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466
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1 <refentry id="isalpha">
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2 <refnamediv>
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570
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3 <refname>Isalpha</refname>
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4 <refname>Isupper</refname>
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5 <refname>Islower</refname>
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6 <refname>Isdigit</refname>
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7 <refname>Isalnum</refname>
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8 <refname>Isspace</refname>
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9 <refname>Ispunct</refname>
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10 <refname>Isprint</refname>
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11 <refname>Iscntrl</refname>
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12 <refname>Isascii</refname>
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13 <refpurpose>character classification</refpurpose>
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466
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14 </refnamediv>
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15
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16 <refsynopsisdiv>
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17 <funcsynopsis>
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468
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18 <funcsynopsisinfo>
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19 #include <ctype.h>
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20 </funcsynopsisinfo>
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570
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21
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466
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22 <funcprototype>
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23 <funcdef><function>isalpha</function></funcdef>
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570
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24 <paramdef>int <parameter>c</parameter></paramdef>
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466
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25 </funcprototype>
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26 </funcsynopsis>
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27
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28 </refsynopsisdiv>
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29
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30 <refsect1><title>Description</title>
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31 <para>
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601
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32 These functions use table look-up to classify characters
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33 according to their ascii value. The header file defines them
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34 as macros which means that they are implemented as fast, inline
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35 code rather than subroutines.
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36 </para>
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37 <para>
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38 Each results in non-zero for true or zero for false.
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39 </para>
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40 <para>
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41 The correct value is guaranteed for all integer values in
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42 isascii, but the result is unpredictable in the others if the
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43 argument is outside the range -1 to 127.
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44 </para>
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45 <para>
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46 The truth tested by each function is a follows:
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466
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47 </para>
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601
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48 <informaltable frame="none">
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49 <tgroup cols="2">
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636
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50 <colspec colwidth="1in"/>
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51 <colspec colwidth="3in"/>
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601
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52 <tbody>
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53 <row>
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54 <entry>isalpha</entry>
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55 <entry>c is a letter</entry>
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56 </row>
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57 <row>
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58 <entry>isdigit</entry>
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59 <entry>c is a digit</entry>
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60 </row>
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61 <row>
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62 <entry>isupper</entry>
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63 <entry>c is an upper case letter</entry>
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64 </row>
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65 <row>
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66 <entry>islower</entry>
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67 <entry>c is a lower case letter</entry>
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68 </row>
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69 <row>
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70 <entry>isalnum</entry>
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71 <entry>c is a letter or a digit</entry>
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72 </row>
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73 <row>
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74 <entry>isspace</entry>
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75 <entry>c is a space, tab character, newline, carriage return or formfeed</entry>
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76 </row>
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77 <row>
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78 <entry>iscntrl</entry>
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79 <entry>c is a control character (0 to 32) or DEL (127)</entry>
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80 </row>
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81 <row>
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82 <entry>ispunct</entry>
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83 <entry>c is neither countrol nor alpha-numeric</entry>
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84 </row>
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85 <row>
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86 <entry>isprint</entry>
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87 <entry>c is printable (32 to 126)</entry>
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88 </row>
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89 <row>
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90 <entry>isascii</entry>
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91 <entry>c is in the range -1 to 127</entry>
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92 </row>
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93 </tbody>
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94 </tgroup>
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95 </informaltable>
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96
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466
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97 </refsect1>
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98 </refentry>
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