man3/isalpha.3

   1 .\" Copyright (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de)
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  25 .\" Modified Sat Jul 24 19:10:00 1993 by Rik Faith (faith@cs.unc.edu)
  26 .\" Modified Sun Aug 21 17:51:50 1994 by Rik Faith (faith@cs.unc.edu)
  27 .\" Modified Sat Sep  2 21:52:01 1995 by Jim Van Zandt <jrv@vanzandt.mv.com>
  28 .\" Modified Mon May 27 22:55:26 1996 by Martin Schulze (joey@linux.de)
  29 .\"
  30 .TH ISALPHA 3 2010-09-20 "GNU" "Linux Programmer's Manual"
  31 .SH NAME
  32 isalnum, isalpha, isascii, isblank, iscntrl, isdigit, isgraph, islower,
  33 isprint, ispunct, isspace, isupper, isxdigit \- character
  34 classification routines
  35 .SH SYNOPSIS
  36 .nf
  37 .B #include <ctype.h>
  38 .sp
  39 .BI "int isalnum(int " "c" );
  40 .br
  41 .BI "int isalpha(int " "c" );
  42 .br
  43 .BI "int isascii(int " "c" );
  44 .br
  45 .BI "int isblank(int " "c" );
  46 .br
  47 .BI "int iscntrl(int " "c" );
  48 .br
  49 .BI "int isdigit(int " "c" );
  50 .br
  51 .BI "int isgraph(int " "c" );
  52 .br
  53 .BI "int islower(int " "c" );
  54 .br
  55 .BI "int isprint(int " "c" );
  56 .br
  57 .BI "int ispunct(int " "c" );
  58 .br
  59 .BI "int isspace(int " "c" );
  60 .br
  61 .BI "int isupper(int " "c" );
  62 .br
  63 .BI "int isxdigit(int " "c" );
  64 .fi
  65 .sp
  66 .in -4n
  67 Feature Test Macro Requirements for glibc (see
  68 .BR feature_test_macros (7)):
  69 .in
  70 .sp
  71 .ad l
  72 .BR isascii ():
  73 .RS 4
  74 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE
  75 .br
  76 .RE
  77 .BR isblank ():
  78 .RS 4
  79 _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
  80 _POSIX_C_SOURCE\ >=\ 200112L;
  81 .br
  82 or
  83 .I cc\ -std=c99
  84 .RE
  85 .ad
  86 .SH DESCRIPTION
  87 These functions check whether
  88 .IR c ,
  89 which must have the value of an
  90 .I unsigned char
  91 or
  92 .BR EOF ,
  93 falls into a certain character class according to the current locale.
  94 .TP
  95 .BR isalnum ()
  96 checks for an alphanumeric character; it is equivalent to
  97 .BI "(isalpha(" c ") || isdigit(" c "))" \fR.
  98 .TP
  99 .BR isalpha ()
 100 checks for an alphabetic character; in the standard \fB"C"\fP
 101 locale, it is equivalent to
 102 .BI "(isupper(" c ") || islower(" c "))" \fR.
 103 In some locales, there may be additional characters for which
 104 .BR isalpha ()
 105 is true\(emletters which are neither upper case nor lower
 106 case.
 107 .TP
 108 .BR isascii ()
 109 checks whether \fIc\fP is a 7-bit
 110 .I unsigned char
 111 value that fits into
 112 the ASCII character set.
 113 .TP
 114 .BR isblank ()
 115 checks for a blank character; that is, a space or a tab.
 116 .TP
 117 .BR iscntrl ()
 118 checks for a control character.
 119 .TP
 120 .BR isdigit ()
 121 checks for a digit (0 through 9).
 122 .TP
 123 .BR isgraph ()
 124 checks for any printable character except space.
 125 .TP
 126 .BR islower ()
 127 checks for a lower-case character.
 128 .TP
 129 .BR isprint ()
 130 checks for any printable character including space.
 131 .TP
 132 .BR ispunct ()
 133 checks for any printable character which is not a space or an
 134 alphanumeric character.
 135 .TP
 136 .BR isspace ()
 137 checks for white-space characters.
 138 In the
 139 .B """C"""
 140 and
 141 .B """POSIX"""
 142 locales, these are: space, form-feed
 143 .RB ( \(aq\ef\(aq ),
 144 newline
 145 .RB ( \(aq\en\(aq ),
 146 carriage return
 147 .RB ( \(aq\er\(aq ),
 148 horizontal tab
 149 .RB ( \(aq\et\(aq ),
 150 and vertical tab
 151 .RB ( \(aq\ev\(aq ).
 152 .TP
 153 .BR isupper ()
 154 checks for an uppercase letter.
 155 .TP
 156 .BR isxdigit ()
 157 checks for a hexadecimal digits, that is, one of
 158 .br
 159 .BR "0 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F" .
 160 .SH RETURN VALUE
 161 The values returned are nonzero if the character
 162 .I c
 163 falls into the tested class, and a zero value
 164 if not.
 165 .SH CONFORMING TO
 166 C99, 4.3BSD.
 167 C89 specifies all of these functions except
 168 .BR isascii ()
 169 and
 170 .BR isblank ().
 171 .BR isascii ()
 172 is a BSD extension
 173 and is also an SVr4 extension.
 174 .BR isblank ()
 175 conforms to POSIX.1-2001 and C99 7.4.1.3.
 176 POSIX.1-2008 marks
 177 .BR isascii ()
 178 as obsolete,
 179 noting that it cannot be used portably in a localized application.
 180 .SH NOTES
 181 The details of what characters belong into which class depend on the current
 182 locale.
 183 For example,
 184 .BR isupper ()
 185 will not recognize an A-umlaut (\(:A) as an uppercase letter in the default
 186 .B "C"
 187 locale.
 188 .SH SEE ALSO
 189 .BR iswalnum (3),
 190 .BR iswalpha (3),
 191 .BR iswblank (3),
 192 .BR iswcntrl (3),
 193 .BR iswdigit (3),
 194 .BR iswgraph (3),
 195 .BR iswlower (3),
 196 .BR iswprint (3),
 197 .BR iswpunct (3),
 198 .BR iswspace (3),
 199 .BR iswupper (3),
 200 .BR iswxdigit (3),
 201 .BR setlocale (3),
 202 .BR toascii (3),
 203 .BR tolower (3),
 204 .BR toupper (3),
 205 .BR ascii (7),
 206 .BR locale (7)