copy string in c using pointer

Question

Code copy string in C

#include <stdio.h>
char *copyString(char *,char *);
void main()
{
    char *first = (char *)calloc(sizeof(char),10);
    char *second = (char *)calloc(sizeof(char),10);
    printf("Enter first string:\t");
    scanf("%s",first);
    printf("%s",copyString(first,second));
}
char *copyString(char *a,char *b)
{
    int i=0;
    while(*(a+i)!='\0')
    {
        *(b+i)=*(a+i);
        i++;
    }
    *(b+i)='\0';
    return b;
}

Case 1:

Input : Hello

Output : Hello

Case 2:

Input : Hello World

Output : Hello

So, my question is whether space is considered as newline/null ?? Because, in second case, it shows like this..

md5 · Accepted Answer · 2012-11-06 17:05:02Z

9

By default, scanf stops reading the standard input stream when a space character ' ' is encountered. To fix it, you can use a scanset.

scanf("%[^\n]", first);

answered Nov 6, 2012 at 17:05

md5

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3 Comments

Ravi Over a year ago

why so ?? space is also a character. isn't ??

Aniket Inge Over a year ago

yes that's how scanf() is defined. It will stop reading after first whitespace

Ravi Over a year ago

[^\n] what does it mean ?? i believe, this is used for checking pattern for new line. But, my question is instead of %s, we have used %[^\n] and it works. how ??

Aniket Inge · Accepted Answer · 2012-11-06 17:16:11Z

2

scanf() stops reading after the first whitespace by default. Use fgets() or gets()[unsafe]. With regards to why it is this way, you might want to read the POSIX pages here: http://www.unix.com/man-page/POSIX/3posix/scanf/ and ISO C standards here: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf. It has a lengthy description on how scanf() and fscanf()(and all other standard C functions) should work. These are generally followed guidelines on how functions in C library should work.

All compilers strive hard to create POSIX compliant standard-c libraries that work the same across most UNIX'ish platforms.

The standard C functions are actually defined here: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf

edited Nov 6, 2012 at 17:16

answered Nov 6, 2012 at 17:05

Aniket Inge

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Comments

P.P · Accepted Answer · 2012-11-06 17:06:31Z

1

It's because stops reading after whitespace when you input it the string. So you actaully only have "Hello" in your first string, not "Hello world".

Use fgets() to read the whole line.

answered Nov 6, 2012 at 17:06

P.P

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Comments

iabdalkader · Accepted Answer · 2012-11-06 17:06:48Z

1

As suggested scanf stops at the first whitespace, you could use fgets instead to read the whole line. And when you get that working allocate more space, because "Hello World" is 12 bytes not 10.

answered Nov 6, 2012 at 17:06

iabdalkader

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1 Comment

Ravi Over a year ago

sorry... that was just an example.. my main question was... it is not reading after space character

Abubakkar · Accepted Answer · 2012-11-06 17:08:12Z

0

Your scanf is scanning just one string for two strings to be scanned you should write:

      scanf("%s %s",first,second);

Similarly for more strings to be scanned you should do like this that is giving as many %s as many strings you want to scan.

answered Nov 6, 2012 at 17:08

Abubakkar

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Comments

rharrison33 · Accepted Answer · 2012-11-06 17:10:35Z

0

The scanf function here will read input until it encounters whitespace. You will need to implement a readline function.

answered Nov 6, 2012 at 17:10

rharrison33

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usman mehmood · Accepted Answer · 2012-11-06 17:12:59Z

0

use #include and utilize this function strcpy of string.h lib. following is the example:

    strcpy(first, second);

This should run fine.

answered Nov 6, 2012 at 17:12

usman mehmood

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