STRCOLL
Section: POSIX Programmer's Manual (3P)
Updated: 2017
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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.
NAME
strcoll,
strcoll_l
--- string comparison using collating information
SYNOPSIS
#include <string.h>
int strcoll(const char *s1, const char *s2);
int strcoll_l(const char *s1, const char *s2,
locale_t locale);
DESCRIPTION
For
strcoll():
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
strcoll()
and
strcoll_l()
functions shall compare the string pointed to by
s1
to the string pointed to by
s2,
both interpreted as appropriate to the
LC_COLLATE
category of the current locale,
or of the locale represented by
locale,
respectively.
The
strcoll()
and
strcoll_l()
functions shall not change the setting of
errno
if successful.
Since no return value is reserved to indicate an error, an
application wishing to check for error situations should set
errno
to 0, then call
strcoll(),
or
strcoll_l()
then check
errno.
The behavior is undefined if the
locale
argument to
strcoll_l()
is the special locale object LC_GLOBAL_LOCALE or is not a valid locale
object handle.
RETURN VALUE
Upon successful completion,
strcoll()
shall return an integer greater than, equal to, or less than
0, according to whether the string pointed to by
s1
is greater than, equal to, or less than the string pointed to by
s2
when both are interpreted as appropriate to the current locale.
On error,
strcoll()
may set
errno,
but no return value is reserved to indicate an error.
Upon successful completion,
strcoll_l()
shall return an integer greater than, equal to, or less than 0,
according to whether the string pointed to by
s1
is greater than, equal to, or less than the string pointed to by
s2
when both are interpreted as appropriate to the locale represented by
locale.
On error,
strcoll_l()
may set
errno,
but no return value is reserved to indicate an error.
ERRORS
These functions may fail if:
- EINVAL
-
The
s1
or
s2
arguments contain characters outside the domain of the collating
sequence.
The following sections are informative.
EXAMPLES
Comparing Nodes
The following example uses an application-defined function,
node_compare(),
to compare two nodes based on an alphabetical ordering of the
string
field.
-
#include <string.h>
...
struct node { /* These are stored in the table. */
char *string;
int length;
};
...
int node_compare(const void *node1, const void *node2)
{
return strcoll(((const struct node *)node1)->string,
((const struct node *)node2)->string);
}
...
APPLICATION USAGE
The
strxfrm()
and
strcmp()
functions should be used for sorting large lists.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
alphasort(),
strcmp(),
strxfrm()
The Base Definitions volume of POSIX.1-2017,
<string.h>
COPYRIGHT
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 .