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SCANDIR
Section: Linux Programmer's Manual (3)
Updated: 2009-02-10
Index
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NAME
scandir, alphasort, versionsort - scan a directory for matching entries
SYNOPSIS
#include <dirent.h>
int scandir(const char *dirp, struct dirent ***namelist,
- int (*filter)(const struct dirent *),
int (*compar)(const struct dirent **, const struct dirent **));
int alphasort(const void *a, const void *b);
int versionsort(const void *a, const void *b);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
scandir(),
alphasort():
_BSD_SOURCE || _SVID_SOURCE
versionsort():
_GNU_SOURCE
DESCRIPTION
The
scandir()
function scans the directory dirp, calling
filter() on each directory entry.
Entries for which
filter() returns nonzero are stored in strings allocated via
malloc(3),
sorted using
qsort(3)
with the comparison
function compar(), and collected in array namelist
which is allocated via
malloc(3).
If filter is NULL, all entries are selected.
The
alphasort()
and
versionsort()
functions can be used as the comparison function
compar().
The former sorts directory entries using
strcoll(3),
the latter using
strverscmp(3)
on the strings (*a)->d_name and (*b)->d_name.
RETURN VALUE
The
scandir()
function returns the number of directory entries
selected or -1 if an error occurs.
The
alphasort()
and
versionsort()
functions return an integer less than, equal to,
or greater than zero if the first argument is considered to be
respectively less than, equal to, or greater than the second.
ERRORS
- ENOMEM
-
Insufficient memory to complete the operation.
VERSIONS
versionsort()
was added to glibc in version 2.1.
CONFORMING TO
alphasort()
and
scandir()
are specified in POSIX.1-2008, and are widely available.
versionsort()
is a GNU extension.
The functions
scandir()
and
alphasort()
are from 4.3BSD, and have been available under Linux since libc4.
Libc4 and libc5 use the more precise prototype
int alphasort(const struct dirent ** a,
const struct dirent **b);
but glibc 2.0 returns to the imprecise BSD prototype.
The function
versionsort()
is a GNU extension, available since glibc 2.1.
Since glibc 2.1,
alphasort()
calls
strcoll(3);
earlier it used
strcmp(3).
EXAMPLE
#define _SVID_SOURCE
/* print files in current directory in reverse order */
#include <dirent.h>
int
main(void)
{
struct dirent **namelist;
int n;
n = scandir(".", &namelist, 0, alphasort);
if (n < 0)
perror("scandir");
else {
while (n--) {
printf("%s\n", namelist[n]->d_name);
free(namelist[n]);
}
free(namelist);
}
}
SEE ALSO
closedir(3),
fnmatch(3),
opendir(3),
readdir(3),
rewinddir(3),
seekdir(3),
strcmp(3),
strcoll(3),
strverscmp(3),
telldir(3)
COLOPHON
This page is part of release 3.27 of the Linux
man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- VERSIONS
-
- CONFORMING TO
-
- EXAMPLE
-
- SEE ALSO
-
- COLOPHON
-
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