How to check whether a char pointer is an empty string?

[dipuks]

Hey I have a variable, char * p which could sometimes have a string or sometimes it will be empty. How to check whether "p" has a string in it or not? I see that its not possible to do something like, if(p != "") { } Thanks

[krmed]

Perhaps you could use

if(*p = 0);

But then this assumes you initialize the pointer when it is emptied.

char* p = NULL;
// use your pointer
p = &some_char_array;
// do whatever with it
p = NULL;

Hope that helps.

Karl - WK5M PP-ASEL-IA (N43CS) PGP Key: 0xDB02E193 PGP Key Fingerprint: 8F06 5A2E 2735 892B 821C 871A 0411 94EA DB02 E193

[Lost User]

krmed wrote:

if(*p = 0);

Don't you mean == there?

[CPallini]

you may check for an empty string with

if (strlen(p)==0)
{
//..
}

the above check, of course, assumes p pointing to a valid string (empty string is a valid one). i.e. such code doesn't check if p is a valid pointer, to spot the difference, try:

char *p, *q;
p="";
q=NULL;

printf("strlen(p)=%d\n", strlen(p));
printf("strlen(q)=%d\n", strlen(q));

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
[My articles]

[krmed]

Yes, of course! Just typed too fast.

Karl - WK5M PP-ASEL-IA (N43CS) PGP Key: 0xDB02E193 PGP Key Fingerprint: 8F06 5A2E 2735 892B 821C 871A 0411 94EA DB02 E193

[Tim Craig]

If you set p equal to NULL and then dereference it with *p, you'll get a crash. Maybe if you set *p = '\0' or *p = "\0".

You measure democracy by the freedom it gives its dissidents, not the freedom it gives its assimilated conformists.

[Fatbuddha 1]

Why not use a string type? There you can check easily. However, if you have to use a char *, then you have to care about setting the pointer to NULL or to a '\0' char. this would be the end of a string. As you like. The cleaner version, I would say, would be to use a string object. Cheers

You have the thought that modern physics just relay on assumptions, that somehow depends on a smile of a cat, which isn’t there.( Albert Einstein)