Since C-style strings are always terminated with the null character (\0), you can check whether the string is empty by writing
do {
...
} while (url[0] != '\0');
Alternatively, you could use the strcmp function, which is overkill but might be easier to read:
do {
...
} while (strcmp(url, ""));
Note that strcmp returns a nonzero value if the strings are different and 0 if they're the same, so this loop continues to loop until the string is empty.
Hope this helps!
Answer from templatetypedef on Stack OverflowSince C-style strings are always terminated with the null character (\0), you can check whether the string is empty by writing
do {
...
} while (url[0] != '\0');
Alternatively, you could use the strcmp function, which is overkill but might be easier to read:
do {
...
} while (strcmp(url, ""));
Note that strcmp returns a nonzero value if the strings are different and 0 if they're the same, so this loop continues to loop until the string is empty.
Hope this helps!
If you want to check if a string is empty:
if (str[0] == '\0')
{
// your code here
}
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When I try using .isEmpty() or isspace() it gives me the message that "expression must have class type" and str != "" doesn't seem to work. The type I'm using is "const char *".
Given this code:
char text[50];
if(strlen(text) == 0) {}
Followed by a question about this code:
memset(text, 0, sizeof(text));
if(strlen(text) == 0) {}
I smell confusion. Specifically, in this case:
char text[50];
if(strlen(text) == 0) {}
... the contents of text[] will be uninitialized and undefined. Thus, strlen(text) will return an undefined result.
The easiest/fastest way to ensure that a C string is initialized to the empty string is to simply set the first byte to 0.
char text[50];
text[0] = 0;
From then, both strlen(text) and the very-fast-but-not-as-straightforward (text[0] == 0) tests will both detect the empty string.
Depends on whether or not your array is holding a null-terminated string. If so, then
if(text[0] == '\0') {}
should be sufficient.
Edit: Another method would be...
if (strcmp(text, "") == 0)
which is potentially less efficient but clearly expresses your intent.
Check if the first character is '\0'. You should also probably check if your pointer is NULL.
Copychar *c = "";
if ((c != NULL) && (c[0] == '\0')) {
printf("c is empty\n");
}
You could put both of those checks in a function to make it convenient and easy to reuse.
Edit: In the if statement can be read like this, "If c is not zero and the first character of character array 'c' is not '\0' or zero, then...".
The && simply combines the two conditions. It is basically like saying this:
Copyif (c != NULL) { /* AND (or &&) */
if (c[0] == '\0') {
printf("c is empty\n");
}
}
You may want to get a good C programming book if that is not clear to you. I could recommend a book called "The C Programming Language".
The shortest version equivalent to the above would be:
Copyif (c && !c[0]) {
printf("c is empty\n");
}
My preferred method:
Copyif (*ptr == 0) // empty string
Probably more common:
Copyif (strlen(ptr) == 0) // empty string
Im not sure if im correct in calling it an empty string but i thought it would be.
#include "stdio.h"
#include "string.h"
#include "stdlib.h"
int main(void)
{
char input[136];
char partOne[6];
char partTwo[128];
fgets(input, 136, stdin); // Now i input "Hello " or "Hello"
sscanf(input, "%5s %127s", partOne, partTwo);
if(!strcmp(partTwo, ""))
printf("%s\n", "YES");
return 0;
}if I input "Hello " or "Hello" I want to detect that the char array partTwo has an empty string (i don't know what else to call it) but since the check fails then I think its not an empty string so what is it?
If I input "Hello" or "Hello " what is the value of partTwo so I can test for it using strcmp
Thank you!