spaces in char array in c

Question

how add space between two words in array ,i receive two words from the user his first name ,his last name what i need it to store the two arrays in one array between them a space

here is my code

#include <stdio.h>
int main()
{
    char first_name[15], last_name[15] ,full_name[32];
    int i=0,i2,first_name_length,last_name_length;
    printf("enter your first name\n");
    first_name_length = scanf("%s",first_name);
    printf("enter your last name\n");
    last_name_length = scanf("%s",last_name);
    for(i2 = 0;i2 < first_name_length;i2++){
        full_name[i] = first_name[i2];
        i++;
    }
    full_name[i++]=' ';
    for(i2 = 0;i2 < last_name_length;i2++){
        full_name[i] = last_name[i2];
        i++;
    }
    printf("%s",full_name);
    return 0;
}

the output when enter the "name" value in the both scanf :

n n

and it should be :

name name

edit:

#include <stdio.h>
int main()
{
    char first_name[15], last_name[15] ,full_name[32];
    int i=0,i2;
    printf("enter your first name\n");
    scanf("%14s",first_name);
    printf("enter your last name\n");
    scanf("%14s",last_name);
    for(i2 = 0;first_name[i2];i2++){
        full_name[i] = first_name[i2];
        i++;
    }
    full_name[i++]=' ';
    for(i2 = 0;last_name[i2];i2++){
        full_name[i] = last_name[i2];
        i++;
    }
    printf("%s",full_name);
    return 0;
}

the output when enter the "tom" value in the first scanf and "fox" value in the second scanf :

tom fox↓@

and it should be :

tom fox

Your first_name and last_name are 15 char each and full_name is 30. If you add a space between a max length first_name and max length last_name, you're going to be in trouble. — adamdc78
– adamdc78, Commented Feb 26, 2015 at 19:08
i edited my question what's now it doesn't work too it output only the first name but the last name not shown — tom fox
– tom fox, Commented Feb 26, 2015 at 19:10
You're not incrementing i after you set the space, you're incrementing it before hand. — adamdc78
– adamdc78, Commented Feb 26, 2015 at 19:11
i edited my question but it still output only the first name but the last name not shown — tom fox
– tom fox, Commented Feb 26, 2015 at 19:12
@tom fox Not good to update your post in the fashion you did. Recommend reverting to the previous version and appending new code, data or insights. — chux
– chux, Commented Feb 26, 2015 at 19:48

chux · Accepted Answer · 2015-02-26 19:55:40Z

4

The return value from scanf() is the number of fields successfully scanned, not the length of some string.

Use:

if (1 != scanf("%14s",first_name)) Handle_EOF_orNoInput();
first_name_length = strlen(first_name);`

Same for last_name

[Edit]

Since OP wants to not introduce new functions (like even strlen()), use "%n to find the length. "%n record the parsing position.

if (1 != scanf("%14s%n",first_name, &first_name_length)) Handle_EOF_orNoInput();

OR find length the hard way

if (1 != scanf("%14s",first_name)) Handle_EOF_orNoInput();
for (first_name_length = 0; first_name[first_name_length]; first_name_length++);

[Edit 2]

OP's latest does not terminate the string.

full_name[i] = '\0';  // add this
printf("%s",full_name);

edited Feb 26, 2015 at 19:55

answered Feb 26, 2015 at 19:35

chux

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16 Comments

tom fox Over a year ago

sorry i can't use any other functions expect the written in the code

Dima Maligin Over a year ago

@tomfox This is a great answer, you can iterate through first_name and look for '/0' instead of strlen.

chux Over a year ago

@Dima Maligin Just put that in.

tom fox Over a year ago

i updated the code to simple way but the problem is in the unknown chars

chux Over a year ago

The problem with your update is that you did not terminate the string. add full_name[i] = 0; before print.

|

Joël Hecht · Accepted Answer · 2015-02-26 19:55:37Z

1

Rewritten without the sprintf function and without pointers

#include <stdio.h>
int main()
{
    char first_name[15], last_name[15] ,full_name[32];
    int src, dest;
    printf("enter your first name\n");
    scanf("%s",first_name);
    printf("enter your last name\n");
    scanf("%s",last_name);

    dest = 0;
    src = 0;
    while (first_name[src] != 0) full_name[dest++] = first_name[src++];
    full_name[dest++] = ' ';
    src = 0;
    while (last_name[src] != 0) full_name[dest++] = last_name[src++];
    full_name[dest] = 0
    printf("%s",full_name);
    return 0;
}

edited Feb 26, 2015 at 19:55

answered Feb 26, 2015 at 19:31

Joël Hecht

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2 Comments

tom fox Over a year ago

sorry i can't use any other functions expect the written in the code

tom fox Over a year ago

i can't use the * before the variables

adamdc78 · Accepted Answer · 2015-02-26 19:43:30Z

0

Change

i++;
full_name[i]=' ';

to

full_name[i++]=' ';

Your for loop conditions are also not quite right:

for(i2 = 0;i2 < first_name_length;i2++){

edited Feb 26, 2015 at 19:43

answered Feb 26, 2015 at 19:12

adamdc78

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5 Comments

tom fox Over a year ago

it out put some unknown characters in the end of the name

tom fox Over a year ago

it loops until the chars of the array are finished what's the problem here i didn't type first_name_length any where in the code

adamdc78 Over a year ago

Can you update with your code changes and the output you're getting?

adamdc78 Over a year ago

Looks like I should have checked a better source for the return value of scanf().

tom fox Over a year ago

i updated the code to simple way but the problem is in the unknown chars

jschultz410 · Accepted Answer · 2015-02-26 19:51:57Z

0

The function scanf() does not return the number of characters read in. Rather, it returns the number of successful matches it read in (or error). In your runs, scanf() is returning 1, so you only copy the first character from first and last name to full name.

Also, you need to initialize full_name to all zeroes or nul terminate it after you are done copying the last name.

Furthermore, the way you are reading in the strings is dangerous. You should restrict how many characters the scanf() can read in, otherwise it will overflow your buffers and trash your memory (or let a hacker in, etc.):

if (1 != scanf("%14s", first_name))
  ; // TODO: handle unexpected input, EOF, error, etc.

Or even better:

#define STR(x) #x
#define SSTR(x) STR(x)
#define STR_FMT(x) "%" SSTR(x) "s"
#define FIRST_NAME_MAX_LEN 14

...

char first_name[FIRST_NAME_MAX_LEN + 1] = { 0 };

...

if (1 != scanf(STR_FMT(FIRST_NAME_MAX_LEN), first_name))
  ;  // TODO: handle unexpected input, EOF, error, etc.

edited Feb 26, 2015 at 19:51

answered Feb 26, 2015 at 19:40

jschultz410

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2 Comments

tom fox Over a year ago

for some reason i can't use define

jschultz410 Over a year ago

@tomfox Umm, ok, then just hardcode the constants even though that's typically bad form.

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