CODEWITHSUNDEEP
c++char
matthew3r
matthew3r

Reputation: 692

C++ Get a specified part from a char

I read a line from a text file, where in the end of the line there are numbers (format: "some text.001"), and I would like to get the number after the 0 or 0s. So if it's 001, then 1, if it's 010, then it's 10. What I got now:

fgets(strLine, 100, m_FileStream);
// Here I need to cut the numbers into myNum
int num = atoi(&myNum);

I tried with strrchr to get the position of the ".", but don't know what's next. Maybe I need strtok, but i don't know how to use it.

Upvotes: 1

Views: 265

Answers (4)

Component 10
Component 10

Reputation: 10507

The function strtol() (or a variant) is your friend for number conversion - prefer it to atoi() as you've got more control over conversion and error detection. For a C++ approach, you could use STL:

string s = "some text.001";
size_t p = s.find_last_of('.');
cout << (( p != string::npos ) ? strtol( s.substr(p+1).c_str(), NULL, 0 ) : -1) << endl;

Output:

1

Upvotes: 0

AudioDroid
AudioDroid

Reputation: 2322

I think this should work:

fgets(..);
int iPos = strLine.find_last_of('0');
string strNum = strLine.substr(iPos, strLine.length()-iPos);
int num = ...

http://www.cplusplus.com/reference/string/string/find_last_of/

Haven't tested it though.

Upvotes: 0

trojanfoe
trojanfoe

Reputation: 122458

This is a C solution, not C++, but should work:

const char *filename = "some text.001";
char *p = strrchr(filename, '.');
if (p != NULL)
{
    int num = atoi(p+1);
    printf("%d\n", num);
}
else
{
    // No extension
}

Upvotes: 0

hmjd
hmjd

Reputation: 122011

Once you have the position of the . you can advance by one char and use atoi():

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main()
{
    char buf[20] = "some text.010";
    char* period_ptr = strrchr(buf, '.');
    if (period_ptr)
    {
        printf("%d\n", atoi(++period_ptr));
    }
    return 0;
}

Upvotes: 4

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