📛 NAME
filefuncs - provide some file related functionality to gawk
🚀 Quick Reference
| Use Case | Command | Description |
|---|
| Change directory | chdir(“/path”) | Changes current working directory |
| Get file metadata | stat(“/path”, data) | Fills data array with file stats |
| Traverse directory tree | fts(pathlist, flags, data) | Recursively walk directory tree |
| Get filesystem info | statvfs(“/path”, fsdata) | Fills fsdata array with filesystem statistics |
📋 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 successful,
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 element is only present for device files.
🔢 statdata[“major”]
Corresponds to the
st_major field in the
struct stat. This element is only present for device files.
🔢 statdata[“minor”]
Corresponds to the
st_minor field in the
struct stat. This element 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_PHYSICAL must be provided; otherwise
fts() returns an error value and sets
ERRNO.
- FTS_LOGICAL — Do a “logical” file traversal, where the information returned for a symbolic link refers to the linked-to file, and not to the symbolic link itself. This flag is mutually 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 element 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 entry in the directory. If an entry is a file, that element is as for files, just described. If the entry is a directory, 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 provided 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 returns -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 information 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 natural 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),
read‐
dir(3am),
readfile(3am),
revoutput(3am),
rwarray(3am),
time(3am).
chdir(2),
fts(3),
stat(2),
statvfs(2).
✍️ AUTHOR
Arnold Robbins,
arnold AT skeeve.com.
📜 COPYING PERMISSIONS
Copyright © 2012, 2013, 2018, 2019, Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of this manual page provided the copyright notice and this permission notice are preserved on all copies.
Permission is granted to copy and distribute modified versions of this manual page under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.
Permission is granted to copy and distribute translations of this manual page into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Foundation.
