;
if ((cfPtr = fopen("students.txt","w")) == NULL){
printf("File could not be opened...\n"); //program gives me this as an output
}
else { //I want the output to be those in this else statement
do {
printf("Enter Name:\n");
fflush(stdin); //flushing the input
scanf("%s", name);
printf("Enter Student Number:");
scanf("%d", &ID);
fprintf(cfPtr, "%d %s\n", ID, name);
} while (ID == -1); //our stop
fclose(cfPtr);
}
return 0;
}

````#include<stdio.h>
#include<stdlib.h>
int main (void){
FILE *cfPtr;
char name[15];
int ID;
if ((cfPtr = fopen("students.txt","w")) == NULL){
printf("File could not be opened...\n"); //program gives me this as an output
}
else { //I want the output to be those in this else statement
do {
printf("Enter Name:\n");
fflush(stdin); //flushing the input
scanf("%s", name);
printf("Enter Student Number:");
scanf("%d", &ID);
fprintf(cfPtr, "%d %s\n", ID, name);
} while (ID == -1); //our stop
fclose(cfPtr);
}
return 0;
}
Output: File could not be opened...

#1: Initial revision by

dumplings‭ · 2021-12-07T10:56:47Z (almost 3 years ago)

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When I run this program, it gives me the output of the 'if statement', how can I access the 'else statement' for me to enter the student details?

````#include<stdio.h>
#include<stdlib.h>
int main (void){
  
   FILE *cfPtr; 
   char name[15];
   int ID;
   if ((cfPtr = fopen("students.txt","w")) == NULL){
    printf("File could not be opened...\n"); //program gives me this as an output
   }
   else { //I want the output to be those in this else statement
        do {
            printf("Enter Name:\n"); 
            fflush(stdin); //flushing the input
            scanf("%s", name); 
            printf("Enter Student Number:");
            scanf("%d", &ID);

            fprintf(cfPtr, "%d %s\n", ID, name); 
        } while (ID == -1); //our stop

        fclose(cfPtr); 
   }
    return 0; 
}

c text fopen

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