How to check a character value in C
Learn how to check a character value in C
When working in C, we can use the ctype.h
standard library set of functions to check the value of a char
type variable.
We have access to several useful checks:
isalnum()
checks if a character is alphanumericisalpha()
checks if a character is alphabeticiscntrl()
checks if a character is a control characterisdigit()
checks if a character is a digitisgraph()
checks if a character is a printable ASCII character (but not a space)islower()
checks if a character is lowercaseisprint()
checks if a character is a printable ASCII characterispunct()
checks if a character is a punctuation character (a printable char, not a space, not alphanumeric)isspace()
checks if a character is a whitespace character (see more later)isupper()
checks if a character is uppercaseisxdigit()
checks if a character is an hexadecimal digit (0
-F
)
I mentioned that isspace()
checks if a character is a whitespace character. What is a whitespace character?
- Horizontal tab (HT),
'\t'
, character 9 of the ASCII table - Vertical tab (VT),
'\v'
, character 11 of the ASCII table - Form Feed (FF),
'\f'
, character 12 of the ASCII table - Carriage Return (CR),
'\r'
, character 13 of the ASCII table - Space,
' '
, character 32 of the ASCII table - New line,
'\n'
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