'\" et
.TH STRCOLL "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH PROLOG
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.
.\"
.SH NAME
strcoll,
strcoll_l
\(em string comparison using collating information
.SH SYNOPSIS
.LP
.nf
#include <string.h>
.P
int strcoll(const char *\fIs1\fP, const char *\fIs2\fP);
int strcoll_l(const char *\fIs1\fP, const char *\fIs2\fP,
    locale_t \fIlocale\fP);
.fi
.SH DESCRIPTION
For
\fIstrcoll\fR():
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\(hy2017 defers to the ISO\ C standard.
.P
The
\fIstrcoll\fR()
and
\fIstrcoll_l\fR()
functions shall compare the string pointed to by
.IR s1
to the string pointed to by
.IR s2 ,
both interpreted as appropriate to the
.IR LC_COLLATE
category of the current locale,
or of the locale represented by
.IR locale ,
respectively.
.P
The
\fIstrcoll\fR()
and
\fIstrcoll_l\fR()
functions shall not change the setting of
.IR errno
if successful.
.P
Since no return value is reserved to indicate an error, an
application wishing to check for error situations should set
.IR errno
to 0, then call
\fIstrcoll\fR(),
or
\fIstrcoll_l\fR()
then check
.IR errno .
.P
The behavior is undefined if the
.IR locale
argument to
\fIstrcoll_l\fR()
is the special locale object LC_GLOBAL_LOCALE or is not a valid locale
object handle.
.SH "RETURN VALUE"
Upon successful completion,
\fIstrcoll\fR()
shall return an integer greater than, equal to, or less than
0, according to whether the string pointed to by
.IR s1
is greater than, equal to, or less than the string pointed to by
.IR s2
when both are interpreted as appropriate to the current locale.
On error,
\fIstrcoll\fR()
may set
.IR errno ,
but no return value is reserved to indicate an error.
.P
Upon successful completion,
\fIstrcoll_l\fR()
shall return an integer greater than, equal to, or less than 0,
according to whether the string pointed to by
.IR s1
is greater than, equal to, or less than the string pointed to by
.IR s2
when both are interpreted as appropriate to the locale represented by
.IR locale .
On error,
\fIstrcoll_l\fR()
may set
.IR errno ,
but no return value is reserved to indicate an error.
.SH ERRORS
These functions may fail if:
.TP
.BR EINVAL
The
.IR s1
or
.IR s2
arguments contain characters outside the domain of the collating
sequence.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
.SS "Comparing Nodes"
.P
The following example uses an application-defined function,
\fInode_compare\fR(),
to compare two nodes based on an alphabetical ordering of the
.IR string
field.
.sp
.RS 4
.nf

#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);
}
\&...
.fi
.P
.RE
.SH "APPLICATION USAGE"
The
\fIstrxfrm\fR()
and
\fIstrcmp\fR()
functions should be used for sorting large lists.
.SH RATIONALE
None.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "\fIalphasort\fR\^(\|)",
.IR "\fIstrcmp\fR\^(\|)",
.IR "\fIstrxfrm\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "\fB<string.h>\fP"
.\"
.SH 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 .
.PP
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 .