FTW(3)                 FreeBSD Library Functions Manual                 FTW(3)

NAME
     ftw, nftw - traverse (walk) a file tree

SYNOPSIS
     #include <ftw.h>

     int
     ftw(const char *path, int (*fn)(const char *, const struct stat *, int),)(const char *, const struct stat *, int),
         int maxfds);

     int
     nftw(const char *path,
         int (*fn)(const char *, const struct stat *, int, struct FTW *),)(const char *, const struct stat *, int, struct FTW *),
         int maxfds, int flags);

DESCRIPTION
     The ftw() and nftw() functions traverse (walk) the directory hierarchy
     rooted in path.  For each object in the hierarchy, these functions call
     the function pointed to by fn.  The ftw() function passes this function a
     pointer to a NUL-terminated string containing the name of the object, a
     pointer to a stat structure corresponding to the object, and an integer
     flag.  The nftw() function passes the aforementioned arguments plus a
     pointer to a FTW structure as defined by <ftw.h> (shown below):

     struct FTW {
         int base;   /* offset of basename into pathname */
         int level;  /* directory depth relative to starting point */
     };

     Possible values for the flag passed to fn are:

     FTW_F        A regular file.

     FTW_D        A directory being visited in pre-order.

     FTW_DNR      A directory which cannot be read.  The directory will not be
                  descended into.

     FTW_DP       A directory being visited in post-order (nftw() only).

     FTW_NS       A file for which no stat(2) information was available.  The
                  contents of the stat structure are undefined.

     FTW_SL       A symbolic link.

     FTW_SLN      A symbolic link with a non-existent target (nftw() only).

     The ftw() function traverses the tree in pre-order.  That is, it
     processes the directory before the directory's contents.

     The maxfds argument specifies the maximum number of file descriptors to
     keep open while traversing the tree.  It has no effect in this
     implementation.

     The nftw() function has an additional flags argument with the following
     possible values:

     FTW_PHYS       Physical walk, do not follow symbolic links.

     FTW_MOUNT      The walk will not cross a mount point.

     FTW_DEPTH      Process directories in post-order.  Contents of a
                    directory are visited before the directory itself.  By
                    default, nftw() traverses the tree in pre-order.

     FTW_CHDIR      Change to a directory before reading it.  By default,
                    nftw() will change its starting directory.  The current
                    working directory will be restored to its original value
                    before nftw() returns.

RETURN VALUES
     If the tree was traversed successfully, the ftw() and nftw() functions
     return 0.  If the function pointed to by fn returns a non-zero value,
     ftw() and nftw() will stop processing the tree and return the value from
     fn.  Both functions return -1 if an error is detected.

EXAMPLES
     Following there is an example that shows how nftw can be used.  It
     traverses the file tree starting at the directory pointed by the only
     program argument and shows the complete path and a brief indicator about
     the file type.

       #include <ftw.h>
       #include <stdio.h>
       #include <sysexits.h>

       int
       nftw_callback(const char *path, const struct stat *sb, int typeflag, struct FTW *ftw)
       {
               char type;

               switch(typeflag) {
               case FTW_F:
                       type = 'F';
                       break;
               case FTW_D:
                       type = 'D';
                       break;
               case FTW_DNR:
                       type = '-';
                       break;
               case FTW_DP:
                       type = 'd';
                       break;
               case FTW_NS:
                       type = 'X';
                       break;
               case FTW_SL:
                       type = 'S';
                       break;
               case FTW_SLN:
                       type = 's';
                       break;
               default:
                       type = '?';
                       break;
               }

               printf("[%c] %s\n", type, path);

               return (0);
       }

       int
       main(int argc, char **argv)
       {

               if (argc != 2) {
                       printf("Usage %s <directory>\n", argv[0]);
                       return (EX_USAGE);
               } else
                       return (nftw(argv[1], nftw_callback, /* UNUSED */ 1, 0));
       }

ERRORS
     The ftw() and nftw() functions may fail and set errno for any of the
     errors specified for the library functions close(2), open(2), stat(2),
     malloc(3), opendir(3) and readdir(3).  If the FTW_CHDIR flag is set, the
     nftw() function may fail and set errno for any of the errors specified
     for chdir(2).  In addition, either function may fail and set errno as
     follows:

     [EINVAL]           The maxfds argument is less than 1.

SEE ALSO
     chdir(2), close(2), open(2), stat(2), fts(3), malloc(3), opendir(3),
     readdir(3)

STANDARDS
     The ftw() and nftw() functions conform to IEEE Std 1003.1-2001
     ("POSIX.1").

HISTORY
     These functions first appeared in AT&T System V Release 3 UNIX.  Their
     first FreeBSD appearance was in FreeBSD 5.3.

BUGS
     The maxfds argument is currently ignored.

FreeBSD 13.1-RELEASE-p6         March 12, 2020         FreeBSD 13.1-RELEASE-p6