'\" t .\" Copyright (c) 1993 Michael Haardt (michael@moria.de) .\" and copyright (c) 1999 Andries Brouwer (aeb@cwi.nl) .\" and copyright (c) 2006 Justin Pryzby .\" and copyright (c) 2006 Michael Kerrisk .\" .\" SPDX-License-Identifier: GPL-2.0-or-later .\" .\" Modified Sun Jul 25 11:02:22 1993 by Rik Faith (faith@cs.unc.edu) .\" 2006-05-24, Justin Pryzby .\" document FTW_ACTIONRETVAL; include .SH RETURN VALUE; .\" 2006-05-24, Justin Pryzby and .\" Michael Kerrisk .\" reorganized and rewrote much of the page .\" 2006-05-24, Michael Kerrisk .\" Added an example program. .\" .TH ftw 3 2023-03-30 "Linux man-pages 6.04" .SH NAME ftw, nftw \- file tree walk .SH LIBRARY Standard C library .RI ( libc ", " \-lc ) .SH SYNOPSIS .nf .B #include .PP .BI "int nftw(const char *" dirpath , .BI " int (*" fn ")(const char *" fpath ", const struct stat *" sb , .BI " int " typeflag ", struct FTW *" ftwbuf ), .BI " int " nopenfd ", int " flags ); .PP .B [[deprecated]] .BI "int ftw(const char *" dirpath , .BI " int (*" fn ")(const char *" fpath ", const struct stat *" sb , .BI " int " typeflag ), .BI " int " nopenfd ); .fi .PP .RS -4 Feature Test Macro Requirements for glibc (see .BR feature_test_macros (7)): .RE .PP .BR nftw (): .nf _XOPEN_SOURCE >= 500 .fi .SH DESCRIPTION .BR nftw () walks through the directory tree that is located under the directory \fIdirpath\fP, and calls \fIfn\fP() once for each entry in the tree. By default, directories are handled before the files and subdirectories they contain (preorder traversal). .PP To avoid using up all of the calling process's file descriptors, \fInopenfd\fP specifies the maximum number of directories that .BR nftw () will hold open simultaneously. When the search depth exceeds this, .BR nftw () will become slower because directories have to be closed and reopened. .BR nftw () uses at most one file descriptor for each level in the directory tree. .PP For each entry found in the tree, .BR nftw () calls \fIfn\fP() with four arguments: .IR fpath , .IR sb , .IR typeflag , and .IR ftwbuf . .I fpath is the pathname of the entry, and is expressed either as a pathname relative to the calling process's current working directory at the time of the call to .BR nftw (), if .I dirpath was expressed as a relative pathname, or as an absolute pathname, if .I dirpath was expressed as an absolute pathname. .I sb is a pointer to the .I stat structure returned by a call to .BR stat (2) for .IR fpath . .PP The .I typeflag argument passed to .IR fn () is an integer that has one of the following values: .TP .B FTW_F .I fpath is a regular file. .TP .B FTW_D .I fpath is a directory. .TP .B FTW_DNR .I fpath is a directory which can't be read. .TP .B FTW_DP .I fpath is a directory, and \fBFTW_DEPTH\fP was specified in \fIflags\fP. (If .B FTW_DEPTH was not specified in .IR flags , then directories will always be visited with .I typeflag set to .BR FTW_D .) All of the files and subdirectories within \fIfpath\fP have been processed. .TP .B FTW_NS The .BR stat (2) call failed on .IR fpath , which is not a symbolic link. The probable cause for this is that the caller had read permission on the parent directory, so that the filename .I fpath could be seen, but did not have execute permission, so that the file could not be reached for .BR stat (2). The contents of the buffer pointed to by .I sb are undefined. .TP .B FTW_SL .I fpath is a symbolic link, and \fBFTW_PHYS\fP was set in \fIflags\fP. .\" To obtain the definition of this constant from .\" .IR , .\" either .\" .B _BSD_SOURCE .\" must be defined, or .\" .BR _XOPEN_SOURCE .\" must be defined with a value of 500 or more. .TP .B FTW_SLN .I fpath is a symbolic link pointing to a nonexistent file. (This occurs only if \fBFTW_PHYS\fP is not set.) In this case the .I sb argument passed to .IR fn () contains information returned by performing .BR lstat (2) on the "dangling" symbolic link. (But see BUGS.) .PP The fourth argument .RI ( ftwbuf ) that .BR nftw () supplies when calling \fIfn\fP() is a pointer to a structure of type \fIFTW\fP: .PP .in +4n .EX struct FTW { int base; int level; }; .EE .in .PP .I base is the offset of the filename (i.e., basename component) in the pathname given in .IR fpath . .I level is the depth of .I fpath in the directory tree, relative to the root of the tree .RI ( dirpath , which has depth 0). .PP To stop the tree walk, \fIfn\fP() returns a nonzero value; this value will become the return value of .BR nftw (). As long as \fIfn\fP() returns 0, .BR nftw () will continue either until it has traversed the entire tree, in which case it will return zero, or until it encounters an error (such as a .BR malloc (3) failure), in which case it will return \-1. .PP Because .BR nftw () uses dynamic data structures, the only safe way to exit out of a tree walk is to return a nonzero value from \fIfn\fP(). To allow a signal to terminate the walk without causing a memory leak, have the handler set a global flag that is checked by \fIfn\fP(). \fIDon't\fP use .BR longjmp (3) unless the program is going to terminate. .PP The \fIflags\fP argument of .BR nftw () is formed by ORing zero or more of the following flags: .TP .BR FTW_ACTIONRETVAL " (since glibc 2.3.3)" If this glibc-specific flag is set, then .BR nftw () handles the return value from .IR fn () differently. .IR fn () should return one of the following values: .RS .TP .B FTW_CONTINUE Instructs .BR nftw () to continue normally. .TP .B FTW_SKIP_SIBLINGS If \fIfn\fP() returns this value, then siblings of the current entry will be skipped, and processing continues in the parent. .\" If \fBFTW_DEPTH\fP .\" is set, the entry's parent directory is processed next (with .\" \fIflag\fP set to \fBFTW_DP\fP). .TP .B FTW_SKIP_SUBTREE If \fIfn\fP() is called with an entry that is a directory (\fItypeflag\fP is \fBFTW_D\fP), this return value will prevent objects within that directory from being passed as arguments to \fIfn\fP(). .BR nftw () continues processing with the next sibling of the directory. .TP .B FTW_STOP Causes .BR nftw () to return immediately with the return value \fBFTW_STOP\fP. .PP Other return values could be associated with new actions in the future; \fIfn\fP() should not return values other than those listed above. .PP The feature test macro .B _GNU_SOURCE must be defined (before including .I any header files) in order to obtain the definition of \fBFTW_ACTIONRETVAL\fP from \fI\fP. .RE .TP .B FTW_CHDIR If set, do a .BR chdir (2) to each directory before handling its contents. This is useful if the program needs to perform some action in the directory in which \fIfpath\fP resides. (Specifying this flag has no effect on the pathname that is passed in the .I fpath argument of .IR fn .) .TP .B FTW_DEPTH If set, do a post-order traversal, that is, call \fIfn\fP() for the directory itself \fIafter\fP handling the contents of the directory and its subdirectories. (By default, each directory is handled \fIbefore\fP its contents.) .TP .B FTW_MOUNT If set, stay within the same filesystem (i.e., do not cross mount points). .TP .B FTW_PHYS If set, do not follow symbolic links. (This is what you want.) If not set, symbolic links are followed, but no file is reported twice. .IP If \fBFTW_PHYS\fP is not set, but \fBFTW_DEPTH\fP is set, then the function .IR fn () is never called for a directory that would be a descendant of itself. .SS ftw() .BR ftw () is an older function that offers a subset of the functionality of .BR nftw (). The notable differences are as follows: .IP \[bu] 3 .BR ftw () has no .I flags argument. It behaves the same as when .BR nftw () is called with .I flags specified as zero. .IP \[bu] The callback function, .IR fn (), is not supplied with a fourth argument. .IP \[bu] The range of values that is passed via the .I typeflag argument supplied to .IR fn () is smaller: just .BR FTW_F , .BR FTW_D , .BR FTW_DNR , .BR FTW_NS , and (possibly) .BR FTW_SL . .SH RETURN VALUE These functions return 0 on success, and \-1 if an error occurs. .PP If \fIfn\fP() returns nonzero, then the tree walk is terminated and the value returned by \fIfn\fP() is returned as the result of .BR ftw () or .BR nftw (). .PP If .BR nftw () is called with the \fBFTW_ACTIONRETVAL\fP flag, then the only nonzero value that should be used by \fIfn\fP() to terminate the tree walk is \fBFTW_STOP\fP, and that value is returned as the result of .BR nftw (). .SH ATTRIBUTES For an explanation of the terms used in this section, see .BR attributes (7). .ad l .nh .TS allbox; lbx lb lb l l l. Interface Attribute Value T{ .BR nftw () T} Thread safety MT-Safe cwd T{ .BR ftw () T} Thread safety MT-Safe .TE .hy .ad .sp 1 .SH VERSIONS In some implementations (e.g., glibc), .BR ftw () will never use \fBFTW_SL\fP; on other systems \fBFTW_SL\fP occurs only for symbolic links that do not point to an existing file; and again on other systems .BR ftw () will use \fBFTW_SL\fP for each symbolic link. If .I fpath is a symbolic link and .BR stat (2) failed, POSIX.1-2008 states that it is undefined whether \fBFTW_NS\fP or \fBFTW_SL\fP is passed in .IR typeflag . For predictable results, use .BR nftw (). .SH STANDARDS POSIX.1-2008. .SH HISTORY .TP .BR ftw () POSIX.1-2001, SVr4, SUSv1. POSIX.1-2008 marks it as obsolete. .TP .BR nftw () glibc 2.1. POSIX.1-2001, SUSv1. .TP .B FTW_SL POSIX.1-2001, SUSv1. .SH NOTES POSIX.1-2008 notes that the results are unspecified if .I fn does not preserve the current working directory. .SH BUGS According to POSIX.1-2008, when the .I typeflag argument passed to .IR fn () contains .BR FTW_SLN , the buffer pointed to by .I sb should contain information about the dangling symbolic link (obtained by calling .BR lstat (2) on the link). Early glibc versions correctly followed the POSIX specification on this point. However, as a result of a regression introduced in glibc 2.4, the contents of the buffer pointed to by .I sb were undefined when .B FTW_SLN is passed in .IR typeflag . (More precisely, the contents of the buffer were left unchanged in this case.) This regression was eventually fixed in glibc 2.30, .\" https://bugzilla.redhat.com/show_bug.cgi?id=1422736 .\" http://austingroupbugs.net/view.php?id=1121 .\" glibc commit 6ba205b2c35e3e024c8c12d2ee1b73363e84da87 .\" https://sourceware.org/bugzilla/show_bug.cgi?id=23501 so that the glibc implementation (once more) follows the POSIX specification. .SH EXAMPLES The following program traverses the directory tree under the path named in its first command-line argument, or under the current directory if no argument is supplied. It displays various information about each file. The second command-line argument can be used to specify characters that control the value assigned to the \fIflags\fP argument when calling .BR nftw (). .SS Program source \& .\" SRC BEGIN (ftw.c) .EX #define _XOPEN_SOURCE 500 #include #include #include #include #include static int display_info(const char *fpath, const struct stat *sb, int tflag, struct FTW *ftwbuf) { printf("%\-3s %2d ", (tflag == FTW_D) ? "d" : (tflag == FTW_DNR) ? "dnr" : (tflag == FTW_DP) ? "dp" : (tflag == FTW_F) ? "f" : (tflag == FTW_NS) ? "ns" : (tflag == FTW_SL) ? "sl" : (tflag == FTW_SLN) ? "sln" : "???", ftwbuf\->level); if (tflag == FTW_NS) printf("\-\-\-\-\-\-\-"); else printf("%7jd", (intmax_t) sb\->st_size); printf(" %\-40s %d %s\en", fpath, ftwbuf\->base, fpath + ftwbuf\->base); return 0; /* To tell nftw() to continue */ } int main(int argc, char *argv[]) { int flags = 0; if (argc > 2 && strchr(argv[2], \[aq]d\[aq]) != NULL) flags |= FTW_DEPTH; if (argc > 2 && strchr(argv[2], \[aq]p\[aq]) != NULL) flags |= FTW_PHYS; if (nftw((argc < 2) ? "." : argv[1], display_info, 20, flags) == \-1) { perror("nftw"); exit(EXIT_FAILURE); } exit(EXIT_SUCCESS); } .EE .\" SRC END .SH SEE ALSO .BR stat (2), .BR fts (3), .BR readdir (3)