whats wrong with this pointer?

[Dan]

Hi, I am getting a SEG V at line 12 and just can't figure out why?
Can you help please? This is a simple program to replace spaces with '_' in string
1 #include <stdio.h>
2
3 int main()
4 {
5 char *ptr;
6 ptr="Beginning Linux Programming.pdf ";
7
8 printf("ptr=%s\ n", ptr);
9 while(*ptr!='\0 ')
10 {
11 if((*ptr)==' ' || (*ptr)==' ')
12 *ptr='_';
13 ptr++;
14 }
15 printf("%s\n",p tr);
16 printf("\n");
17 }
Thanks!

../a.out
ptr=Beginning Linux Programming.pdf
Segmentation fault

[Artie Gold]

Dan wrote:

Hi, I am getting a SEG V at line 12 and just can't figure out why?
Can you help please? This is a simple program to replace spaces with '_' in string
1 #include <stdio.h>
2
3 int main()
4 {
5 char *ptr;
6 ptr="Beginning Linux Programming.pdf ";
7
8 printf("ptr=%s\ n", ptr);
9 while(*ptr!='\0 ')
10 {
11 if((*ptr)==' ' || (*ptr)==' ')
12 *ptr='_';
13 ptr++;
14 }
15 printf("%s\n",p tr);
16 printf("\n");
17 }
Thanks!

./a.out
ptr=Beginning Linux Programming.pdf
Segmentation fault

Obviously you've neither read the FAQ nor lurked before posting. Being a
responsible citizen of usenet requires you do both.

HTH,
--ag

--
Artie Gold -- Austin, Texas
http://it-matters.blogspot.com (new post 12/5)
http://www.cafepress.com/goldsays

[CBFalconer]

Dan wrote:

Hi, I am getting a SEG V at line 12 and just can't figure out why?
Can you help please? This is a simple program to replace spaces
with '_' in string
1 #include <stdio.h>
2
3 int main()
4 {
5 char *ptr;
6 ptr="Beginning Linux Programming.pdf ";
7
8 printf("ptr=%s\ n", ptr);
9 while(*ptr!='\0 ')
10 {
11 if((*ptr)==' ' || (*ptr)==' ')
12 *ptr='_';
13 ptr++;
14 }
15 printf("%s\n",p tr);
16 printf("\n");
17 }
Thanks!

./a.out
ptr=Beginning Linux Programming.pdf
Segmentation fault

Of course it fails. ptr has been set to point to a non-modifiable
string, which you then attempt to modify. You might try declaring
it as:

ptr[] = "Beginning Linux Programming.pdf ";

which changes it from an initialized pointer to an initialized
array.

--
"If you want to post a followup via groups.google.c om, don't use
the broken "Reply" link at the bottom of the article. Click on
"show options" at the top of the article, then click on the
"Reply" at the bottom of the article headers." - Keith Thompson

[MJ]

Hi
if you do like this it will work fine
#include <stdio.h>

int main()
{
char *ptr;
char ptr1[]="Beginning Linux Programming.pdf ";
ptr = ptr1;

printf("ptr=%s\ n", ptr);
while(*ptr!='\0 ')
{
if((*ptr)==' ' || (*ptr)==' ')
*ptr='_';
ptr++;
}
printf("%s\n",p tr1);
printf("\n");
}
Regards
MJ

[pete]

MJ wrote:

if((*ptr)==' ' || (*ptr)==' ')

I'm pretty sure that if (*ptr) equals ' ',
then (*ptr) will also be equal to ' '.

--
pete

[Dag-Erling Smørgrav]

pete <pf*****@mindsp ring.com> writes:

MJ wrote:

if((*ptr)==' ' || (*ptr)==' ')

I'm pretty sure that if (*ptr) equals ' ',
then (*ptr) will also be equal to ' '.

one of those should be '\t'.

DES
--
Dag-Erling Smørgrav - de*@des.no