1.\" $NetBSD: ctype.3,v 1.23 2017/12/12 14:13:52 abhinav Exp $ 2.\" 3.\" Copyright (c) 1991 Regents of the University of California. 4.\" All rights reserved. 5.\" 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)ctype.3 6.5 (Berkeley) 4/19/91 32.\" 33.Dd December 8, 2017 34.Dt CTYPE 3 35.Os 36.Sh NAME 37.Nm ctype 38.Nd character classification and mapping functions 39.Sh LIBRARY 40.Lb libc 41.Sh SYNOPSIS 42.In ctype.h 43.Fn isalpha "int c" 44.Fn isupper "int c" 45.Fn islower "int c" 46.Fn isdigit "int c" 47.Fn isxdigit "int c" 48.Fn isalnum "int c" 49.Fn isspace "int c" 50.Fn ispunct "int c" 51.Fn isprint "int c" 52.Fn isgraph "int c" 53.Fn iscntrl "int c" 54.Fn isblank "int c" 55.Fn toupper "int c" 56.Fn tolower "int c" 57.Sh DESCRIPTION 58The above functions perform character tests and conversions on the integer 59.Ar c . 60.Pp 61See the specific manual pages for information about the 62test or conversion performed by each function. 63.Sh EXAMPLES 64To print an upper-case version of a string to stdout, 65the following code can be used: 66.Bd -literal -offset indent 67const char *s = "xyz"; 68 69while (*s != '\e0') { 70 putchar(toupper((unsigned char)*s)); 71 s++; 72} 73.Ed 74.Sh SEE ALSO 75.Xr isalnum 3 , 76.Xr isalpha 3 , 77.Xr isblank 3 , 78.Xr iscntrl 3 , 79.Xr isdigit 3 , 80.Xr isgraph 3 , 81.Xr islower 3 , 82.Xr isprint 3 , 83.Xr ispunct 3 , 84.Xr isspace 3 , 85.Xr isupper 3 , 86.Xr isxdigit 3 , 87.Xr tolower 3 , 88.Xr toupper 3 , 89.Xr ascii 7 90.Sh STANDARDS 91These functions, with the exception of 92.Fn isblank , 93conform to 94.St -ansiC . 95All described functions, including 96.Fn isblank , 97also conform to 98.St -p1003.1-2001 . 99.Sh CAVEATS 100The first argument of these functions is of type 101.Vt int , 102but only a very restricted subset of values are actually valid. 103The argument must either be the value of the macro 104.Dv EOF 105(which has a negative value), 106or must be a non-negative value within the range representable as 107.Vt unsigned char . 108Passing invalid values leads to undefined behavior. 109.Pp 110Values of type 111.Vt int 112that were returned by 113.Xr getc 3 , 114.Xr fgetc 3 , 115and similar functions or macros 116are already in the correct range, and may be safely passed to these 117.Nm ctype 118functions without any casts. 119.Pp 120Values of type 121.Vt char 122or 123.Vt signed char 124must first be cast to 125.Vt unsigned char , 126to ensure that the values are within the correct range. 127Casting a negative-valued 128.Vt char 129or 130.Vt signed char 131directly to 132.Vt int 133will produce a negative-valued 134.Vt int , 135which will be outside the range of allowed values 136(unless it happens to be equal to 137.Dv EOF , 138but even that would not give the desired result). 139