1FTW(3P)                    POSIX Programmer's Manual                   FTW(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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11

NAME

13       ftw — traverse (walk) a file tree
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SYNOPSIS

16       #include <ftw.h>
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18       int ftw(const char *path, int (*fn)(const char *,
19           const struct stat *ptr, int flag), int ndirs);
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DESCRIPTION

22       The ftw() function shall recursively descend  the  directory  hierarchy
23       rooted in path.  For each object in the hierarchy, ftw() shall call the
24       function pointed to by fn, passing it a pointer  to  a  null-terminated
25       character string containing the name of the object, a pointer to a stat
26       structure containing information about the  object,  filled  in  as  if
27       stat() or lstat() had been called to retrieve the information. Possible
28       values of the integer, defined in the <ftw.h> header, are:
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30       FTW_D     For a directory.
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32       FTW_DNR   For a directory that cannot be read.
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34       FTW_F     For a non-directory file.
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36       FTW_SL    For a symbolic link (but see also FTW_NS below).
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38       FTW_NS    For an object other than a  symbolic  link  on  which  stat()
39                 could  not  successfully be executed. If the object is a sym‐
40                 bolic link and stat() failed, it is unspecified whether ftw()
41                 passes FTW_SL or FTW_NS to the user-supplied function.
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43       If  the  integer is FTW_DNR, descendants of that directory shall not be
44       processed. If the integer is FTW_NS, the stat structure contains  unde‐
45       fined  values.  An  example  of an object that would cause FTW_NS to be
46       passed to the function pointed to by fn would be a file in a  directory
47       with read but without execute (search) permission.
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49       The  ftw()  function shall visit a directory before visiting any of its
50       descendants.
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52       The ftw() function shall use at most one file descriptor for each level
53       in the tree.
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55       The argument ndirs should be in the range [1,{OPEN_MAX}].
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57       The  tree  traversal shall continue until either the tree is exhausted,
58       an invocation of fn returns a non-zero value, or some error, other than
59       [EACCES], is detected within ftw().
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61       The  ndirs  argument  shall  specify  the  maximum  number of directory
62       streams or file descriptors or both available for use  by  ftw()  while
63       traversing  the  tree.  When ftw() returns it shall close any directory
64       streams and file descriptors it uses not counting  any  opened  by  the
65       application-supplied fn function.
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67       The  results  are  unspecified  if the application-supplied fn function
68       does not preserve the current working directory.
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70       The ftw() function need not be thread-safe.
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RETURN VALUE

73       If the tree is exhausted, ftw() shall return 0. If the function pointed
74       to  by fn returns a non-zero value, ftw() shall stop its tree traversal
75       and return whatever value was returned by the function  pointed  to  by
76       fn.   If  ftw()  detects  an error, it shall return −1 and set errno to
77       indicate the error.
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79       If ftw() encounters an error  other  than  [EACCES]  (see  FTW_DNR  and
80       FTW_NS  above), it shall return −1 and set errno to indicate the error.
81       The external variable errno may contain any error value that is  possi‐
82       ble  when  a  directory  is opened or when one of the stat functions is
83       executed on a directory or file.
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ERRORS

86       The ftw() function shall fail if:
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88       EACCES Search permission is denied for any component of  path  or  read
89              permission is denied for path.
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91       ELOOP  A loop exists in symbolic links encountered during resolution of
92              the path argument.
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94       ENAMETOOLONG
95              The  length  of  a  component  of  a  pathname  is  longer  than
96              {NAME_MAX}.
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98       ENOENT A component of path does not name an existing file or path is an
99              empty string.
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101       ENOTDIR
102              A component of path names an existing file  that  is  neither  a
103              directory nor a symbolic link to a directory.
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105       EOVERFLOW
106              A field in the stat structure cannot be represented correctly in
107              the current programming environment for one or more files  found
108              in the file hierarchy.
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110       The ftw() function may fail if:
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112       EINVAL The value of the ndirs argument is invalid.
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114       ELOOP  More  than  {SYMLOOP_MAX} symbolic links were encountered during
115              resolution of the path argument.
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117       ENAMETOOLONG
118              The length of a pathname exceeds {PATH_MAX}, or pathname resolu‐
119              tion  of  a symbolic link produced an intermediate result with a
120              length that exceeds {PATH_MAX}.
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122       In addition, if the function pointed to by fn encounters system errors,
123       errno may be set accordingly.
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125       The following sections are informative.
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EXAMPLES

128   Walking a Directory Structure
129       The  following  example  walks the current directory structure, calling
130       the fn function for every  directory  entry,  using  at  most  10  file
131       descriptors:
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133           #include <ftw.h>
134           ...
135           if (ftw(".", fn, 10) != 0) {
136               perror("ftw"); exit(2);
137           }
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APPLICATION USAGE

140       The  ftw()  function may allocate dynamic storage during its operation.
141       If ftw() is forcibly terminated, such as by longjmp()  or  siglongjmp()
142       being  executed  by  the function pointed to by fn or an interrupt rou‐
143       tine, ftw() does not have a chance to free that storage, so it  remains
144       permanently  allocated. A safe way to handle interrupts is to store the
145       fact that an interrupt has occurred, and arrange to have  the  function
146       pointed to by fn return a non-zero value at its next invocation.
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148       Applications  should use the nftw() function instead of the obsolescent
149       ftw() function.
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RATIONALE

152       None.
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FUTURE DIRECTIONS

155       The ftw() function may be removed in a future version.
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SEE ALSO

158       fdopendir(), fstatat(), longjmp(), nftw(), siglongjmp()
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160       The Base Definitions volume of POSIX.1‐2008, <ftw.h>, <sys_stat.h>
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163       Portions of this text are reprinted and reproduced in  electronic  form
164       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
165       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
166       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
167       cal and Electronics Engineers,  Inc  and  The  Open  Group.   (This  is
168       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) In the
169       event of any discrepancy between this version and the original IEEE and
170       The  Open Group Standard, the original IEEE and The Open Group Standard
171       is the referee document. The original Standard can be  obtained  online
172       at http://www.unix.org/online.html .
173
174       Any  typographical  or  formatting  errors that appear in this page are
175       most likely to have been introduced during the conversion of the source
176       files  to  man page format. To report such errors, see https://www.ker
177       nel.org/doc/man-pages/reporting_bugs.html .
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181IEEE/The Open Group                  2013                              FTW(3P)
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