possible use of atoi()

[_jamie]

Hey all! Spend 3 months since October reading my 700 page book for the second time, now I am on the second to last question before I finish it,...would like to finish the last exercise which includes writing a complete program. Would like to inventory my groceries I have in the freezer, refrigerator, and also in the dry stock shelf.

Just a quick question on this code:

// commandargs.c--Accessing command-line arguments.

#include <stdio.h>
#include <errno.h>

int file_copy( char *oldname, char *newname );

int main(int argc, char *argv[])
{
    int a, b;
    int count;
    char source[80], destination[80];

    /* Get the source and destination names. */

    if (argc < 2 || argc > 3)
    {
        printf("Enter 2 arguments only\n");
    }

    a = atoi(argv[1]);
    b = atoi(argv[2]);

    if( file_copy( a, b ) == 0 )
        puts("Copy operation successful");
    else
        fprintf(stderr, "Error during copy operation");
    return 0;
}

int file_copy( char *oldname, char *newname )
{
    FILE *fold, *fnew;
    int c;
    
    /* Open the source file for reading in binary mode. */

    if ( ( fold = fopen( oldname, "rb" ) ) == NULL )
        return -1;

    /* Open the destination file for writing in binary mode. */

    if ( ( fnew = fopen( newname, "wb" ) ) == NULL )
    {
        fclose ( fold );
        return -1;
    }

    /* Read one byte at a time from the source; if end of file */
    /* has not been reached, write the byte to the */
    /* destination. */

    while (1)
    {
        c = fgetc( fold );

        if (!feof( fold ) )
            fputc( c, fnew );
        else
            break;
    }

    fclose ( fnew );
    fclose ( fold );

    return 0;
}

Here..

    a = atoi(argv[1]);
    b = atoi(argv[2]);

Compiler is complaing about using atoi() in C99, not even sure if this is the right function, and was also wondering if strtol() would be.

Also...

[jamie@bindfix Lesson_22]$ cc -o ex_5_2 ex_5_2.c
ex_5_2.c:21:6: warning: implicit declaration of function 'atoi' is invalid in C99 [-Wimplicit-function-declaration]
        a = atoi(argv[1]);
            ^
ex_5_2.c:24:17: warning: incompatible integer to pointer conversion passing 'int' to parameter of type 'char *' [-Wint-conversion]
        if( file_copy( a, b ) == 0 )
                       ^
ex_5_2.c:6:22: note: passing argument to parameter 'oldname' here
int file_copy( char *oldname, char *newname );
                     ^
ex_5_2.c:24:20: warning: incompatible integer to pointer conversion passing 'int' to parameter of type 'char *' [-Wint-conversion]
        if( file_copy( a, b ) == 0 )
                          ^
ex_5_2.c:6:37: note: passing argument to parameter 'newname' here
int file_copy( char *oldname, char *newname );
                                    ^
3 warnings generated.

[laserlight]

When you see "implicit declaration of function", check that you have included the necessary headers or forward declared the function. In this case, you need to #include <stdlib.h>