man3/isalpha.3

   1 .\" (c) 1993 by Thomas Koenig (ig25@rz.uni-karlsruhe.de)
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  24 .\" Modified Sat Jul 24 19:10:00 1993 by Rik Faith (faith@cs.unc.edu)
  25 .\" Modified Sun Aug 21 17:51:50 1994 by Rik Faith (faith@cs.unc.edu)
  26 .\" Modified Sat Sep  2 21:52:01 1995 by Jim Van Zandt <jrv@vanzandt.mv.com>
  27 .\" Modified Mon May 27 22:55:26 1996 by Martin Schulze (joey@linux.de)
  28 .\"
  29 .TH ISALPHA 3  1995-09-02 "GNU" "Linux Programmer's Manual"
  30 .SH NAME
  31 isalnum, isalpha, isascii, isblank, iscntrl, isdigit, isgraph, islower,
  32 isprint, ispunct, isspace, isupper, isxdigit \- character
  33 classification routines
  34 .SH SYNOPSIS
  35 .nf
  36 .B #include <ctype.h>
  37 .sp
  38 .BI "int isalnum(int " "c" );
  39 .nl
  40 .BI "int isalpha(int " "c" );
  41 .nl
  42 .BI "int isascii(int " "c" );
  43 .nl
  44 .BI "int isblank(int " "c" );
  45 .nl
  46 .BI "int iscntrl(int " "c" );
  47 .nl
  48 .BI "int isdigit(int " "c" );
  49 .nl
  50 .BI "int isgraph(int " "c" );
  51 .nl
  52 .BI "int islower(int " "c" );
  53 .nl
  54 .BI "int isprint(int " "c" );
  55 .nl
  56 .BI "int ispunct(int " "c" );
  57 .nl
  58 .BI "int isspace(int " "c" );
  59 .nl
  60 .BI "int isupper(int " "c" );
  61 .nl
  62 .BI "int isxdigit(int " "c" );
  63 .fi
  64 .SH DESCRIPTION
  65 These functions check whether
  66 .IR c ,
  67 which must have the value of an
  68 .B unsigned char
  69 or
  70 .BR EOF ,
  71 falls into a certain character class according to the current locale.
  72 .TP
  73 .B "isalnum()"
  74 checks for an alphanumeric character; it is equivalent to
  75 .BI "(isalpha(" c ") || isdigit(" c "))" \fR.
  76 .TP
  77 .B "isalpha()"
  78 checks for an alphabetic character; in the standard \fB"C"\fP
  79 locale, it is equivalent to
  80 .BI "(isupper(" c ") || islower(" c "))" \fR.
  81 In some locales, there may be additional characters for which
  82 .B  isalpha()
  83 is true--letters which are neither upper case nor lower
  84 case.
  85 .TP
  86 .B "isascii()"
  87 checks whether \fIc\fP is a 7-bit
  88 .I unsigned char
  89 value that fits into
  90 the ASCII character set.  This function is a BSD extension
  91 and is also an SVID extension.
  92 .TP
  93 .B "isblank()"
  94 checks for a blank character; that is, a space or a tab.
  95 .TP
  96 .B "iscntrl()"
  97 checks for a control character.
  98 .TP
  99 .B "isdigit()"
 100 checks for a digit (0 through 9).
 101 .TP
 102 .B "isgraph()"
 103 checks for any printable character except space.
 104 .TP
 105 .B "islower()"
 106 checks for a lower-case character.
 107 .TP
 108 .B "isprint()"
 109 checks for any printable character including space.
 110 .TP
 111 .B "ispunct()"
 112 checks for any printable character which is not a space or an
 113 alphanumeric character.
 114 .TP
 115 .B "isspace()"
 116 checks for white-space characters.  In the
 117 .B """C"""
 118 and
 119 .B """POSIX"""
 120 locales, these are: space, form-feed
 121 .RB ( '\ef' ),
 122 newline
 123 .RB ( '\en' ),
 124 carriage return
 125 .RB ( '\er' ),
 126 horizontal tab
 127 .RB ( '\et' ),
 128 and vertical tab
 129 .RB ( '\ev' ).
 130 .TP
 131 .B "isupper()"
 132 checks for an uppercase letter.
 133 .TP
 134 .B "isxdigit()"
 135 checks for a hexadecimal digits, i.e. one of
 136 .nl
 137 .BR "0 1 2 3 4 5 6 7 8 9 a b c d e f A B C D E F" .
 138 .SH "RETURN VALUE"
 139 The values returned are nonzero if the character
 140 .I c
 141 falls into the tested class, and a zero value
 142 if not.
 143 .SH "CONFORMING TO"
 144 ANSI - C, BSD 4.3.
 145 \fBisascii()\fP is a BSD extension
 146 and is also an SVID extension.
 147 \fBisblank()\fP conforms to ISO C99 7.4.1.3.
 148 .SH NOTE
 149 The details of what characters belong into which class depend on the current
 150 locale.  For example,
 151 .B isupper()
 152 will not recognize an A - umlaut as an uppercase letter in the default
 153 .B "C"
 154 locale.
 155 .SH "SEE ALSO"
 156 .BR setlocale (3),
 157 .BR tolower (3),
 158 .BR toupper (3),
 159 .BR ascii (7),
 160 .BR locale (7)