SCANDIR(3) - Linux man page online | Library functions

Scan a directory for matching entries.

SCANDIR(3) Linux Programmer's Manual SCANDIR(3)


scandir, scandirat, alphasort, versionsort - scan a directory for matching entries


#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


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 com‐ par(). The former sorts directory entries using strcoll(3), the latter using strver‐ scmp(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 dirp is relative, then it is interpreted relative to the direc‐ tory 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 dirp is relative and dirfd is the special value AT_FDCWD, then dirp is interpreted rel‐ ative to the current working directory of the calling process (like scandir()). If dirp is absolute, then dirfd is ignored. See openat(2) for an explanation of the need for scandirat().


The scandir() function returns the number of directory entries selected. On error, -1 is returned, with errno set 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.


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 dirfd is not a valid file descriptor. ENOTDIR dirp is a relative path and dirfd is a file descriptor referring to a file other than a directory.


versionsort() was added to glibc in version 2.1. scandirat() was added to glibc in version 2.15.


For an explanation of the terms used in this section, see attributes(7). ┌───────────────────────────┬───────────────┬────────────────┐ │Interface │ Attribute │ Value │ ├───────────────────────────┼───────────────┼────────────────┤ │scandir(), scandirat() │ Thread safety │ MT-Safe │ ├───────────────────────────┼───────────────┼────────────────┤ │alphasort(), versionsort() │ Thread safety │ MT-Safe locale │ └───────────────────────────┴───────────────┴────────────────┘


alphasort(), scandir(): 4.3BSD, POSIX.1-2008. versionsort() and scandirat() are GNU extensions.


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 speci‐ fied as the type-safe const struct dirent **, and glibc 2.10 changed the definition of alphasort() (and the nonstandard versionsort()) to match the standard.


The program below prints a list of the files in the current directory in reverse order. Program source #define _DEFAULT_SOURCE #include <dirent.h> #include <stdio.h> #include <stdlib.h> int main(void) { struct dirent **namelist; int n; n = scandir(".", &namelist, NULL, alphasort); if (n == -1) { perror("scandir"); exit(EXIT_FAILURE); } while (n--) { printf("%s\n", namelist[n]->d_name); free(namelist[n]); } free(namelist); exit(EXIT_SUCCESS); }


closedir(3), fnmatch(3), opendir(3), readdir(3), rewinddir(3), seekdir(3), strcmp(3), str‐ coll(3), strverscmp(3), telldir(3)


This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at
GNU 2017-09-15 SCANDIR(3)
This manual Reference Other manuals
scandir(3) referred by aufs(5) | closedir(3) | dirfd(3) | fnmatch(3) | open(2) | opendir(3) | qsort(3) | readdir(3) | rewinddir(3) | seekdir(3) | strverscmp(3) | telldir(3)
refer to attributes(7) | closedir(3) | feature_test_macros(7) | fnmatch(3) | malloc(3) | open(2) | opendir(3) | qsort(3) | readdir(3) | rewinddir(3) | seekdir(3) | strcmp(3) | strcoll(3) | strverscmp(3) | telldir(3)
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