conv(3C)

conv: toupper, tolower, _toupper, _tolower, toascii -- translate characters

Synopsis

   #include <ctype.h>
   
   int toupper(int c);
   

   int tolower(int c);
   

   int _toupper(int c);
   

   int _tolower(int c);
   

   int toascii(int c);

Description

toupper and tolower have as their domain the range of the function getc: all values represented in an unsigned char and the value of the macro EOF as defined in stdio.h. If the argument of toupper represents a lowercase letter, the result is the corresponding uppercase letter. If the argument of tolower represents an uppercase letter, the result is the corresponding lowercase letter. All other arguments in the domain are returned unchanged.

The macros _toupper and _tolower accomplish the same things as toupper and tolower, respectively, but have restricted domains and are faster. _toupper requires a lowercase letter as its argument; its result is the corresponding uppercase letter. _tolower requires an uppercase letter as its argument; its result is the corresponding lowercase letter. Arguments outside the domain cause undefined results.

toascii yields its argument with all bits turned off that are not part of a standard 7-bit ASCII character; it is intended for compatibility with other systems.

toupper, tolower, _toupper, and_tolower are affected by LC_CTYPE. In the C locale, or in a locale where shift information is not defined, these functions determine the case of characters according to the rules of the ASCII-coded character set. Characters outside the ASCII range of characters are returned unchanged.

All the conversion functions and macros use a table lookup.

References

ctype(3C), environ(5), getc(3S), setlocale(3C), wconv(3C)