Reading from a file
I have a file with names:
Tammy
Jason
Carl
Thomas
Henry
I created a character array name
and then have this:
My problem is my output for some odd reason cuts off the T on Tammy. All the other names print to the console correctly.Code:while((currentCharacter = getc(fp)) != EOF) { fscanf(fp, "%s", name); printf("%s \n", name); }
How do i fix this?
Last edited by drater; 02-14-2008 at 10:21 PM.
((currentCharacter = getc(fp)) != EOF
What do you think this does?
Gets the current character as long as it isn't the end of the file.
Mhm, but you need to think of the consequences when it isn't the end of the file yet. Part of the data will be stored in the return value of getc(), including the T in Tommy and the whitespace that fscanf() puts back.
As you might have guessed, scanf only can only change the stream state while some conversion is valid. Since string conversion ends when whitespace is encountered, *scanf() functions will put stuff back into the stream for future reading. Print out the character like this in your loop and see it's effects on your file reading:
It's probably best to work with *one* input method.Code:printf("\"%c\"\n", currentCharacter);
It printed 'T' at the top with '' for every other line. How do i make sure that it doesn't keep storing my T?Code:printf("\"%c\"\n", currentCharacter);
Should I just "printf(%c\"\n", currentCharacter);" at the beginning of my loop? or is there a parameter i can put in my while loop to make sure it doesn't keep my T?
Now that you see that data is being stored where it shouldn't be, you can fix the problem by sticking to one input method. For instance, you could read a character at a time, or use fscanf()'s return value to control the loop as you read.
See, the neat thing about fscanf is that it returns EOF also when there is nothing to read.
I tried:
And my program crashed. What am i doing it wrong?Code:while((currentCharacter = fscanf(fp, "%s", name)) != EOF) // get next char from input file until we reach EOF
From the manual page.
My bad. But provided you understand what that says you should know what to do now. Just read until nothing is converted.Code:RETURN VALUES These functions return the number of input items assigned, which can be fewer than provided for, or even zero, in the event of a matching failure. Zero indicates that, while there was input available, no conversions were assigned; typically this is due to an invalid input character, such as an alphabetic character for a `%d' conversion. The value EOF is returned if an input failure occurs before any conversion such as an end-of-file occurs. If an error or end-of-file occurs after conversion has begun, the num- ber of conversions which were successfully completed is returned.
This looks like
while ( (currentCharacter = fscanf( /** ... **/ ) ) == 1 )
currentCharacter now contains the sum of successful conversions.
Last edited by whiteflags; 02-14-2008 at 11:56 PM.
Thank you, citizen, for helping me with my original problem.
I am supposed to tab if the name is more than 6 characters, and I know how to look for exactly 6 characters:but how do i do x > 6 length?Code:if ((int)cityName[6])
I'm not fully understand what you are trying to do, but strlen will return you number of characters in the null-terminated stringOriginally Posted by drater
so strlen(cityName) will give the number of chars in the cityName if it is null-terminated.
PS. Bytheway if ((int)cityName[6]) - (int) here gives nothing to correctness of the code and makes it less readable
All problems in computer science can be solved by another level of indirection,
except for the problem of too many layers of indirection.
– David J. Wheeler
If you want to use fscanf, you had better read this.
Code:do { fscanf(fp, "%s", name); printf("%s \n", name); }while((currentCharacter = getc(fp)) != EOF);
I think this will work for you.
And so you post the same poor use of fscanf even though I just posted a link about it.
Read people!
