Program that shows biggest line...

[i_can_do_this]

this program counts lines and prints out the longest line from input.

#include <stdio.h>

#define MAXLINE 1000

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

int main()
{
    int len;
    int max;
    char line[MAXLINE];
    char longest[MAXLINE];
    
    max = 0;
    while ((len = getline(line, MAXLINE)) > 0)
        if(len > max) {
            max = len;
            copy(longest, line);
           }
     if(max > 0)
        printf("%s", longest);
     return 0;
}

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;
}

void copy(char to[], char from[])
{
    int i;
    
    i = 0;
    while((to[i] = from[i]) != '\0')
        ++i;
}

ok im reading the c programming language 2nd edition ever since i started, everything from the beginning until now i was able to understand.
i dont get alot of things in this program so i will be asking tons of questions about this...

1. the book doesnt explain '\0' very clear about how it works in this program, only to what it does... can someone explain to me the purpose of it here?

2.The "if" statement in getline has the same statement body as the for loop so what was the point of that??

3. How does copy function in main if it doesnt return anything??

4. in the for loop in getline, why is it"i < lim -1" and not i<lim? doesnt lim already represents max?

sorry and can u please give me a simple explanation of the entire program too?... those questions were things i dont understand but a clear explanation of the entire program would help me even further. thanks...

[Maragato]

1. the book doesnt explain '\0' very clear about how it works in this program, only to what it does... can someone explain to me the purpose of it here?

2.The "if" statement in getline has the same statement body as the for loop so what was the point of that??

3. How does copy function in main if it doesnt return anything??

4. in the for loop in getline, why is it"i < lim -1" and not i<lim? doesnt lim already represents max?

sorry and can u please give me a simple explanation of the entire program too?... those questions were things i dont understand but a clear explanation of the entire program would help me even further. thanks...

Assuming you have the second edition.
1. section 5.5 page 104
4. refer to question 1
2. it is explained in the page before.
3. you miss the concept of a pointer refer to the beginning of the chapter.

[Richie T]

[EDIT]
Beaten by Maragato, but if the book does not explain well enough, perhaps the
following will.
[/EDIT]

Ok here goes:

1. In C, a string is a concept, and while it is physically just an array of
characters, in order to use special string processing functions such as strcmp
(used for comparing strings for equality), there needs to be some standard way
to determine where the string ends (since the string is not necessarily filling
the array it is stored in). Thats why we have \0' - its just a standard way of
saying "this is the end of the string - anything after this does not matter".
That's why the program is using '\0' - to make them standard C strings.

2. I assume you mean this:

if(c == '\n'){
s[i] = c;
++i;
}

well if you read the code carefully, you will see that the for loop is only executing
one statement, and the for loop will end if a user presses enter ('\n'), or EOF.
In the event that the user pressed enter to break the loop, the if statement
entered above will cause the '\n' to be stored in the string, which would not
happen with the current structure of the for loop. We would not want to store
the EOF in the string since we want a string of 0 length. Basically, this statement
is designed to cover the possibility that the user enters less than the specified
number of characters, to ensure that the '\n' is also stored - its not necessary,
it's just a design choice. The function fgets exhibits the same behavior.

3. Arrays are always passed by reference, something you may not have covered
yet if you're asking. Look up pointers. Basically, when passing an array to a
function, any modiications made to the array inside the function modify the
array originally passed (different to normally passing an int to the function,
where the function receives a copy of the data, not the original data).

4. Since we need to have the '\0' character to make it a string, we need to leave
space. Lets say that lim is 10. That means our array char hold 10 characters,
(from array indices 0 to 9). But if we need to always have a '\0', then we are
always using one character - so we can really only read in a maximum of 9
data characters (array indices 0 to 8), then a '\0'.


[ALSO]

If you understand those answers, you pretty much have the program itself
down, so I'll just summarise what it does:

1. Program enters a loop.
2. User is prompted to enter some text.
3. If the text entered is longer than the last longest value saved in the
longest array, overwrite it using the copy function, otherwise don't.
4. If the user enters no characters (By signalling EOF to the program), end the
loop.
5. Print out the string stored in the longest array.

[/ALSO]

[whiteflags]

> Arrays are always passed by reference pointer ...

We don't want to breed confusion about references and how they aren't really in C.

[Maragato]

> Arrays are always passed by reference pointer ...

We don't want to breed confusion about references and how they aren't really in C.

IS this accurate?
http://www.c-faq.com/ptrs/passbyref.html

[itsme86]

Yes. I've never seen anything inaccurate on c-faq.com, and that particular entry is no exception.

[Richie T]

Sorry if my statement caused confusion, I suppose not everyone knows that the
term "pass-by-reference" with regard to C means pointers are involved. I have
never had confusion about that terminology when used in C but I understand
how it could be misleading since the most accurate term is pass-by-pointer.