C标准库函数检查char *是否为单词？

Question

After reading in a line from a file and splitting that line into tokens, I need to check if the token only contains alphabetic characters [a-zA-Z]. Is there some sort of function in the C Standard Library to check this? I could use regex.h to check this but I think this is overblown.

Sure, I could write a function that loops over the token and checks every char, but I don't want to reinvent the wheel.

PS: Using a third party library is not an option.

Answer 1

Certainly:

#include <ctype.h>

int isalpha(int ch) // is alphabetic?
int isalnum(int ch) // is alphanumeric?

Answer 2

You have all these functions defined in ctype.h

   int isalnum(int c);
   int isalpha(int c);
   int iscntrl(int c);
   int isdigit(int c);
   int isgraph(int c);
   int islower(int c);
   int isprint(int c);
   int ispunct(int c);
   int isspace(int c);
   int isupper(int c);
   int isxdigit(int c);

Answer 3

As stated by Kos, isalpha(int ch) and isalnum(int ch) , but those are not char* functions. Coding your own with isalpha and is alnum should be quite easy, though you must be careful : if you are going to deal with special characters, check your locale (isalpha depends on them).

Answer 4

Strspn will do the job.

The basic concept is that you give it a string, and returns the length of the longest piece that consists of characters in your specific list. add az and AZ to that list. If the value back from strspn is the same as the strlen, you are good to go.

Answer 5

C Standard Library is very short on char* related functions. Please check this link to see if anythings helps: http://www.cplusplus.com/reference/clibrary/cstring/