CODEWITHSUNDEEP
cstringintegerextract
YAKOVM
YAKOVM

Reputation: 10153

integer extraction from string

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 ,including 0. After the integer sequence follows sequence of chars which are not integer representation. for example "23meeting","1h". Is there some (builtin) C function which can extract the integer? For example for "23meeting" such operation could be performed : 

int x = needed_function("23meeting"); //results x = 23

Thanks

Upvotes: 0

Views: 8179

Answers (5)

Guy Sirton
Guy Sirton

Reputation: 8401

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).

Upvotes: 1

Sunny
Sunny

Reputation: 14808

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);
}

Upvotes: 2

Blagovest Buyukliev
Blagovest Buyukliev

Reputation: 43508

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.

Upvotes: 1

sidyll
sidyll

Reputation: 59287

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).

Upvotes: 1

Sean Bright
Sean Bright

Reputation: 120644

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

Upvotes: 0

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