How do I find the index of a character within a string in C

Question

Suppose I have a string  qwerty  and I wish to find the index position of the e character in it   In this case the index would be 2   How do I do it in C    I found the strchr function but it returns a pointer to a character and not the index

User · Answer

void myFunc char  str  char c        char  ptr      int index       ptr   strchr str  c       if  ptr    NULL                printf  Character not found n            return             index   ptr - str       printf  The index is  d n   index       ASSERT str index     c       Verify that the character at index is the one we want      This code is currently untested  but it demonstrates the proper concept

User · Answer

You can also use strcspn string   e   but this may be much slower since it s able to handle searching for multiple possible characters  Using strchr and subtracting the pointer is the best way

User · Answer

What about   char  string    qwerty   char  e   string  int idx   0  while   e       e   idx      copying to e to preserve the original string  I suppose if you don t care you could just operate over  string

User · Answer

Just subtract the string address from what strchr returns   char  string    qwerty   char  e  int index   e   strchr string   e    index    int  e - string     Note that the result is zero based  so in above example it will be 2

User · Answer

This should do it     Returns the index of the first occurence of char c in char  string  If not found -1 is returned  int get index char  string  char c        char  e   strchr string  c       if  e    NULL            return -1            return  int  e - string

[c] How do I find the index of a character within a string in C?

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