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Added a warning about a wrong usage, which is nevertheless often found

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in real code, and an example code that does it correctly.
This commit is contained in:
rillig 2007-01-18 08:33:34 +00:00
parent 6a0b5a67e6
commit 8b4906df56
1 changed files with 21 additions and 2 deletions
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23
lib/libc/gen/ctype.3
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@ -1,4 +1,4 @@
.\" $NetBSD: ctype.3,v 1.14 2006/02/04 18:47:31 wiz Exp $
.\" $NetBSD: ctype.3,v 1.15 2007/01/18 08:33:34 rillig Exp $
.\"
.\" Copyright (c) 1991 Regents of the University of California.
.\" All rights reserved.
@ -30,7 +30,7 @@
.\"
.\" @(#)ctype.3 6.5 (Berkeley) 4/19/91
.\"
.Dd January 26, 2006
.Dd January 18, 2006
.Dt CTYPE 3
.Os
.Sh NAME
@ -78,6 +78,25 @@ The above functions perform character tests and conversions on the integer
.Ar c .
.Pp
See the specific manual pages for more information.
.Sh CAVEATS
The first parameter of these functions is of type int, but only a very
restricted subset is actually valid as an argument.
The argument must either be the value of the macro
.Dv EOF
or representable as an unsigned char.
When testing an expression having the type
.Tn plain char ,
the argument should be cast to an unsigned char.
.Sh EXAMPLES
To print an upper-case version of a string on stdout, use the following
code:
.Bd -literal
const char *s = ...;
while (*s != '\\0') {
putchar(toupper((unsigned char)*s));
s++;
}
.Ed
.Sh SEE ALSO
.Xr isalnum 3 ,
.Xr isalpha 3 ,