I am failed to use stren with a pointer

Question

The program below describes: read everything in library.txt then put it in a level 2 char pointer, choose ramdomly a word from the pointer then use strlen to print a number of characters in that word. The problem is every number of characters are increase by 2 units. Examples:

helloworld (10 letters) -> 12 letters

abcdef (6 letters) -> 8 letters

uiop (4 letters) -> 6 letters

SUB-QUESTION: can anyone show me the way to return a char pointer from a function? I tried to do like this " char *read (FILE *library) " but on the Internet, they told me not to do that, so i did like the function below =)). please help.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int read (FILE *library){

    // count number of word in library.txt
    int n=0;
    char *s=(char *)malloc(256*sizeof(char));
    library=fopen("C:\\Users\\pc\\Desktop\\library.txt","rb");
    while (fgets(s, 256, library)!=NULL)
    {
        n++;
    }
    free(s);

    rewind(library);

    // put all words in library.txt to the level 2 pointer
    char **word=(char**)malloc(n*sizeof(char *));
    for (int i = 0; i < n; i++)
    {
        *(word+i)=(char *)malloc(256*sizeof(char));
        fgets(*(word+i), 256, library);
    }
    fclose(library);

    // choose a rondom word then return it to function
    int j=0;
    srand((int) time(0));
    j=rand()%n;
    return (int)*(word+j);
}

int main(){

    FILE *library;

    int length_word=0;
    length_word=strlen(read(library));
    printf("%s%d",read(library),length_word);

    return 0;
}

Answer 1

For starters the function declaration

int read (FILE *library)

does not make sense because within the function the parameter is overwritten, that is its value is not used.

And instead of the pointer of the type char * the function returns an object of the type int.

Also it is unclear why you are opening the file in the binary mode instead of the text mode.

library=fopen("C:\\Users\\pc\\Desktop\\library.txt","rb");
                                                    ^^^^

Secondly, this return statement

return (int)*(word+j);

does not make sense and results in a memory leak because all allocated memory except the memory pointed to by the the pointer *( word+j ) is not freed.

So before exiting from the function you have to free the allocated memory.

For example

char *p = *( word + j );
for ( int i = 0; i < n; i++ )
{
    if ( i != j ) free( *( word + i ) );
}

free( word );

return p;

Correspondingly the function shall have the return type char *.

In main you two times call the function. And again does not free the memory pointed to by the returned pointer.

length_word=strlen(read(library)); printf("%s%d",read(library),length_word)

Also pay attention to the the function fgets can append the new line character '\n' to the input string. You need to remove it.

It can be done the following way

for (int i = 0; i < n; i++)
{
    *(word+i)=(char *)malloc(256*sizeof(char));
    fgets(*(word+i), 256, library);
    word[i][ strcspn( word[i], "\n" ) ] = '\0';
}

if you are using an old compiler that does not convert carriage return escape character and the new line escape character to the one new line escape character then you can write

    word[i][ strcspn( word[i], "\r\n" ) ] = '\0';

Thus the function should be declared like

char * read( void );

within the function you should declare

FILE *library;

in the function main you should write

char *word = read();

and then

size_t length_word = strlen( word );
printf("%s%zu", word,length_word) ;
free( word );