fscanf() return value

[Cross]

Hello

I am using the following code to check fscanf() error value.
----------------------------------
#include <stdio.h>
int main(){
char arr[6];
int a;
FILE *fs=fopen("lessread.in", "r");
if(fs){
a = fscanf(fs, "%5s", arr);
printf("%s %d\n", arr, a);
}else{
fprintf(stderr, "read error.\n");
}
return 0;
}
-----------------------------------------

The contents of the file are:
---------------------------------
les
---------------------------------
The manual said that if end-of-file is reached before specified characters are
read, EOF is returned. However, my output is:
---------------------------------------
les 1
---------------------------------------

My actual motive: when I am using fscanf() to read a file with the format
sequence "%[^c]" where c is some character, how do I know whether EOF has been
reached or the read was successful.

Regards,
Cross

 

[Cross]

Hello

I am using the following code to check fscanf() error value.
----------------------------------
#include <stdio.h>
int main(){
char arr[6];
int a;
FILE *fs=fopen("lessread.in", "r");
if(fs){
a = fscanf(fs, "%5s", arr);
printf("%s %d\n", arr, a);
}else{
fprintf(stderr, "read error.\n");
}
return 0;
}
-----------------------------------------

The contents of the file are:
---------------------------------
les
---------------------------------
The manual said that if end-of-file is reached before specified characters are
read, EOF is returned. However, my output is:
---------------------------------------
les 1
---------------------------------------

My actual motive: when I am using fscanf() to read a file with the format
sequence "%[^c]" where c is some character, how do I know whether EOF has been
reached or the read was successful.

Regards,
Cross

Well I read that fscanf() shall return te number of successful conversions.
However, %5s should not count as a successful conversion when only 3 characters
are read. I also tried feof() after the fscanf(). It returns 0. Please explain.

 

[Moi]

Cross wrote:

a = fscanf(fs, "%5s", arr);
printf("%s %d\n", arr, a);

-----------------------------------------

The contents of the file are:
---------------------------------
les
---------------------------------
The manual said that if end-of-file is reached before specified
characters are read, EOF is returned. However, my output is:
--------------------------------------- les 1
---------------------------------------

My actual motive: when I am using fscanf() to read a file with the
format sequence "%[^c]" where c is some character, how do I know
whether EOF has been reached or the read was successful.

Regards,
Cross

Well I read that fscanf() shall return te number of successful
conversions. However, %5s should not count as a successful conversion
when only 3 characters are read. I also tried feof() after the fscanf().
It returns 0. Please explain.

"Number of successful conversions" := "number of %'s that have been
successfully matched" (and assignments made)

So it is *not* the number of _characters_, but the number of "items"

HTH,
AvK

 

[James Kuyper]

Hello

I am using the following code to check fscanf() error value.
----------------------------------
#include <stdio.h>
int main(){
char arr[6];
int a;
FILE *fs=fopen("lessread.in", "r");
if(fs){
a = fscanf(fs, "%5s", arr);
printf("%s %d\n", arr, a);
}else{
fprintf(stderr, "read error.\n");
}
return 0;
}

The 5 in "%5s" doesn't mean "read 5 non-whitespace characters, report an
error if there are less than 5". It means "read in no more than 5
non-whitespace characters".

 

[Cross]

The 5 in "%5s" doesn't mean "read 5 non-whitespace characters, report an
error if there are less than 5". It means "read in no more than 5
non-whitespace characters".

Thank you for the clarification.

 

[Barry Schwarz]

Hello

I am using the following code to check fscanf() error value.
----------------------------------
#include <stdio.h>
int main(){
char arr[6];
int a;
FILE *fs=fopen("lessread.in", "r");
if(fs){
a = fscanf(fs, "%5s", arr);
printf("%s %d\n", arr, a);
}else{
fprintf(stderr, "read error.\n");

This error message is misleading. The problem did not occur during
reading the file but during opening it.

}
return 0;
}
-----------------------------------------

The contents of the file are:
---------------------------------
les
---------------------------------
The manual said that if end-of-file is reached before specified characters are
read, EOF is returned. However, my output is:
---------------------------------------
les 1
---------------------------------------

My actual motive: when I am using fscanf() to read a file with the format
sequence "%[^c]" where c is some character, how do I know whether EOF has been
reached or the read was successful.

Regards,
Cross

 

[Cross]

This error message is misleading. The problem did not occur during
reading the file but during opening it.

Thanks. Will edit it.