CODEWITHSUNDEEP
c
user8267426
user8267426

Reputation:

fread. fseek. ftell. " warning: value computed is not used "

how to instead of

char text[10000];

do

char text[fp_len];

i also get this warning:

warning: value computed is not used

FILE *fp;
fp = fopen(path, "r");
int fp_len;
fseek(fp, 0, SEEK_END)+1;
fp_len = ftell(fp); 
fseek(fp, 0, SEEK_SET);
printf("%d---", fp_len);

char text[10000];
fread(text, fp_len, 1, fp);

printf("%s", text);

should i also add: 

text[]= '\0'

to the bottom. ( above printf )

Upvotes: 1

Views: 204

Answers (2)

Jean-François Fabre
Jean-François Fabre

Reputation: 140287

as noted in comments fseek(fp, 0, SEEK_END)+1 is just adding the return code of fseek to 1 (why would you do that?), and the result (useless) is dropped.

Now, you could create a variable length array (perfectly legal in C) using char text[fp_len];, that would work, but generally auto variable space is not designed to be big, so you can have "stack overflow" if the file is too big: in that case char *text = malloc(fp_len) is preferred.

If you want to null-terminate it (which is useful only if you want to printf the contents of the file, and if the file contains text), don't forget to add 1 to your buffer so you can legally do text[fp_len] = '\0';

Aside: fseek(fp, 0, SEEK_SET); could be just rewind(fp);

Upvotes: 1

unalignedmemoryaccess
unalignedmemoryaccess

Reputation: 7441

You get warning of unused value because when you add +1 to returned value, you are doing nothing

fseek(fp, 0, SEEK_END)+1;

is evaluated to

fseek(fp, 0, SEEK_END);

But compiler warns you about, maybe you forgot to assign result somewhere.

To read data, reserve memory in HEAP region using dynamic allocation otherwise you may enter to stack overflow if your fp_len is too big.

char *text = malloc(sizeof(*text) * (fp_len + 1));

And don't forget to include stdlib.h

Upvotes: 1

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