K&R Error: conflicting method definition

Question

I am going through K&R (2 ed.) to learn C as I've been trying to get a basis in lower-level languages to help my programming and also because I want to know C. The book is absolutely fantastic; however, a program they provided on pp. 29 (Sec 1.9 Character Arrays) does not compile. This is the code

#include <stdio.h>
#define MAXLINE 1000    /* maximum input line size */

int getline(char line[], int maxline);
void copy(char to[], char from[]);

/* print longest input line */
main()
{
    int len;            /* current line length */
    int max;            /* maximum length seen so far */
    char line[MAXLINE];     /* current input line */
    char longest[MAXLINE];  /* longest line saved here */

    max = 0;
    while ((len = getline(line, MAXLINE)) > 0)
        if (len > max) {
            max = len;
            copy(longest, line);
        }
    if (max > 0)    /* there was a line */
        printf("%s", longest);
    return 0;
}

/* getline:  read a line int s, return length */
int getline(char s[], int lim)
{
    int c, i;

    for (i = 0; i<lim-1 && (c=getchar())!=EOF && c!='\n'; ++i)
        s[i] = c;
    if (c == '\n') {
        s[i] = c;
        ++i;
    }
    s[i] = '\0';
    return i;
}

/* copy:  copy 'from' into 'to'; assume to is big enough */
void copy(char to[], char from[])
{
    int i;

    i = 0;
    while ((to[i] = from[i]) != '\0')
        ++i;
}

When I run cc longest_line.c (that's what I called it) I get an error that getline has conflicting definitions as it was already defined in stdio.h. My question is, how do I resolve this/can I resolve this without giving getline a different name?

Answer 1

As @Olaf commented, getline() is standard POSIX,

K&R second edition is ansi 89 standard.

Just compile in ansi mode, to prevent the collision with POSIX libraries:

gcc -ansi source.c

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