integer extraction from string

Question

I have an input argument string const char* s I know that it starts the sequence of chars which are integers representation ,this sequence could be of any length ,

Answer 1

atoi() should do what you want to, although a more robust implementation would use strtol().

Answer 2

atoi() should work fine for this. It should stop at the first non-numeric character.

int x = atoi("23meeting")

EDIT: A comment implies that atoi() is not thread safe or is deprecated from the language. There is some discussion of the thread safety of this function here:

Why does OSX document atoi/atof as not being threadsafe?

Can someone provide a reference to atoi not being thread safe?

And as far as I can tell atoi() is in C99 which is the latest standard (7.20.1.2).

Answer 3

You can iterate through the string and can give the condition to get numbers

num=0;
for(i=0;str[i]!='\0';i++) {
if(str[i]>=48 && str[i]<=57)
 num=num*10+(str[i]-48);
  printf("\n%d",num);
} 

Answer 4

One way would be to use sscanf:

char *str = "23meeting";
unsigned x;
sscanf(str, "%u", &x);
printf("%u\n", x);

For additional error-checking, though, you'll have to do some additional manual checks.

Answer 5

Try atoi() or the complete strtol():

int x = atoi("23meeting");
int x = (int)strtol("23meeting", (char **)NULL, 10);

Check the man pages on your system (section 3 in Unix).