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-   -   last character of a string - in C (http://www.go4expert.com/forums/character-string-c-t8647/)

endfx 5Feb2008 07:19

last character of a string - in C
 
I'm trying to read 4 characters from a file, and then output them to the screen.
the file contains:
abcdefgh


This is my basic code:

char *filename = "file.txt";
char *line[5];

FILE *fp = fopen(filename, "r");
fread (line, sizeof(char), 4, fp);

line[4] = '\0';
printf("line: %s\n", line);

The output is abcdW

Why is the last character of my output always screwed up?
My goal is to (eventually) read in 50 characters, print to screen, then read in another
50 characters, etc.

I just can't figure out why the 5th character which is supposed to be null, gets printed
all scewed up.

Thanks!

oogabooga 5Feb2008 21:56

Re: last character of a string - in C
 
Quote:

Originally Posted by endfx
char *line[5];

You want char line[5] for an array of chars. You are declaring an array of pointers to chars then reading 4 bytes into the first pointer and storing zero in the last pointer then passing the address of the first pointer to printf (with %s) and it prints chars until it happens to find a zero.

Also, sizeof(char) is always 1 since the sizeof operator returns sizes in multiples of the size of a char (which I believe is supposed to represent the smallest addressable unit of memory on the machine, which on PCs is 1 8-bit byte).

fgets is more appropriate for reading chars.

P.S., remember to use a code block next time to properly display your code.


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