ISDIGIT (3) | C library functions | Unix Manual Pages | :man▋
isdigit, isnumber - decimal-digit character test
.In ctype.h int isdigit "int c" int isnumber "int c"
The isdigit function tests for a decimal digit character. Regardless of locale, this includes the following characters only:
| "0 1 2 3 4" |
"5 6 7 8 9"
| || |
The isnumber function behaves similarly to isdigit, but may recognize additional characters, depending on the current locale setting.
For single C char s locales (see multibyte(3)) the value of the argument is representable as an unsigned char or the value of EOF.
The isdigit and isnumber functions return zero if the character tests false and returns non-zero if the character tests true.
The BSD 4.4 extension of accepting arguments outside of the range of the
.Vt "unsigned char" type in locales with large character sets is considered obsolete and may not be supported in future releases. The iswdigit function should be used instead.
ctype(3), iswdigit(3), multibyte(3), ascii(7)