no output for the program even when it compiles

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3.00/5 (1 vote)

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I wrote the following program and compiled it using wxDev C++ 7.3.0.6 on windows 7, but I did not get the desired output(to print the longest line entered) even though it compiles without a hitch.

C++

#include <stdio.h>
#define MAXLINE 1000

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


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;
}

Please help me out?

Posted 28-Oct-11 5:15am

kr_harsha

Updated 28-Oct-11 5:44am

v4

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Sergey Alexandrovich Kryukov 28-Oct-11 11:40am

Why do you thing that successful compilation should mean any desired results during run-time? :-)
And what's "desired output"?
--SA

3 solutions

Solution 1

You did not specify what goes wrong, but my guess it that the program never stops and prints the longest string entered.

You set the program to stop reading lines when getline returns 0, however if you look at your getline you will see that it always stores the enter in it. This means that for an empty string the length is 1 and not 0.
So if you replace

C++

while( (len=getline(line, MAXLINE))>0)

with

C++

while( (len=getline(line, MAXLINE))>1)

you should get your expected result.

Posted 28-Oct-11 5:39am

André Kraak

Comments

kr_harsha 28-Oct-11 11:46am

the program does not give any output.
i entered this on the screen-

hey<enter>
kumar<enter>
^Z<ctrl+z>

after this the window closes...
no output at all..

Sergey Alexandrovich Kryukov 28-Oct-11 11:59am

Not true. It does output. Please see my solution, I explained what you can do.

André solution gets my 5 -- this is another variant of the same thing.
Just output some prompt before every call to getline.
--SA

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Sergey Alexandrovich Kryukov · Accepted Answer · 2011-10-28T05:45:00

Solution 2

It does output something. Did you expect some more?

The only call which outputs anything is printf at the end. You could easily fail to notice it, because this the application exists immediately after it.

Another problem: getline always return length > 0, even if one just presses Enter. I think you wanted to exit the loop if the user presses Enter; right now the loop executes infinitely unless the user end it with Ctrl+C, but then the result of the program is not output. Perhaps, return i − 1 instead of i, in this way, the length will be the string length not counting ending '\n' and '\0', which will be just fine for your purposes.

Well, and output prompt for the user before every call to getline; and you will be all right.

—SA

Posted 28-Oct-11 5:45am

Sergey Alexandrovich Kryukov

Updated 28-Oct-11 6:25am

v4

Comments

Andrew Brock 28-Oct-11 12:00pm

Almost.
"return i − 1 instead of i − 1", think you meant just "i" on that last one.
Also, it isn't the '\0' that it is counting in getline(), it is the '\n' that it is adding on.

Sergey Alexandrovich Kryukov 28-Oct-11 12:22pm

Whatever... thanks for correcting me anyway...
First text mistake was fixed, will fix another one...
--SA

kr_harsha 28-Oct-11 12:02pm

i tried i-1; still doen't give any output...

Sergey Alexandrovich Kryukov 28-Oct-11 12:25pm

Please, do yourself a favor, read again, this time thoroughly: 1) there is output at the end already; 2) no more output for you until you add some; I already advised you to do so and explained where.

Good luck, call again.
--SA

Andrew Brock · Accepted Answer · 2011-10-28T06:00:00

add #include <windows.h>, so we can use pause

in main:

C++

if(max>0)
        printf("%s\n", longest); //Add a \n in here
   system("PAUSE"); //This will allow you yo see the results before closing the window on you. Credit to SA for picking up on this

and a revised getline():

C++

int getline(char s[], int lim)
{
    int c, i;
 
    for(i=0; i < lim-1 && (c=getchar())!= EOF && c!='\n'; ++i)
        s[i]=c;
    //comment out this
    /*if(c=='\n')
    {
        s[i]=c;
        ++i;
    }*/
 
    s[i]='\0';
 
    return i;
}

This will allow you to enter a series of words, when you enter a blank word (just hit enter) it will break and print the longest work you entered.

no output for the program even when it compiles

3 solutions

Solution 1

Solution 2

Solution 3

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