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.TH ALPHASORT "3P" 2013 "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

alphasort, scandir

\(em scan a directory

.SH SYNOPSIS

.LP

.nf

#include <dirent.h>

.P

int alphasort(const struct dirent **\fId1\fP, const struct dirent **\fId2\fP);

int scandir(const char *\fIdir\fP, struct dirent ***\fInamelist\fP,

    int (*\fIsel\fP)(const struct dirent *),

    int (*\fIcompar\fP)(const struct dirent **, const struct dirent **));

.fi

.SH DESCRIPTION

The

\fIalphasort\fR()

function can be used as the comparison function for the

\fIscandir\fR()

function to sort the directory entries,

.IR d1

and

.IR d2 ,

into alphabetical order. Sorting happens as if by calling the

\fIstrcoll\fR()

function on the

.IR d_name

element of the

.BR dirent

structures passed as the two parameters. If the

\fIstrcoll\fR()

function fails, the return value of

\fIalphasort\fR()

is unspecified.

.P

The

\fIalphasort\fR()

function shall not change the setting of

.IR errno

if successful. 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

\fIalphasort\fR(),

then check

.IR errno .

.P

The

\fIscandir\fR()

function shall scan the directory

.IR dir ,

calling the function referenced by

.IR sel

on each directory entry. Entries for which the function referenced by

.IR sel

returns non-zero shall be stored in strings allocated as if by

a call to

\fImalloc\fR(),

and sorted as if by a call to

\fIqsort\fR()

with the comparison function

.IR compar ,

except that

.IR compar

need not provide total ordering. The strings are collected in

array

.IR namelist

which shall be allocated as if by a call to

\fImalloc\fR().

If

.IR sel

is a null pointer, all entries shall be selected.

If the comparison function

.IR compar

does not provide total ordering, the order in which the directory

entries are stored is unspecified.

.SH "RETURN VALUE"

Upon successful completion, the

\fIalphasort\fR()

function shall return an integer greater than, equal to, or less than 0,

according to whether the name of the directory entry pointed to by

.IR d1

is lexically greater than, equal to, or less than the directory pointed

to by

.IR d2

when both are interpreted as appropriate to the current locale. There

is no return value reserved to indicate an error.

.P

Upon successful completion, the

\fIscandir\fR()

function shall return the number of entries in the array and a pointer

to the array through the parameter

.IR namelist .

Otherwise, the

\fIscandir\fR()

function shall return \(mi1.

.SH ERRORS

The

\fIscandir\fR()

function shall fail if:

.TP

.BR EACCES

Search permission is denied for the component of the path prefix of

.IR dir

or read permission is denied for

.IR dir .

.TP

.BR ELOOP

A loop exists in symbolic links encountered during resolution of the

.IR dir

argument.

.TP

.BR ENAMETOOLONG

.br

The length of a component of a pathname is longer than

{NAME_MAX}.

.TP

.BR ENOENT

A component of

.IR dir

does not name an existing directory or

.IR dir

is an empty string.

.TP

.BR ENOMEM

Insufficient storage space is available.

.TP

.BR ENOTDIR

A component of

.IR dir

names an existing file that is neither a directory nor a symbolic link

to a directory.

.TP

.BR EOVERFLOW

One of the values to be returned or passed to a callback function cannot

be represented correctly.

.P

The

\fIscandir\fR()

function may fail if:

.TP

.BR ELOOP

More than

{SYMLOOP_MAX}

symbolic links were encountered during resolution of the

.IR dir

argument.

.TP

.BR EMFILE

All file descriptors available to the process are currently open.

.TP

.BR ENAMETOOLONG

.br

The length of a pathname exceeds

{PATH_MAX},

or pathname resolution of a symbolic link produced an intermediate

result with a length that exceeds

{PATH_MAX}.

.TP

.BR ENFILE

Too many files are currently open in the system.

.LP

.IR "The following sections are informative."

.SH EXAMPLES

An example to print the files in the current directory:

.sp

.RS 4

.nf

\fB

#include <dirent.h>

#include <stdio.h>

#include <stdlib.h>

\&...

struct dirent **namelist;

int i,n;

.P

    n = scandir(".", &namelist, 0, alphasort);

    if (n < 0)

        perror("scandir");

    else {

        for (i = 0; i < n; i++) {

            printf("%s\en", namelist[i]->d_name);

            free(namelist[i]);

            }

        }

    free(namelist);

\&...

.fi \fR

.P

.RE

.SH "APPLICATION USAGE"

If

.IR dir

contains filenames that do not form character strings, or which contain

characters outside the domain of the collating sequence of the current

locale, the

\fIalphasort\fR()

function need not provide a total ordering. This condition is not possible

if all filenames within the directory consist only of characters from

the portable filename character set.

.P

The

\fIscandir\fR()

function may allocate dynamic storage during its operation. If

\fIscandir\fR()

is forcibly terminated, such as by

\fIlongjmp\fR()

or

\fIsiglongjmp\fR()

being executed by the function pointed to by

.IR sel

or

.IR compar ,

or by an interrupt routine,

\fIscandir\fR()

does not have a chance to free that storage, so it remains permanently

allocated. A safe way to handle interrupts is to store the fact that

an interrupt has occurred, then wait until

\fIscandir\fR()

returns to act on the interrupt.

.P

For functions that allocate memory as if by

\fImalloc\fR(),

the application should release such memory when it is no longer

required by a call to

\fIfree\fR().

For

\fIscandir\fR(),

this is

.IR namelist

(including all of the individual strings in

.IR namelist ).

.SH RATIONALE

None.

.SH "FUTURE DIRECTIONS"

None.

.SH "SEE ALSO"

.IR "\fIqsort\fR\^(\|)",

.IR "\fIstrcoll\fR\^(\|)"

.P

The Base Definitions volume of POSIX.1\(hy2008,

.IR "\fB<dirent.h>\fP"

.SH COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form

from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology

-- Portable Operating System Interface (POSIX), The Open Group Base

Specifications Issue 7, Copyright (C) 2013 by the Institute of

Electrical and Electronics Engineers, Inc and The Open Group.

(This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/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 .