| ctype.h | Header File

Header File Index

Routines for checking and changing character types

Functions

_tolower
  Translates uppercase characters to lowercase.
_toupper
  Translates uppercase characters to lowercase.
isalnum
  Checks whether a character is an alphanumeric.
isalpha
  Checks whether a character is a letter.
isascii
  Checks whether a character is an ASCII character.
iscntrl
  Checks whether a character is a control character.
isdigit
  Checks whether a character is a digit.
isextalnum
  Checks whether a character is an extended alphanumeric.
isextlower
  Checks whether a character is a lowercase, including foreign ones.
isextpunct
  Checks whether a character is an extended punctuation character.
isextupper
  Checks whether a character is an uppercase, including foreign ones.
isfrgn
  Checks whether a character is a foreign letter.
isfrgnalnum
  Checks whether a character is a foreign letter which is valid in a variable name.
isfrgnlower
  Checks whether a character is a foreign lowercase.
isfrgnupper
  Checks whether a character is a foreign uppercase.
isgraph
  Checks whether a character is a graph character.
isGreek
  Checks whether a character is a Greek letter.
islower
  Checks whether a character is a lowercase.
isprint
  Checks whether a character is a printing character.
ispunct
  Checks whether a character is a punctuation character.
isspace
  Checks whether a character is a white space.
isupper
  Checks whether a character is an uppercase.
isxdigit
  Checks whether a character is a hex digit.
toascii
  Translates characters to ASCII format.
toextlower
  Translates characters to lowercase, including foreign ones.
toextupper
  Translates characters to uppercase, including foreign ones.
tolower
  Translates characters to lowercase.
toupper
  Translates characters to uppercase.

Note: All of these functions are inline functions which are implemented using GNU C smart macros (except the simplest ones, which are ordinary macros). Some of them expand to relatively large code, so if you call any of them more than twice in a program, it will be a good idea to define an ordinary function which calls this macro. For example, if you want to call isxdigit more than twice, define the following to save memory:

    int _isxdigit(int c)
    {
      return isxdigit (c);
    }

Then call _isxdigit instead.