FILEFUNCS(3am) GNU Awk Extension Modules FILEFUNCS(3am)
NAME
filefuncs - provide some file related functionality to gawk
SYNOPSIS
@load "filefuncs"
result = chdir("/some/directory")
result = stat("/some/path", statdata [, follow])
flags = or(FTS_PHYSICAL, ...)
result = fts(pathlist, flags, filedata)
result = statvfs("/some/path", fsdata)
DESCRIPTION
The filefuncs extension adds several functions that provide access to
file-related facilities.
chdir()
The chdir() function is a direct hook to the chdir(2) system call to
change the current directory. It returns zero upon success or less than
zero upon error. In the latter case it updates ERRNO.
stat()
The stat() function provides a hook into the stat(2) system call. It
returns zero upon success or less than zero upon error. In the latter
case it updates ERRNO. By default, it uses lstat(2). However, if
passed a third argument, it uses stat(2), instead.
In all cases, it clears the statdata array. When the call is success-
ful, stat() fills the statdata array with information retrieved from the
filesystem, as follows:
statdata["name"]
The name of the file, equal to the first argument passed to
stat().
statdata["dev"]
Corresponds to the st_dev field in the struct stat.
statdata["ino"]
Corresponds to the st_ino field in the struct stat.
statdata["mode"]
Corresponds to the st_mode field in the struct stat.
statdata["nlink"]
Corresponds to the st_nlink field in the struct stat.
statdata["uid"]
Corresponds to the st_uid field in the struct stat.
statdata["gid"]
Corresponds to the st_gid field in the struct stat.
statdata["size"]
Corresponds to the st_size field in the struct stat.
statdata["atime"]
Corresponds to the st_atime field in the struct stat.
statdata["mtime"]
Corresponds to the st_mtime field in the struct stat.
statdata["ctime"]
Corresponds to the st_ctime field in the struct stat.
statdata["rdev"]
Corresponds to the st_rdev field in the struct stat. This ele-
ment is only present for device files.
statdata["major"]
Corresponds to the st_major field in the struct stat. This ele-
ment is only present for device files.
statdata["minor"]
Corresponds to the st_minor field in the struct stat. This ele-
ment is only present for device files.
statdata["blksize"]
Corresponds to the st_blksize field in the struct stat, if this
field is present on your system. (It is present on all modern
systems that we know of.)
statdata["pmode"]
A human-readable version of the mode value, such as printed by
ls(1). For example, "-rwxr-xr-x".
statdata["linkval"]
If the named file is a symbolic link, this element will exist and
its value is the value of the symbolic link (where the symbolic
link points to).
statdata["type"]
The type of the file as a string. One of "file", "blockdev",
"chardev", "directory", "socket", "fifo", "symlink", "door", or
"unknown". Not all systems support all file types.
fts()
The fts() function provides a hook to the fts(3) set of routines for
traversing file hierarchies. Instead of returning data about one file
at a time in a stream, it fills in a multi-dimensional array with data
about each file and directory encountered in the requested hierarchies.
The arguments are as follows:
pathlist
An array of filenames. The element values are used; the index
values are ignored.
flags This should be the bitwise OR of one or more of the following
predefined flag values. At least one of FTS_LOGICAL or FTS_PHYS-
ICAL must be provided; otherwise fts() returns an error value and
sets ERRNO.
FTS_LOGICAL
Do a ``logical'' file traversal, where the information re-
turned for a symbolic link refers to the linked-to file,
and not to the symbolic link itself. This flag is mutu-
ally exclusive with FTS_PHYSICAL.
FTS_PHYSICAL
Do a ``physical'' file traversal, where the information
returned for a symbolic link refers to the symbolic link
itself. This flag is mutually exclusive with FTS_LOGICAL.
FTS_NOCHDIR
As a performance optimization, the fts(3) routines change
directory as they traverse a file hierarchy. This flag
disables that optimization.
FTS_COMFOLLOW
Immediately follow a symbolic link named in pathlist,
whether or not FTS_LOGICAL is set.
FTS_SEEDOT
By default, the fts(3) routines do not return entries for
``.'' and ``..''. This option causes entries for ``..''
to also be included. (The AWK extension always includes
an entry for ``.'', see below.)
FTS_XDEV
During a traversal, do not cross onto a different mounted
filesystem.
FTS_SKIP
When set, causes top level directories to not be descended
into.
filedata
The filedata array is first cleared. Then, fts() creates an ele-
ment in filedata for every element in pathlist. The index is the
name of the directory or file given in pathlist. The element for
this index is itself an array. There are two cases.
The path is a file.
In this case, the array contains two or three elements:
"path" The full path to this file, starting from the
``root'' that was given in the pathlist array.
"stat" This element is itself an array, containing the
same information as provided by the stat() function
described earlier for its statdata argument. The
element may not be present if stat(2) for the file
failed.
"error"
If some kind of error was encountered, the array
will also contain an element named "error", which
is a string describing the error.
The path is a directory.
In this case, the array contains one element for each en-
try in the directory. If an entry is a file, that element
is as for files, just described. If the entry is a direc-
tory, that element is (recursively), an array describing
the subdirectory. If FTS_SEEDOT was provided in the
flags, then there will also be an element named "..".
This element will be an array containing the data as pro-
vided by stat().
In addition, there will be an element whose index is ".".
This element is an array containing the same two or three
elements as for a file: "path", "stat", and "error".
The fts() function returns 0 if there were no errors. Otherwise it re-
turns -1.
statvfs()
The statvfs() function provides a hook into the statvfs(2) system call
on systems that supply this system call. It returns zero upon success
or less than zero upon error. In the latter case it updates ERRNO.
When the call is successful, statvfs() fills the fsdata array with in-
formation retrieved about the filesystem, as follows:
fsdata["bsize"]
Corresponds to the bsize member in the struct statvfs.
fsdata["frsize"]
Corresponds to the f_frsize member in the struct statvfs.
fsdata["blocks"]
Corresponds to the f_blocks member in the struct statvfs.
fsdata["bfree"]
Corresponds to the f_bfree member in the struct statvfs.
fsdata["bavail"]
Corresponds to the f_bavail member in the struct statvfs.
fsdata["files"]
Corresponds to the f_files member in the struct statvfs.
fsdata["ffree"]
Corresponds to the f_ffree member in the struct statvfs.
fsdata["favail"]
Corresponds to the f_favail member in the struct statvfs.
fsdata["fsid"]
Corresponds to the f_fsid member in the struct statvfs. This
member is not available on all systems.
fsdata["flag"]
Corresponds to the f_flag member in the struct statvfs.
fsdata["namemax"]
Corresponds to the f_namemax member in the struct statvfs.
NOTES
The AWK fts() extension does not exactly mimic the interface of the
fts(3) routines, choosing instead to provide an interface that is based
on associative arrays, which should be more comfortable to use from an
AWK program. This includes the lack of a comparison function, since
gawk already provides powerful array sorting facilities. While an
fts_read()-like interface could have been provided, this felt less nat-
ural than simply creating a multi-dimensional array to represent the
file hierarchy and its information.
Nothing prevents AWK code from changing the predefined FTS_xx values,
but doing so may cause strange results when the changed values are
passed to fts().
BUGS
There are many more file-related functions for which AWK interfaces
would be desirable.
It's not clear why I thought adding FTS_SKIP was a good idea.
EXAMPLE
See test/fts.awk in the gawk distribution for an example.
SEE ALSO
GAWK: Effective AWK Programming, fnmatch(3am), fork(3am), inplace(3am),
ordchr(3am), readdir(3am), readfile(3am), revoutput(3am), rwarray(3am),
time(3am).
chdir(2), fts(3), stat(2), statvfs(2).
AUTHOR
Arnold Robbins, arnold@skeeve.com.
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Free Software Foundation Feb 21 2018 FILEFUNCS(3am)
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