ftw.3p (7043B)
- '\" et
- .TH FTW "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
- .\"
- .SH PROLOG
- This manual page is part of the POSIX Programmer's Manual.
- The Linux implementation of this interface may differ (consult
- the corresponding Linux manual page for details of Linux behavior),
- or the interface may not be implemented on Linux.
- .\"
- .SH NAME
- ftw
- \(em traverse (walk) a file tree
- .SH SYNOPSIS
- .LP
- .nf
- #include <ftw.h>
- .P
- int ftw(const char *\fIpath\fP, int (*\fIfn\fP)(const char *,
- const struct stat *\fIptr\fP, int \fIflag\fP), int \fIndirs\fP);
- .fi
- .SH DESCRIPTION
- The
- \fIftw\fR()
- function shall recursively descend the directory hierarchy rooted in
- .IR path .
- For each object in the hierarchy,
- \fIftw\fR()
- shall call the function pointed to by
- .IR fn ,
- passing it a pointer to a null-terminated character string containing
- the name of the object, a pointer to a
- .BR stat
- structure containing information about the object, filled in as if
- \fIstat\fR()
- or
- \fIlstat\fR()
- had been called to retrieve the information. Possible values of the
- integer, defined in the
- .IR <ftw.h>
- header, are:
- .IP FTW_D 10
- For a directory.
- .IP FTW_DNR 10
- For a directory that cannot be read.
- .IP FTW_F 10
- For a non-directory file.
- .IP FTW_SL 10
- For a symbolic link (but see also FTW_NS below).
- .IP FTW_NS 10
- For an object other than a symbolic link on which
- \fIstat\fR()
- could not successfully be executed. If the object is a symbolic link
- and
- \fIstat\fR()
- failed, it is unspecified whether
- \fIftw\fR()
- passes FTW_SL or FTW_NS to the user-supplied function.
- .P
- If the integer is FTW_DNR, descendants of that directory shall not be
- processed. If the integer is FTW_NS, the
- .BR stat
- structure contains undefined values. An example of an object that
- would cause FTW_NS to be passed to the function pointed to by
- .IR fn
- would be a file in a directory with read but without execute (search)
- permission.
- .P
- The
- \fIftw\fR()
- function shall visit a directory before visiting any of its
- descendants.
- .P
- The
- \fIftw\fR()
- function shall use at most one file descriptor for each level in
- the tree.
- .P
- The argument
- .IR ndirs
- should be in the range [1,\c
- {OPEN_MAX}].
- .P
- The tree traversal shall continue until either the tree is exhausted,
- an invocation of
- .IR fn
- returns a non-zero value, or some error, other than
- .BR [EACCES] ,
- is detected within
- \fIftw\fR().
- .P
- The
- .IR ndirs
- argument shall specify the maximum number of directory streams or file
- descriptors or both available for use by
- \fIftw\fR()
- while traversing the tree. When
- \fIftw\fR()
- returns it shall close any directory streams and file descriptors it
- uses not counting any opened by the application-supplied
- .IR fn
- function.
- .P
- The results are unspecified if the application-supplied
- .IR fn
- function does not preserve the current working directory.
- .P
- The
- \fIftw\fR()
- function need not be thread-safe.
- .SH "RETURN VALUE"
- If the tree is exhausted,
- \fIftw\fR()
- shall return 0. If the function pointed to by
- .IR fn
- returns a non-zero value,
- \fIftw\fR()
- shall stop its tree traversal and return whatever value was returned
- by the function pointed to by
- .IR fn .
- If
- \fIftw\fR()
- detects an error, it shall return \-1 and set
- .IR errno
- to indicate the error.
- .P
- If
- \fIftw\fR()
- encounters an error other than
- .BR [EACCES]
- (see FTW_DNR and FTW_NS above), it shall return \-1 and set
- .IR errno
- to indicate the error. The external variable
- .IR errno
- may contain any error value that is possible when a directory is opened
- or when one of the
- .IR stat
- functions is executed on a directory or file.
- .SH ERRORS
- The
- \fIftw\fR()
- function shall fail if:
- .TP
- .BR EACCES
- Search permission is denied for any component of
- .IR path
- or read permission is denied for
- .IR path .
- .TP
- .BR ELOOP
- A loop exists in symbolic links encountered during resolution of the
- .IR path
- argument.
- .TP
- .BR ENAMETOOLONG
- .br
- The length of a component of a pathname is longer than
- {NAME_MAX}.
- .TP
- .BR ENOENT
- A component of
- .IR path
- does not name an existing file or
- .IR path
- is an empty string.
- .TP
- .BR ENOTDIR
- A component of
- .IR path
- names an existing file that is neither a directory nor a symbolic link
- to a directory.
- .TP
- .BR EOVERFLOW
- A field in the
- .BR stat
- structure cannot be represented correctly in the current programming
- environment for one or more files found in the file hierarchy.
- .P
- The
- \fIftw\fR()
- function may fail if:
- .TP
- .BR EINVAL
- The value of the
- .IR ndirs
- argument is invalid.
- .TP
- .BR ELOOP
- More than
- {SYMLOOP_MAX}
- symbolic links were encountered during resolution of the
- .IR path
- argument.
- .TP
- .BR ENAMETOOLONG
- .br
- The length of a pathname exceeds
- {PATH_MAX},
- or pathname resolution of a symbolic link produced an intermediate
- result with a length that exceeds
- {PATH_MAX}.
- .P
- In addition, if the function pointed to by
- .IR fn
- encounters system errors,
- .IR errno
- may be set accordingly.
- .LP
- .IR "The following sections are informative."
- .SH EXAMPLES
- .SS "Walking a Directory Structure"
- .P
- The following example walks the current directory structure, calling
- the
- .IR fn
- function for every directory entry, using at most 10 file descriptors:
- .sp
- .RS 4
- .nf
- #include <ftw.h>
- \&...
- if (ftw(".", fn, 10) != 0) {
- perror("ftw"); exit(2);
- }
- .fi
- .P
- .RE
- .SH "APPLICATION USAGE"
- The
- \fIftw\fR()
- function may allocate dynamic storage during its operation. If
- \fIftw\fR()
- is forcibly terminated, such as by
- \fIlongjmp\fR()
- or
- \fIsiglongjmp\fR()
- being executed by the function pointed to by
- .IR fn
- or an interrupt routine,
- \fIftw\fR()
- does not have a chance to free that storage, so it remains
- permanently allocated. A safe way to handle interrupts is to store the
- fact that an interrupt has occurred, and arrange to have the function
- pointed to by
- .IR fn
- return a non-zero value at its next invocation.
- .P
- Applications should use the
- \fInftw\fR()
- function instead of the obsolescent
- \fIftw\fR()
- function.
- .SH RATIONALE
- None.
- .SH "FUTURE DIRECTIONS"
- The
- \fIftw\fR()
- function may be removed in a future version.
- .SH "SEE ALSO"
- .IR "\fIfdopendir\fR\^(\|)",
- .IR "\fIfstatat\fR\^(\|)",
- .IR "\fIlongjmp\fR\^(\|)",
- .IR "\fInftw\fR\^(\|)",
- .IR "\fIsiglongjmp\fR\^(\|)"
- .P
- The Base Definitions volume of POSIX.1\(hy2017,
- .IR "\fB<ftw.h>\fP",
- .IR "\fB<sys_stat.h>\fP"
- .\"
- .SH COPYRIGHT
- Portions of this text are reprinted and reproduced in electronic form
- from IEEE Std 1003.1-2017, Standard for Information Technology
- -- Portable Operating System Interface (POSIX), The Open Group Base
- Specifications Issue 7, 2018 Edition,
- Copyright (C) 2018 by the Institute of
- Electrical and Electronics Engineers, Inc and The Open Group.
- In the event of any discrepancy between this version and the original IEEE and
- The Open Group Standard, the original IEEE and The Open Group Standard
- is the referee document. The original Standard can be obtained online at
- http://www.opengroup.org/unix/online.html .
- .PP
- Any typographical or formatting errors that appear
- in this page are most likely
- to have been introduced during the conversion of the source files to
- man page format. To report such errors, see
- https://www.kernel.org/doc/man-pages/reporting_bugs.html .