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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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TOLOWER(3P) POSIX Programmer's Manual TOLOWER(3P)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
tolower, tolower_l — transliterate uppercase characters to
lowercase
#include <ctype.h>
int tolower(int c);
int tolower_l(int c, locale_t locale);
For tolower(): The functionality described on this reference page
is aligned with the ISO C standard. Any conflict between the
requirements described here and the ISO C standard is
unintentional. This volume of POSIX.1‐2017 defers to the ISO C
standard.
The tolower() and tolower_l() functions have as a domain a type
int, the value of which is representable as an unsigned char or
the value of EOF. If the argument has any other value, the
behavior is undefined. If the argument of tolower() or tolower_l()
represents an uppercase letter, and there exists a corresponding
lowercase letter as defined by character type information in the
current locale or in the locale represented by locale,
respectively (category LC_CTYPE), the result shall be the
corresponding lowercase letter. All other arguments in the domain
are returned unchanged.
The behavior is undefined if the locale argument to tolower_l() is
the special locale object LC_GLOBAL_LOCALE or is not a valid
locale object handle.
Upon successful completion, the tolower() and tolower_l()
functions shall return the lowercase letter corresponding to the
argument passed; otherwise, they shall return the argument
unchanged.
No errors are defined.
The following sections are informative.
None.
None.
None.
None.
setlocale(3p), uselocale(3p)
The Base Definitions volume of POSIX.1‐2017, Chapter 7, Locale,
ctype.h(0p), locale.h(0p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute of Electrical and Electronics Engineers,
Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard,
the original IEEE and The Open Group Standard is the referee
document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 TOLOWER(3P)
Pages that refer to this page: ctype.h(0p), setlocale(3p), _tolower(3p)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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