alphasort(3)

1SCANDIR(3)                 Linux Programmer's Manual                SCANDIR(3)
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NAME

6       scandir, alphasort, versionsort - scan a directory for matching entries
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SYNOPSIS

9       #include <dirent.h>
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11       int scandir(const char *dirp, struct dirent ***namelist,
12              int (*filter)(const struct dirent *),
13              int (*compar)(const struct dirent **, const struct dirent **));
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15       int alphasort(const void *a, const void *b);
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17       int versionsort(const void *a, const void *b);
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19   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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21       scandir(), alphasort(): _BSD_SOURCE || _SVID_SOURCE
22       versionsort(): _GNU_SOURCE
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DESCRIPTION

25       The  scandir()  function  scans the directory dirp, calling filter() on
26       each directory entry.  Entries for which filter() returns  nonzero  are
27       stored  in  strings allocated via malloc(3), sorted using qsort(3) with
28       the comparison function compar(), and collected in array namelist which
29       is  allocated  via  malloc(3).   If  filter  is  NULL,  all entries are
30       selected.
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32       The alphasort() and versionsort() functions can be used as the compari‐
33       son  function  compar().  The former sorts directory entries using str‐
34       coll(3), the latter using strverscmp(3) on the strings (*a)->d_name and
35       (*b)->d_name.
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RETURN VALUE

38       The scandir() function returns the number of directory entries selected
39       or -1 if an error occurs.
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41       The alphasort() and versionsort()  functions  return  an  integer  less
42       than,  equal  to, or greater than zero if the first argument is consid‐
43       ered to be respectively less than, equal to, or greater than  the  sec‐
44       ond.
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ERRORS

47       ENOMEM Insufficient memory to complete the operation.
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VERSIONS

50       versionsort() was added to glibc in version 2.1.
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CONFORMING TO

53       alphasort() and scandir() are specified in POSIX.1-2008, and are widely
54       available.  versionsort() is a GNU extension.
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56       The functions scandir() and alphasort() are from 4.3BSD, and have  been
57       available  under  Linux since libc4.  Libc4 and libc5 use the more pre‐
58       cise prototype
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60           int alphasort(const struct dirent ** a,
61                         const struct dirent **b);
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63       but glibc 2.0 returns to the imprecise BSD prototype.
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65       The function versionsort() is a GNU extension,  available  since  glibc
66       2.1.
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68       Since  glibc  2.1,  alphasort()  calls strcoll(3); earlier it used str‐
69       cmp(3).
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EXAMPLE

72       #define _SVID_SOURCE
73       /* print files in current directory in reverse order */
74       #include <dirent.h>
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76       int
77       main(void)
78       {
79           struct dirent **namelist;
80           int n;
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82           n = scandir(".", &namelist, 0, alphasort);
83           if (n < 0)
84               perror("scandir");
85           else {
86               while (n--) {
87                   printf("%s\n", namelist[n]->d_name);
88                   free(namelist[n]);
89               }
90               free(namelist);
91           }
92       }
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COLOPHON

99       This  page  is  part of release 3.25 of the Linux man-pages project.  A
100       description of the project, and information about reporting  bugs,  can
101       be found at http://www.kernel.org/doc/man-pages/.
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105GNU                               2009-02-10                        SCANDIR(3)