NAME

isalpha —

alphabetic character test

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <ctype.h>

int
isalpha(int c);

int
isalpha_l(int c, locale_t loc);

DESCRIPTION

The isalpha() function tests for any character for which isupper(3) or islower(3) is true. The value of the argument must be representable as an unsigned char or the value of EOF.

In the ASCII character set, this includes the following characters (with their numeric values shown in octal):

101 ``A''	102 ``B''	103 ``C''	104 ``D''	105 ``E''
106 ``F''	107 ``G''	110 ``H''	111 ``I''	112 ``J''
113 ``K''	114 ``L''	115 ``M''	116 ``N''	117 ``O''
120 ``P''	121 ``Q''	122 ``R''	123 ``S''	124 ``T''
125 ``U''	126 ``V''	127 ``W''	130 ``X''	131 ``Y''
132 ``Z''	141 ``a''	142 ``b''	143 ``c''	144 ``d''
145 ``e''	146 ``f''	147 ``g''	150 ``h''	151 ``i''
152 ``j''	153 ``k''	154 ``l''	155 ``m''	156 ``n''
157 ``o''	160 ``p''	161 ``q''	162 ``r''	163 ``s''
164 ``t''	165 ``u''	166 ``v''	167 ``w''	170 ``x''
171 ``y''	172 ``z''

The isalpha_l() function takes an explicit locale argument, whereas the isalpha() function uses the current global or per-thread locale.

RETURN VALUES

The isalpha() function returns zero if the character tests false and returns non-zero if the character tests true.

COMPATIBILITY

The 4.4BSD extension of accepting arguments outside of the range of the unsigned char type in locales with large character sets is considered obsolete and may not be supported in future releases. The iswalpha() function should be used instead.

STANDARDS

The isalpha() function conforms to ISO/IEC 9899:1990 (“ISO C90”). The isalpha_l() function conforms to IEEE Std 1003.1-2008 (“POSIX.1”).