ctype.3

操作系统设计与实现源码

.\"	@(#)ctype.3	6.4 (Berkeley) 5/12/86
.\"
.TH CTYPE 3  "May 12, 1986"
.AT 3
.SH NAME
ctype, isalpha, isupper, islower, isdigit, isxdigit, isalnum, isspace, ispunct, isprint, isgraph, iscntrl, isascii, toupper, tolower, toascii \- character classification macros
.SH SYNOPSIS
.nf
.ft B
#include <ctype.h>

int isalpha(int \fIc\fP)
\&...
.fi
.SH DESCRIPTION
These macros classify characters
by table lookup.
Each is a predicate returning nonzero for true,
zero for false.
.B Isascii
and
.B toascii
are defined on all integer values; the rest
are defined only on the range of
.B "unsigned char"
and on the special value
EOF (see
.BR stdio (3)).
.TP 15n
.B isalpha
.I c
is a letter
.TP
.B isupper
.I c
is an upper case letter
.TP
.B islower 
.I c
is a lower case letter
.TP
.B isdigit
.I c
is a digit
.TP
.B isxdigit
.I c
is a hex digit
.TP
.B isalnum
.I c
is an alphanumeric character
.TP
.B isspace
.I c
is a space, tab, carriage return, newline, vertical tab, or formfeed
.TP
.B ispunct
.I c
is a punctuation character (neither control nor alphanumeric)
.TP
.B isprint
.I c
is a printing character, code 040(8) (space) through 0176 (tilde)
.TP
.B isgraph
.I c
is a printing character, similar to
.B isprint
except false for space.
.TP
.B iscntrl
.I c
is a delete character (0177) or ordinary control character
(less than 040).
.TP
.B isascii
.I c
is an ASCII character, code less than 0200
.TP
.B tolower
.I c
is converted to lower case.  Return value is undefined if not 
.BR isupper (\fIc\fR).
.TP
.B toupper
.I c
is converted to upper case.  Return value is undefined if not 
.BR islower (\fIc\fR).
.TP
.B toascii
.I c
is converted to be a valid ascii character.
.SH "SEE ALSO"
.BR ascii (7)