The Open Group Base Specifications Issue 6
IEEE Std 1003.1, 2004 Edition
Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.
A newer edition of this document exists here


strcoll - string comparison using collating information


#include <string.h>

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


[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 IEEE Std 1003.1-2001 defers to the ISO C standard. [Option End]

The strcoll() function 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] The strcoll() function 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(), then check errno. [Option End]


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. [Option End]


The strcoll() function may fail if:

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

The following sections are informative.


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);


The strxfrm() and strcmp() functions should be used for sorting large lists.






strcmp(), strxfrm(), the Base Definitions volume of IEEE Std 1003.1-2001, <string.h>


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.

End of informative text.

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