Manpage of SCANDIR

SCANDIR

Section: Linux Programmer's Manual (3)
Updated: 2016-03-15
Index
 

NAME

scandir, scandirat, 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 struct dirent **a, const struct dirent **b);int versionsort(const struct dirent **a, const struct dirent **b);#include <fcntl.h> /* Definition of AT_* constants */ #include <dirent.h>
int scandirat(int dirfd, const char *dirp,struct dirent ***namelist,
int (*filter)(const struct dirent *),int (*compar)(const struct dirent **, const struct dirent **));

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

scandir(), alphasort():

/* Since glibc 2.10: */ _POSIX_C_SOURCE >= 200809L
    || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

versionsort(): _GNU_SOURCE

scandirat(): _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 namelistwhich 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.  

scandirat()

The scandirat() function operates in exactly the same way as scandir(), except for the differences described here.

If the pathname given in dirpis relative, then it is interpreted relative to the directory referred to by the file descriptor dirfd(rather than relative to the current working directory of the calling process, as is done by scandir() for a relative pathname).

If dirpis relative and dirfdis the special value AT_FDCWD, then dirpis interpreted relative to the current working directory of the calling process (like scandir()).

If dirpis absolute, then dirfdis ignored.

See openat(2) for an explanation of the need for scandirat().  

RETURN VALUE

The scandir() function returns the number of directory entries selected. On error, -1 is returned, with errnoset to indicate the cause of the error.

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

ENOENT
The path in dirp does not exist.
ENOMEM
Insufficient memory to complete the operation.
ENOTDIR
The path in dirp is not a directory.

The following additional errors can occur for scandirat():

EBADF
dirfdis not a valid file descriptor.
ENOTDIR
dirpis a relative path and dirfdis a file descriptor referring to a file other than a directory.
 

VERSIONS

versionsort() was added to glibc in version 2.1.

scandirat() was added to glibc in version 2.15.  

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).
InterfaceAttributeValue
scandir(), scandirat() Thread safetyMT-Safe
alphasort(), versionsort() Thread safetyMT-Safe locale

 

CONFORMING TO

alphasort(), scandir(): 4.3BSD, POSIX.1-2008.

versionsort() and scandirat() are GNU extensions.  

NOTES

Since glibc 2.1, alphasort() calls strcoll(3); earlier it used strcmp(3).

Before glibc 2.10, the two arguments of alphasort() and versionsort() were typed as const void *. When alphasort() was standardized in POSIX.1-2008, the argument type was specified as the type-safe const struct dirent **,and glibc 2.10 changed the definition of alphasort() (and the nonstandard versionsort()) to match the standard.  

EXAMPLE

#define _DEFAULT_SOURCE
/* print files in current directory in reverse order */
#include <dirent.h>

int
main(void)
{
    struct dirent **namelist;
    int n;

    n = scandir(".", &namelist, NULL, 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)


 

Index

NAME
SYNOPSIS
DESCRIPTION
scandirat()
RETURN VALUE
ERRORS
VERSIONS
ATTRIBUTES
CONFORMING TO
NOTES
EXAMPLE
SEE ALSO

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Time: 22:27:57 GMT, June 20, 2016