The Open Group Base Specifications Issue 8
IEEE Std 1003.1-2024
Copyright © 2001-2024 The IEEE and The Open Group

NAME

strcoll, strcoll_l — string comparison using collating information

SYNOPSIS

#include <string.h>

int strcoll(const char *
s1, const char *s2);

[CX] [Option Start] int strcoll_l(const char *s1, const char *s2,
       locale_t
locale); [Option End]

DESCRIPTION

For strcoll(): [CX] [Option Start]  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.1-2024 defers to the ISO C standard. [Option End]

The strcoll() [CX] [Option Start]  and strcoll_l() [Option End]  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, [CX] [Option Start]  or of the locale represented by locale, [Option End]  respectively.

The strcoll() [CX] [Option Start]  and strcoll_l() [Option End]  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(), [CX] [Option Start]  or strcoll_l() [Option End]  then check errno.

[CX] [Option Start] 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. [Option End]

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. [CX] [Option Start]  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. [Option End]

ERRORS

These functions may fail if:

[EINVAL]
[CX] [Option Start] The s1 or s2 arguments contain characters outside the domain of the collating sequence. [Option End]

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

XBD <string.h>

CHANGE HISTORY

First released in Issue 3.

Issue 5

The DESCRIPTION is updated to indicate that errno does not change if the function is successful.

Issue 6

Extensions beyond the ISO C standard are marked.

The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:

An example is added.

Issue 7

The strcoll_l() function is added from The Open Group Technical Standard, 2006, Extended API Set Part 4.

POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0593 [283] and XSH/TC1-2008/0594 [283] are applied.

End of informative text.

 

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