tolower
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C
Concurrency support (C11)
Null-terminated byte strings
Functions
Character manipulation
Conversions to and from numeric formats
(C99)(C99)
(C99)(C99)
(C23)(C23)(C23)
String manipulation
String examination
Memory manipulation
Miscellaneous
(C11)(C11)
Defined in header
<ctype.h>
int tolower( int ch );
Converts the given character to lowercase according to the character conversion rules defined by the currently installed C locale.
In the default "C" locale, the following uppercase letters ABCDEFGHIJKLMNOPQRSTUVWXYZ are replaced with respective lowercase letters abcdefghijklmnopqrstuvwxyz.
[edit] Parameters
ch
-
character to be converted. If the value of ch is not representable as unsigned char and does not equal EOF , the behavior is undefined.
[edit] Return value
Lowercase version of ch or unmodified ch if no lowercase version is listed in the current C locale.
[edit] Example
Run this code
#include <ctype.h> #include <limits.h> #include <locale.h> #include <stdio.h> int main(void) { // In the default locale for (unsigned char u = 0; u < UCHAR_MAX ; u++) { unsigned char l = tolower(u); if (l != u) printf ("%c%c ", u, l); } printf ("\n\n"); unsigned char c = '\xb4'; // the character Ž in ISO-8859-15 // but ́ (acute accent) in ISO-8859-1 setlocale (LC_ALL, "en_US.iso88591"); printf ("in iso8859-1, tolower('0x%x') gives 0x%x\n", c, tolower(c)); setlocale (LC_ALL, "en_US.iso885915"); printf ("in iso8859-15, tolower('0x%x') gives 0x%x\n", c, tolower(c)); }
Possible output:
Aa Bb Cc Dd Ee Ff Gg Hh Ii Jj Kk Ll Mm Nn Oo Pp Qq Rr Ss Tt Uu Vv Ww Xx Yy Zz
in iso8859-1, tolower('0xb4') gives 0xb4
in iso8859-15, tolower('0xb4') gives 0xb8[edit] References
- C23 standard (ISO/IEC 9899:2024):
- 7.4.2.1 The tolower function (p: TBD)
- C17 standard (ISO/IEC 9899:2018):
- 7.4.2.1 The tolower function (p: 147)
- C11 standard (ISO/IEC 9899:2011):
- 7.4.2.1 The tolower function (p: 203)
- C99 standard (ISO/IEC 9899:1999):
- 7.4.2.1 The tolower function (p: 184)
- C89/C90 standard (ISO/IEC 9899:1990):
- 4.3.2.1 The tolower function
[edit] See also
C++ documentation for tolower