STRCOLL(3POSIX)

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.

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 .