conflicting types for the sample from The C Programming Language 1.9

Question

I'm new to C and I'm using The C Programming Language, I copied down 1.9 which tries to print the longest line. While I try to build the program in Xcode, it shows there are errors of conflicting types and a problem with expression, I've tried to put the function "getline" before the main but I still don't know what is going wrong.

#include <stdio.h>
#define MAXLINE 1000 /* maximum input line size */
int getline(char line[ ], int marline);     ----ISSUE:Conflicting types for "getline"
void copy(char to[ ], char from[ ]);

/* print longest input line*/
int 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)     ------ISSUE:Expected Expression
    if (len>max){
        max=len;
        copy(longest, line); }
if (max>0) /* there was a line*/
    printf("%s", longest);
return 0;}

/* getline: read a line into s, return length */
int getline(char s[ ], int lim){            ----ISSUE:Conflicting types for "getline"    
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;}

getline is reserved function. Rename that function, eg: my_getline — LPs
while ((len=getline(line[ ], MAXLINE))>0) -> while ((len=getline(line, MAXLINE))>0). For the rest, see answer below. — Jabberwocky
int main(){ tends to be frowned upon. Use int main ( void ) or int main(int argc, char **argv) instead — Elias Van Ootegem

unwind unwind · Accepted Answer · 2016-10-11T09:07:33

It's conflicting with the standard librarys's getline() function, which didn't exist when that book was written (it's from POSIX.1-2008, the book is ... older).

Rename the function in the example, to avoid the collision. Just use mygetline() instead and you should be fine.

conflicting types for the sample from The C Programming Language 1.9

2 Answers