warning: passing argument 1 of 'fgets' from incompatible pointer type

This is a discussion on warning: passing argument 1 of 'fgets' from incompatible pointer type within the C Programming forums, part of the General Programming Boards category; When I try and compile a simple c program, I get an error warning: passing argument 1 of 'fgets' from ...

  1. #1
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    warning: passing argument 1 of 'fgets' from incompatible pointer type

    When I try and compile a simple c program, I get an error

    warning: passing argument 1 of 'fgets' from incompatible pointer type

    I am compiling with gcc. What am I doing wrong?

    Code:
    #include <string.h>
    #include <stdio.h>
    #define MAX_CHAR 132
    #define MAX_SIZE 65536
    FILE *file;
    
    int main(void)
    {
            file = fopen("words", "r");
            char ch;
            char string[MAX_CHAR];
            char temp[MAX_CHAR];
            char words[MAX_SIZE][MAX_CHAR];
            register int counter = 0, number = 0, a = 0;
            srand(time(NULL));
            while ( fgets(&string, MAX_CHAR+1, file) != NULL )
            {
                    a=0;
                    while ( string[a++] != '\n' );
                    string[a-1] = 0;
                    strcpy(words[counter++], string);
            }
    
            number = rand() % counter;
            strcpy(string, words[number]);
    
            while (strcmp(temp,string) != 0)
            {
                    printf("Enter a character: " );
                    ch = getc(stdin);
                    a=0;
                    while ( string[a] != 0 )
                    {
                            if ( string[a] == ch )
                                    temp[a] = ch;
                            else
                            {
                                    if ( temp[a] == 0 || temp[a] == ' ' ) 
                                            temp[a] = ' ';
                            }
                            a++;
                    }
                    printf("%s\n", temp);
            }
    return 0;
    }

  2. #2
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    I see, I need to take the & away before the string. I need the var name not the address of the var.

  3. #3
    Registered User hk_mp5kpdw's Avatar
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    The var name used in this context is the address. BTW,
    Code:
    #define MAX_CHAR 132
    
    char string[MAX_CHAR];
    
    while ( fgets(string, MAX_CHAR+1, file) != NULL )
    ...this should not be +1.
    "Owners of dogs will have noticed that, if you provide them with food and water and shelter and affection, they will think you are god. Whereas owners of cats are compelled to realize that, if you provide them with food and water and shelter and affection, they draw the conclusion that they are gods."
    -Christopher Hitchens

  4. #4
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    thanks, I'll fix that too.

  5. #5
    Banned master5001's Avatar
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    Quote Originally Posted by sillyman View Post
    When I try and compile a simple c program, I get an error

    warning: passing argument 1 of 'fgets' from incompatible pointer type

    I am compiling with gcc. What am I doing wrong?

    Code:
    #include <string.h>
    #include <stdio.h>
    #define MAX_CHAR 132
    #define MAX_SIZE 65536
    FILE *file;
    
    int main(void)
    {
            file = fopen("words", "r");
            char ch;
            char string[MAX_CHAR];
            char temp[MAX_CHAR];
            char words[MAX_SIZE][MAX_CHAR];
            register int counter = 0, number = 0, a = 0;
            srand(time(NULL));
            while ( fgets(&string, MAX_CHAR+1, file) != NULL )
            {
                    a=0;
                    while ( string[a++] != '\n' );
                    string[a-1] = 0;
                    strcpy(words[counter++], string);
            }
    
            number = rand() % counter;
            strcpy(string, words[number]);
    
            while (strcmp(temp,string) != 0)
            {
                    printf("Enter a character: " );
                    ch = getc(stdin);
                    a=0;
                    while ( string[a] != 0 )
                    {
                            if ( string[a] == ch )
                                    temp[a] = ch;
                            else
                            {
                                    if ( temp[a] == 0 || temp[a] == ' ' ) 
                                            temp[a] = ' ';
                            }
                            a++;
                    }
                    printf("%s\n", temp);
            }
    return 0;
    }
    The & takes the address of the variable. Since string is a char [], then taking its address makes it a char *[] which is an invalid type of pointer (just as the error suggests). Drop the & and the +1. I also recommend naming your variable something else too since string is not a portable name (in C++ its actually a type).

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