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Hi everyone!
I'm new at C and I need your help. How do I can input string in string pointer and then show it on terminal?
I tried to do this:
but seems like it's incorrect. Please, help!Code:#include <stdio.h>
#include <string.h>
#define eof '\n'
main()
{
char c, *City1;
malloc();
printf("Please enter first city: ");
while((City1=getchar()) != eof);
}
malloc() returns a pointer to a place in memory reserved for as many bytes as you want. Your compiler should have complained about your use of malloc(). Also, getchar() returns an integer so your compiler should have complained about that too.
Also, '\n' doesn't represent eof. '\n' represents eol (end of line -- new line to be more precise.)
Code:#include <stdio.h>
#include <stdlib.h> // For malloc()
int main(void)
{
int c;
char *City1, *ptr;
City1 = malloc(100); // Allocate 100 bytes and make City1 point to reserved memory
if(City1 == NULL)
{
puts("Memory allocation failed!");
return 1;
}
ptr = City1; // Make ptr point to the beginning of the reserved memory
while((c = getchar()) != '\n' && c != EOF) // EOF is a real macro indicating the input stream ended
{
*ptr = c; // Set the memory pointed to by ptr equal the character that was input
ptr++;
}
*ptr = '\0'; // Terminate the string
puts(City1); // Print out the string
free(City1); // Free the reserved memory
return 0;
}
Only because it is, and you know it. Did you just slap together random crap?Quote:
Originally Posted by BLooDCorpse
itsme86 was nice enough to write out an example for you, but I wouldn't bank on that for the future.
itsme86, thanks! Now I'll raise it to 10 cities and add the sort. Hope I can do it myself. =)
MacGyver, programming for me is very hard work. I started to learn programming about 5 years ago and all this time I know, that programming is not for me, but I've to do some labs for th Institute.
Five years and here we are.... oh joy.
Well, I hope everything works out the way it should.
I started to learn C two months ago ;) And I hate pointers =)Quote:
Originally Posted by MacGyver
Can you tell, why when I compare two pointers and then exchange them, their data is lost?
Code:c=1;
while(c)
{
c=0;
if(strcmp(City1, City2) > 0)
{
c=1;
strcpy(City1, ptr);
strcpy(City2, City1);
strcpy(ptr, City2);
}
}
I've fixed this problem by doing this
Code:c=1;
while(c)
{
c=0;
if(strcmp(City1, City2) > 0)
{
c=1;
*ptr=*City1;
*City1=*City2;
*City2=*ptr;
*ptr='\0'
}
}
Now my program works perfectly with digits, but if I enter at least 1 word, it start to think and it never ends. What might it be?
Code:#include <stdio.h>
#include <stdlib.h> // For malloc()
int main(void)
{
int c;
char *City1, *City2, *City3, *City4, *City5, *City6;
char *City7, *City8, *City9, *City10, *ptr;
City1 = malloc(100); // Allocate 100 bytes and make City1 point to reserved memory
City2 = malloc(100);
City3 = malloc(100);
City4 = malloc(100);
City5 = malloc(100);
City6 = malloc(100);
City7 = malloc(100);
City8 = malloc(100);
City9 = malloc(100);
City10 = malloc(100);
ptr = City1; // Make ptr point to the beginning of the reserved memory
printf("Please enter first city: ");
while((c = getchar()) != '\n' && c != EOF) // EOF is a real macro indicating the input stream ended
{
*ptr = c; // Set the memory pointed to by ptr equal the character that was input
ptr++;
}
*ptr = '\0';
ptr = City2;
printf("Please enter second city: ");
while((c = getchar()) != '\n' && c != EOF)
{
*ptr = c;
ptr++;
}
*ptr = '\0';
ptr = City3;
printf("Please enter third city: ");
while((c = getchar()) != '\n' && c != EOF)
{
*ptr = c;
ptr++;
}
*ptr = '\0';
ptr = City4;
printf("Please enter forth city: ");
while((c = getchar()) != '\n' && c != EOF)
{
*ptr = c;
ptr++;
}
*ptr = '\0';
ptr = City5;
printf("Please enter fifth city: ");
while((c = getchar()) != '\n' && c != EOF)
{
*ptr = c;
ptr++;
}
*ptr = '\0';
ptr = City6;
printf("Please enter sixth city: ");
while((c = getchar()) != '\n' && c != EOF)
{
*ptr = c;
ptr++;
}
*ptr = '\0';
ptr = City7;
printf("Please enter seventh city: ");
while((c = getchar()) != '\n' && c != EOF)
{
*ptr = c;
ptr++;
}
*ptr = '\0';
ptr = City8;
printf("Please enter eight city: ");
while((c = getchar()) != '\n' && c != EOF)
{
*ptr = c;
ptr++;
}
*ptr = '\0';
ptr = City9;
printf("Please enter nineth city: ");
while((c = getchar()) != '\n' && c != EOF)
{
*ptr = c;
ptr++;
}
*ptr = '\0';
ptr = City10;
printf("Please enter tenth city: ");
while((c = getchar()) != '\n' && c != EOF)
{
*ptr = c;
ptr++;
}
*ptr = '\0';
//sort cities
c=1;
while(c)
{
c=0;
if(strcmp(City1, City2) > 0)
{
c=1;
*ptr=*City1;
*City1=*City2;
*City2=*ptr;
*ptr='\0';
}
if(strcmp(City2, City3) > 0)
{
c=1;
*ptr=*City2;
*City2=*City3;
*City3=*ptr;
*ptr='\0';
}
if(strcmp(City3, City4) > 0)
{
c=1;
*ptr=*City3;
*City3=*City4;
*City4=*ptr;
*ptr='\0';
}
if(strcmp(City4, City5) > 0)
{
c=1;
*ptr=*City4;
*City4=*City5;
*City5=*ptr;
*ptr='\0';
}
if(strcmp(City5, City6) > 0)
{
c=1;
*ptr=*City5;
*City5=*City6;
*City6=*ptr;
*ptr='\0';
}
if(strcmp(City6, City7) > 0)
{
c=1;
*ptr=*City6;
*City6=*City7;
*City7=*ptr;
*ptr='\0';
}
if(strcmp(City7, City8) > 0)
{
c=1;
*ptr=*City7;
*City7=*City8;
*City8=*ptr;
*ptr='\0';
}
if(strcmp(City8, City9) > 0)
{
c=1;
*ptr=*City8;
*City8=*City9;
*City9=*ptr;
*ptr='\0';
}
if(strcmp(City9, City10) > 0)
{
c=1;
*ptr=*City9;
*City9=*City10;
*City10=*ptr;
*ptr='\0';
}
}
puts(City1); // Print out the string
puts(City2); puts(City3);
puts(City4); puts(City5);
puts(City6); puts(City7);
puts(City8); puts(City9);
puts(City10);
free(City1); // Free the reserved memory
free(City2); free(City3); free(City4); free(City5);
free(City6); free(City7); free(City8); free(City9); free(City10);
return 0;
}
That's horrible. You need to learn what an array is fast.
Quzah.
It's my homework and I have to use strings. If I could, I would write this prog using something different, may be arrays. Believe me, I do not program for money =)Quote:
Originally Posted by quzah
i think he was referring to your char*s.
you have X-number of char arrays (char*s). and when you want to do something to them, you have repeated code X-number of times. it would be more manageable, better structured, and easier to read if you made an array of char*s, that is, a 'char**'. you could reduce your code significantly.
Hm-m-m... didn't know this. May be I should create a function, which compares and switch two pointers?Quote:
Originally Posted by nadroj
Anyway, this program isn't working now... :(
Can anyone tell me, how to change strings? Everything goes good until program find first string to change with next string. Then first char is from previous string, but all the other - from itself. And so goes on =(
Here's an example that works but doesn't do your homework for you. Read it, learn it, love it :)
My output:Code:#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int compare(const void *str1, const void *str2)
{
return (strcmp(*(char **)str1, *(char **)str2) > 0);
}
int main(void)
{
char **cities;
char buf[7];
int i;
cities = malloc(sizeof(*cities) * 10);
for(i = 0;i < 10;++i)
{
sprintf(buf, "City%d", rand() % 100);
cities[i] = malloc(strlen(buf) + 1);
strcpy(cities[i], buf);
}
qsort(cities, 10, sizeof(*cities), compare);
for(i = 0;i < 10;++i)
puts(cities[i]);
for(i = 0;i < 10;++i)
free(cities[i]);
free(cities);
return 0;
}
Quote:
itsme@dreams:~/C$ ./arrstrs
City15
City21
City35
City49
City77
City83
City86
City86
City92
City93
What means rand()? It's randomize function?
Maybe you have Skype to contact you?