1TOUPPER(3) Linux Programmer's Manual TOUPPER(3)
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6 toupper, tolower - convert letter to upper or lower case
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9 #include <ctype.h>
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11 int toupper(int c);
12 int tolower(int c);
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15 toupper() converts the letter c to upper case, if possible.
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17 tolower() converts the letter c to lower case, if possible.
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19 If c is not an unsigned char value, or EOF, the behaviour of these
20 functions is undefined.
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23 The value returned is that of the converted letter, or c if the conver‐
24 sion was not possible.
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27 C89, C99, 4.3BSD
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30 The details of what constitutes an uppercase or lowercase letter depend
31 on the current locale. For example, the default "C" locale does not
32 know about umlauts, so no conversion is done for them.
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34 In some non-English locales, there are lowercase letters with no corre‐
35 sponding uppercase equivalent; the German sharp s is one example.
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38 isalpha(3), setlocale(3), towlower(3), towupper(3), locale(7)
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42GNU 1993-04-04 TOUPPER(3)